GRID Training Course
Environmental Protection Agency
Region IV
September 18 - 22,1995
Instructor:
Dave Riddle, Vice-President Technical Services
A.C.T. GIS, Inc.
108 Canvasback Court
Frankfort, Kentucky 40601
Phone: (502) 695-9314
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GRID Training Course
September 16. 1995
Table of Contents
Course Objectives 1
Grid-Cell Concepts 4
What is a grid? 5
Cell Resolution 5
Cell Values 5
Registration of Grids 6
Raster Encoding 6
GRID Basics 7
GRID Overview 7
Types of Grids 7
Grid Attributes 7
GRID Display 9
GRID and AML 9
GRID Analysis 9
Grid Data Input 10
Map Algebra 10
Why Use GRID? 11
GRID Commands 13
Invoking GRID 13
GRID Commands 13
The ABBREVIATIONS Command 13
The AP Command 14
The ARCTOOLS Command 14
The ATUSAGE Command 14
The BUELDSTA Command 14
The BUILDVAT Command 15
The COMMANDS Command 15
The COPY Command 15
The DESCRIBE Command 16
The HELP Command 16
The INFO Command 17
The KILL Command 17
The LISTCOVERAGES Command 17
The LlSTGRIDS Command 17
The LISTIMAGES Command;...: 17
The LISTSTACKS Command 18
The LOG Command..... 18
The PRINTDOC Command 18
The PROJECTCOMPARE Command..: 18
The QUIT Command 19
The RENAME Command 19
The USAGE Command 19
The VERIFY Command 19
ฉ 1995 A.C.T. GIS, Inc. Page i
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GRID Training Course
Saptember 16.1995
Table of Contents (Continued)
The GRID Analysis Environment 20
The SETCELL Command 20
The SETWINDOW Command 20
The SETMASK Command 21
The RESTORE Command 22
The SAVE Command 22
The RESET Command 22
The SHOW Command 22
The STATUS Command 22
Creating GRID Data 23
Grid Conversion Basics 23
ARC GRID Conversion Commands 23
The ARC ASCDGRID Command 24
The ARCADRGGRID Command 25
The ARC DEMLATTICE Command 25
The ARC DTEDGRID Command 26
The ARC FLOATGRID Command 26
The ARC IMAGEGRID Command 27
The ARC LINEGRID Command 28
The ARC MOSSGRID Command 29
The ARC POENTGRID Command 30
The ARC POLYGRID Command 31
The ARC SVFGRID Command 32
The ARC TOPOGRID Command 32
The ARC TOPOGRIDTOOL Command 34
The = Operator 35
GRID Data Conversion Functions 35
The LINEGRID() Function 36
The POINTGRID() Function 37
The POLYGRID() Function 38
GRID Display 39
GRID Display Overview 39
GRID Cell Value Transformation 39
The HISTOGRAM Command 41
Remap Tables 42
Colormap Files 46
The GRID Display Commands 48
The GRIDNODATASYMBOL Command 48
The GRIDPAINT Command 49
The GRIDSHADES Command 50
The GRIDCOMPOSITE Command 51
The GRIDDIRECTION Command 52
The GRIDNET Command 53
ฉ 1995 A.C.T. GIS, Inc. Page ii
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Table of Contents (Continued)
The IMAGE Command 53
The ARCPLOT SHADECOLORRAMP Command 54
The LOADCOLORMAP Command 55
The SAVECOLORMAP Command 55
The CONVERTREMAP Command 56
The CREATEREMAP Command 56
The REMAPGRID Command 57
The SHADEGRID Command 58
Querying Grids 59
The CELLVALUE Command 59
The GREDQUERY Command 60
GRID Terminology 61
GRID Spatial Processing Concepts 62
Location Determination 62
Cell-byCell Processing 62
Multi-grid Calculations 62
Operator and Local Function Processing 62
Neighborhood Processing 62
Neighborhood-notation Processing 62
Zonal Calculations 63
Calculating Distance and Direction 63
Weight-distance Calculations 63
Calculating Area 63
Surface Calculations 64
Map Algebra 65
Map Algebra 65
Map Algebra Expressions 66
GRID Commands 68
Map-algebra Input Types 68
Map-algebra Results 68
Multiple Outputs 69
NOD AT A in GRID 69
Direct Display of Analysis Results 70
GRID Functions 71
Miscellaneous Functions 71
The ABS Function 71
The CEIL Function 72
The CON Function 73
The FLOAT Function 75
The FLOOR Function 76
The FMOD Function 77
The INT Function 78
The ISNULL Function 79
ฉ 1995 A.C.T. GIS, Inc. Page iii
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Table of Contents (Continued)
The MERGE Function 80
The MOSAIC Function 81
The NORMAL Function 82
The PICK Function 83
The RAND Function 84
The SAMPLE Function 85
The SETNULL Function 87
Individual Cell Processing 88
The DOCELL Block 88
The IF Statement 89
The WHILE Statement 91
The SCALAR Function 92
The := Operator 93
Trigonometric Functions 94
Logarithmic and Exponential Functions 95
Statistical Functions 96
Selection Functions 98
The SELECT Function 98
The SELECTBOX Function 100
The SELECTCIRCLE Function 101
The SELECTMASK Function 102
The SELECTPOINT Function 103
The SELECTPOLYGON Function 104
The TEST Function 105
Reclassification Functions 106
The RECLASS Function 106
The SLICE Function ! 108
Shape Analysis Functions 110
The EXPAND Function 110
The REGIONGROUP Function 112
The SHRINK Function 114
The BOUNDARYCLEAN Function 116
The MAJORITYFILTER Function 118
The NIBBLE Function 119
The THIN Function 120
Projecting Grids 121
The PROJECT Function 121
Raster to Vector Conversion 122
The GRIDLENE Function 122
The GREDPOENT Function 123
The GRIDPOLY Function 123
The ARC GRIDASCH Command 124
The ARC GRIDLINE Command 124
ฉ 1995 A.C.T. GIS, Inc. Page iv
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GRID Training Course
September 16.1995
Table of Contents (Continued)
The ARC GRIDPOINT Command 126
The ARC GRIDPOLY Command 126
Focal Functions 127
The FOCALFLOW Function 127
The FOCALMAJORITY Function 128
The FOCALMAX Function 130
The FOCALMEAN Function 132
The FOCALMEDIAN Function 134
The FOCALMIN Function 136
The FOCALRANGE Function 138
The FOCALSTD Function 140
The FOCALSUM Function 142
The FOCALVARIETY Function 144
Zonal Functions 146
The ZONAL ARE A Function 146
The ZONALFTLL Function ; 147
The ZONALGEOMETRY Function 147
The ZONALMAJORTTY Function 147
The ZONALMAX Function 147
The ZONALMEAN Function 148
The ZONALMEDIAN Function 148
The ZONALMIN Function 148
The ZON ALPERIMETER Function 148
The ZONALRANGE Function 149
The ZONALSTATS Function 149
The ZONALSTD Function 149
The ZONALSUM Function 150
The ZONALTHICKNESS Function 150
The ZONALVARIETY Function 150
Surface Analysis 151
Surface Analysis 151
The IDW Function 152
The KRIGING Function 153
The TREND Function 154
The SPLINE Function 154
Surface Defined Grids 155
The SLOPE Function 155
The ASPECT Function 156
The HILLSHADE Function 157
The SAI Command 158
Distance Functions 159
ฉ 1995 A.C.T. GIS, Inc. Page v
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GRID Training Course
September 16.1995
Table of Contents (Continued)
Surface Hydrologic Analysis 160
Surface Hydrologic Analysis 160
DEMs 160
Creating a Depressionless DEM 161
The SINK Function 161
The FILL Command 163
The FLOWDIRECTION Function 164
The FLOW ACCUMULATION Function 165
The FLOWLENGTH Function 166
The BASIN Function 167
The WATERSHED Function 168
The STREAMLINK Function 169
The STREAMLINE Function 169
The STREAMORDER Function 170
The SNAPPOUR Function 170
Groundwater Advection and Dispersion Modeling 171
The DARC YFLOW Function 171
The PARTICLETRACK Function 171
The POROUSPUFF Function 171
Visibility Functions 172
The VISDECODE Command 172
The VISENCODE Command 172
The VISIBILITY Function 172
Grid Stacks 173
The MAKESTACK Command 174
The STACKSHADE Command 174
The COPYSTACK Command 175
The DROPFROMSTACK Command 176
The STACKSTATS Command. 176
AML Directives 177
The &DESCRIBE Directive 177
AML Functions 177
The GETGRID Function 178
The GETIMAGE Function 180
The GETSTACK Function 182
ฉ 1995 A.C.T. GIS, Inc. Page vi
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GRID Training Course September 16, 1995
GRID Training Course Outline
Monday Morning
Introductions
Course Objectives
Grid-Cell Concepts
GRID Basics
GRID Commands
Invoking GRID
GRID Commands
Monday Afternoon
The GRID Analysis Environment
Creating GRID Data
Grid Conversion Basics
ARC GRID Conversion Commands
The = Operator
GRID Data Conversion Functions
Tuesday Morning
GRID Display
GRID Display Overview
GRID Cell Value Transformation
The HISTOGRAM Command
Remap Tables
Colormap Files
GRID Display Commands
Querying Grids
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course
September 16. 1995
GRID Training Course Outline (Continued)
Tuesday Afternoon
GRID Terminology
GRID Spatial Processing Concepts
Map Algebra
Wednesday Morning
GRID Functions
Miscellaneous Functions
Individual Cell Processing
Trigonometric Functions
Logarithmic Functions
Statistical Functions
Wednesday Afternoon
GRID Functions
Selection Functions
Reclassification Functions
Shade Analysis Functions
Projecting Grids
Raster to Vector Conversion
Focal Functions
Zonal Functions
Thursday Morning
Surface Analysis
Surface Analysis Functions
Distance Functions
ฉ1995 A.C.T. GIS, Inc.
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GRID Training Course September 16. 1995
GRID Training Course Outline (Continued)
Thursday Afternoon
Surface Hydrologic Analysis
Groundwater Advection and Dispersion
Friday Morning
Visibility Functions
Grid Stacks
AML Directives and Functions
Friday Afternoon
GRID Workshop
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course September 16.1995
Course Objectives
1. Address GRID-Cell Concepts
2. Address GRID Basics
3. Address Creating GRID Data
4. Address GRID Commands
5. Address the GRID Analysis Environment
6. Address GRID Display and Query
7. Address GRID Terminology
8. Address GRID Spatial Processing Concepts
9. Address Map Algebra
10. Address GRID Functions
11. Address Surface Analysis
12. Address Distance Functions
13. Address Surface Hydrologic Analysis
14. Address Groundwater Advection and Dispersion
15. Address Visibility Functions
16. Address Grid Stacks
17. Address AML Directives and Functions
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course
September 16. 1995
Grid-Cell Concepts
What is a grid?
Grid-based systems divide the world into discrete uniform units
called cells. Every cell represents a specified portion of the
Earth, such as a square mile or a square meter. Each cell is
assigned a value to correspond to the feature or characteristic
that is located at or describes a site, such as elevation, vegetation
cover, or soil type.
Cell Resolution
The cell size chosen for a grid depends on the data resolution
required for the most detailed analysis to be performed.
Data loss occurs when detailed vector boundaries are gridded,
with the amount of loss directly dependent upon the cell size
chosen. Homogeneous areas may be gridded with a larger cell
size.
Cell Values
Cell values categorize a cell. Values may be integer or floating
point.
Four types of cell value measurements are:
1. Ratio - values are derived relative to a fixed zero point on a
linear scale (i.e. age, distance, weight, and volume)
2. Interval - values on a linear scale not relative to a true zero
point (i.e. time of day, years, or temperature).
3. Ordinal - values that determine position (first, second,
third and good, better, best)
4. Nominal - Values used to identify one instance from
another, or to establish a class, group, or category (landuse
code, soil type, and zip codes)
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course
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Grid-Cell Concepts (Continued)
Registration of Grids
Grids must be registered to a common coordinate system before
performing analysis on multiple grids. Each location on the
ground must be represented by the same x,y coordinate on every
grid.
Raster Encoding
The value assigned to a cell depends on the gridding method
used. The four methods for determining cell values are:
1. Centroid - the cell is assigned the value of the feature at
the center of the cell.
Predominant Type (Majority Weighting) - The value of the
feature that fills the majority of the cell is assigned to the
cell.
/ 3.) Most Important - Each cell is assigned the value associated
with the feature that have been specified as most
important to the study.
4. Percentage Breakdown - A cell is assigned several values,
one per feature, according to the percent each feature
occupies within the cell.
ARC/INFO GRID currently supports the predominant type and
most important type methods.
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course
GRID Basics
September 16.1995
GRID Overview
GRID is the ARC/INFO subsystem for creating, analyzing, and
displaying ratser- or cell-based data.
Data in GRID is represented as a series of cells. GRID divides
the data in a particular area into a series of consistent sized rows
and columns, with a value assigned to each cell.
Types of Grids
There are two types of grids, integer and floating point. Integer
grids represent categorical or discrete data such as soil types or
landuse polygons. Floating point grids represent continuous
data such as elevations, noise contours, or radiation levels
relative to a fixed location or emanating point (such as sea level
or a nuclear accident site).
Grid Attributes
In ARC/INFO a grid is similar to a coverage. Each unique grid
cell value has a record in a corresponding value attribute table,
or VAT. A VAT is comparable to a coverage's A AT, PAT, or
NAT.
Only integer grids have a VAT.
When comparing a grid to a polygon coverage, the primary
difference in the attributes is that in a polygon coverage, the
PAT contains one record for each polygon. In a grid, the VAT
contains one record for each unique grid cell value, thus
reducing storage space.
VATs are accessed using INFO just like coverage feature
attribute tables.
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course
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GRID Basics (Continued)
A sample VAT appears below:
Grid: list
Usage: LIST {from} {to} {item...item)
Grid: list mapll.vat
NTT
Record
VALUE
COUNT
1
1
5647
2
2
9940
3
3
828
4
4
116
5
5
1893
6
6
786
7
7
44
8
8
55
9
9
52
10
11
1975
11
12
1372
12
13
7
13
14
1781
14
15
164
15
16
210
16
17
70
17
18
-864
18
19
1034
19
20
145
20
29
1808
21
98
4151
22
99
32794
A VAT contains two attributes by default. These are VALUE
and COUNT. Value is each unique cell value, and COUNT is
the number of cells in the grid having the corresponding cell
value. An example of a VAT follows:
Grid: items
Usage: ITEMS
Usage: ITEMS INFO
Grid: items mapll.vat info
COLUMN ITEM NAME WIDTH OUTPUT
1 VALUE 4 10
2 COUNT 4 10
TYPE N.DEC ALTERNATE NAME INDEXED?
B - Indexed
B
VATs can be modified using such ARC commands as
ADDITEM, DROPITEM, and PULLITEMS.
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course September 16. 1995
GRID Basics (Continued)
GRID allows the storage of a single grid with multiple
attributes to describe the cells. New grids can be derived from
one or more attributes.
GRID Display
Grids can be displayed in Arcplot, and Arcplot commands are
directly accessible from the Grid: prompt or are accessible by
prefixing the Arcplot command with AP (when command names
are the same between Arcplot and GRID but have different
functions). Various Arcplot commands specifically display
grids.
GRID and AML
AMLs can be created to operate within GRID, just like any other
ARC/INFO module. All AML functions, directives, and menus
are available within GRID.
GRID Analysis
Functions are grouped into four categories:
1. Local - per-cell computation of an output grid based on
input cell value at each location. Examples include adding
two grids together to create a new output grid, selecting all
cell values equal to a value and writing them to an output
grid, or changing all unique grid cell values to new unique
output cell values.
2. Focal - per-neighborhood computation of an output grid
based on the values of cells in a neighborhood (the input
cell and its surrounding cells). Neighborhoods can be the
3x3 cell neighborhood, an extended neighborhood (i.e.
10x10 cells, etc.), or a circular, wedge, or donut shaped
neighborhood. Examples include sum, mean, and
standard deviation of cells in a neighborhood.
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course
September 16. 1995
GRID Basics (Continued)
3. Zonal - per-zone computation of output cell values based
on values of cells in a zone (all cells with the same value in
a grid). Examples include mean, sum, min, max, or range
computations.
4. Global - per-grid computation of output cell values based
on all cell values in a grid. Examples include surface
modeling, Euclidean distance, groundwater, weighted
distance, hydrologic, and multivariate functions.
GRID analysis can be performed on grids with different
resolutions (cell sizes). GRID^automatically resamples^the grids
to the coarsest cell size before processing.
When insufficient information is available to assign a value to a
cell, the cell can be assigned a NOD ATA value. All GRID
analyses are desired to handle NOD ATA cells.
iV
GRID Data Input
Data can be input into GRID in one of the following ways:
1. Coverage to grid conversion (points, lines, or polygons)
2. Lattice to grid conversion
3. Image to grid conversion
4. ASCII file to grid conversion
5. Floating point binary file to grid conversion
6. ADRG, DTED, or SVF data to grid conversion
7. DEM to lattice conversion
Map Algebra
Map algebra is a data manipulation language using by GRID to
perform spatial analysis using grid data.
GRID provides a wide number of functions used to process grid
data.
1995 A.C.T. GIS, Inc.
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GRID Training Course
September 16. 1995
GRID Basics (Continued)
GRID supports various operators which compute on one or
more input grids. Operators include:
1. Arithmetic
2. Boolean
3. Relational
4. Bitwise
5. Combinatorial
6. Logical
7. Accumulative
8. Assignment
DOCELL loops allow for conditional and interactive control of
grid cell values on a cell by cell basis.
Why Use GRID?
GRID has the ability to represent continuos data such as
surfaces that cannot be represented with a vector data structure.
GRID can store point, line, polygon, and surface data in a
common format, allow analysis of all data types simultaneously.
Some accuracy might be lost when representing data in a grid
format. Polygons, for example, might become generalized when
converted to grid. The cell resolution determines how
accurately a feature will be represented as a grid.
Some application well suited for GRID include:
1. Hydrologic Analysis
2. Determination of Subbasin Area Statistics
3. Determination of Runoff Coefficients
4. Computation of Subbasin Precipitation
5. Spatial Display of Erosion and Sediment Disposition
6. Tracking Pollution Dispersion
7. Environmental Analysis
8. Habitat Suitability
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course
September 16. 1995
GRID Basics (Continued)
GRID should be used when:
1. Representing the locational view of geographic data of
both continuous surfaces as well as categorical data.
2. Modeling of attributes of locations on the Earth's surface
3. Working with multiple data types in the same
environment
GRID is best when:
1. The attributes of a location are influenced by the attributes
of the locations that surround it (i.e. pH varies depending
of the pH of surrounding areas; visual preference depends
on positive and negative visual effects in an area;
population changes over time due to the composition of
the surrounding population)
2. The attributes of a location are influenced by where its
position falls within another feature (i.e. locating optimal
habitat; preventing a disease outbreak; or examining
roughness of terrain for determining a building site.
3. Cell-based systems can be used for continuous surface-
data modeling (i.e. modeling noise in decibels at different
locations from a proposed airport; determining areas
affected by a solid waste dump)
4. Optimal allocation and surface determinations that can
only be calculated when a surface is divided into discrete
units (i.e. determining the optimal course for a new road
based on soil types; creating a drainage map from a
elevation surface; or identifying locations along a road that
should be preserved for a visual quality assessment study)
Vector data is better suited when objects are more important
than location.
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course September 16. 1995
GRID Commands
Invoking GRID
GRID is invoked from the Arc: prompt by typing grid. For
example:
Arc: grid
GRID Commands
The following commands are available from the Grid: prompt:
M < A Co
ฃ
ABBREVIATIONS
ADDTOSTACK
AP
ARCTOOLS
ATUSAGE
BUILDSTA
BUILDVAT
CELLVALUE
CLASSSAMPLE
COMMANDS
CONVERTREMAP
COPY
COPYSTACK
CORRELATION
CREATEREMAP
DENDROGRAM
DESCRIBE
DRAWSIG
DRAWZONESHAPE
DROPFROMSTACK
EXTERNAL
EXTERNALALL
FILL
FORMEDIT
GEARY
GRIDCOMPOSITE
GRIDEDIT
GRIDNODATASYMBOL
GRIDPAINT
GRIDQUERY
GRIDSHADES
HELP
HISTOGRAM
IMAGE
INDEX ITEM
INFO
KILL
LIST
LISTCOVERAGES
LISTGRIDS
LISTIMAGES
LISTSTACKS
LLSFIT
LOADCOLORMAP
LOG
MAKESTACK
MERGEVAT
MORAN
PRINT
PRINTDOC
PROJECTCOMPARE
QUIT
REGRESSION
REMAPGRID
REMOVESCALAR
RENAME
RESET
RESTORE
SAI
SAVE
SAVECOLORMAP
SCATTERGRAM
SETCELL
SETMASK
SETWINDOW
SHADEGRID
SHOW
STACKHISTOGRAM
STACKSCATTERGRAM
STACKSHADE
STACKSTATUS
STATUS
USAGE
VERIFY
VISDECODE
VISENCODE
The following section describes some of the more commonly
used GRID commands.
The ABBREVIATIONS Command
Turns command abbreviations on or off.
Usage: ABBREVIATIONS
means all the characters in a GRID function or command
name must be entered.
means function and command names may be
abbreviated.
Abbreviations are OFF when GRID is invoked.
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course September 16.1995
GRID Commands (Continued)
The AF Command
Allows entry of Arcplot commands directly from the Grid:
prompt.
Usage: AP
AP is only needed for those commands that share the same
name in Arcplot and GRID but behave differently (i.e. RESET,
LIST, and USAGE). All other Arcplot commands are accessible
from the Grid: prompt.
The ARCTOOLS Command
Invokes the ArcTools menu interface.
Usage: ARCTOOLS {MAP I EDIT I GRID I COMMAND}
The ATUSAGE Command
Displays the usage of an ATOOL command
Usage: ATUSAGE
The BUILDSTA Command
Builds a statistics file (STA) for a grid based upon the VALUE
item.
Usage: BUILDSTA
A statistics file is useful for some GRID commands which need
information about distribution of data such as GRIDSHADES
and GRIDPAINT.
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course September 16. 1995
GRID Commands (Continued)
The BUILD VAT Command
Build a value attribute table (VAT) for a grid.
Usage: BUILDVAT
If a VAT does not exist, BUILDVAT creates a VAT with the
items VALUE and COUNT. Otherwise, all items in the VAT are
retained.
The COMMANDS Command
Displays GRID functions, commands, and ATOOL commands
Usage: COMMANDS {prefix I wildcard}
When the COMMANDS command is executed, GRID command
names are followed by "**" and function names are followed by
(). Operators are listed at the end just before GRID ATOOL
commands.
The COPY Command
Duplicates a grid or other ARC/INFO geo_dataset.
Usage: COPY {to_geo_dataset}
COPY may be executed from both the Arc: and Grid: prompts.
The {to_geo_dataset} is optional and if is in
another workspace, the geo_dataset is copied to the current
workspace with the same geo_dataset name.
The {to_geo_dataset} cannot exist in the current workspace.
All INFO files with . are copied as
well.
ฉ 1995 A.C.T. GIS, Inc.
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GRID Commands (Continued)
The DESCRIBE Commands
Provides a description of a grid or other ARC/INFO geo_dataset.
Usage: DESCRIBE
DESCRIBE may be executed from both the Arc: and Grid:
prompts.
The following example illustrates the DESCRIBE command:
Grid: describe railgrid
Description of Grid /ACT/RIDDLE/FORESITE/WORK1/RAILGRID
Cell Size = 208.710
Number of Rows = 577
Number of Columns = 359
Data Type: Integer
Number of Values = 2
Attribute Data (bytes) = 8
BOUNDARY
STATISTICS
Xmin =
Xmax =
Ymin =
Ymax =
Projection
Zone
Datum
Units
Parameters:
Grid:
2792269.645
2867196.652
185845.614
306271.471
Minimum Value =
Maximum Value =
Mean =
Standard Deviation =
0.000
1.000
0.009
0.094
COORDINATE SYSTEM DESCRIPTION
STATEPLANE
5376
NAD27
FEET Spheroid CLARKE1866
The HELP Command
Invokes ArcDOC, the on-line ARC/INFO documentation.
Usage: HELP
ฉ 1995 A.C.T. GIS, Inc.
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GRID Training Course September 16. 1995
GRID Commands (Continued)
The INFO Command
Starts the INFO subsystem from within GRID.
Usage: INFO {info_directory}
The KILL Command
Deletes a grid.
Usage: KILL {ARC I INFO I ALL}
KILL may be executed from both the Arc: and Grid: prompts.
The LISTCOVERAGES Command
ฎ Lists the coverages present in a workspace.
Usage: LISTCOVERAGES {workspace}
LISTCOVERAGES may be executed from the Arc: and Grid:
prompts.
The LISTGRIDS Command
Lists the grids present in a workspace.
Usage: LISTGRIDS {workspace}
LISTGRIDS may be executed from the Arc: and Grid: prompts.
The LISTIMAGES Command
Lists the images present in a workspace.
Usage: LISTIMAGES {workspace} {NOFORMAT I FORMAT}
LISTIMAGES may be executed from the Arc: and Grid: prompts.
{NOFORMAT I FORMAT} specifies whether the image formats
are listed. By default, no formats are listed.
ฉ 1995 A.C.T. GIS, Inc. Page 17
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ft RID Training Course September 16. 1995
GRID Commands (Continued)
The LISTSTACKS Command
Lists the grid stacks present in a workspace.
Usage: LISTSTACKS {workspace}
LISTSTACKS may be executed from the Arc: and Grid: prompts.
The LOG Command
Lists the contents of a LOG file or adds a new entry to the LOG.
Usage: LOG {LIST I ADD}
LOG * displays the workspace LOG file.
{LIST} is the default. The LOG file is listed. {ADD} allows a
comment line to be added to the LOG file. The user is prompted:
Enter comment line:
Simply enter the desired comment and press .
The PRINTDOC Command
Invokes the ArcDOC Print Tool menu which allows any portion
of ArcDOC to be selected and printed.
Usage: PRINTDOC
The PROIECTCOMPARE Command
Sets the level of comparison between projection files for the
current session.
Usage: PROJECTCOMPARE
means projection aren't compared. {PARTIAL} means
at least one projection file must be defined. {FULL} means both
projection files must be defined identically.
ฉ 1995 A.C.T. GIS, Inc.
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GRID Commands (Continued)
The QUIT Command
Stops execution of GRID and returns the user to the Arc:
prompt.
Usage: QUIT
The RENAME Command
Renames a grid or other ARC/INFO geo_dataset.
Usage: RENAME
RENAME may be executed from the Arc: and Grid: prompts.
The USAGE Command
Returns the usage of an GRID command or function.
Usage: USAGE
The VERIFY Command
Sets the automatic verification of answers to system prompts.
Usage: VERIFY
means an error message will be returned and the
process will terminate.
prompts for verification to delete or overwrite protection
on data.
means data will be deleted or overwritten without the
user being prompted for verification.
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A.
The GRID Analysis Environment
The following GRID commands are used to set the GRID analysis
environment:
J
/)H
The SETCELL Command ^ ^
\> r .< r
' \ ^ V
c?
\
Sets the cell size of the current analysis environment.
Usage: SETCELL {MAXOF I MINOF I cellsize I grid}
{MAXOF} is the default. J It sets the cell size to the maximum of
all inputs.
{MINOF} sets the cell size to the minimum of all inputs.
{cellsize} sets the cell size to a real number in map units.
{grid} sets the cell size to cell size of an existing grid.
All GRID functions and operators respect the set cell size.
Use the Grid: SHOW SETCELL command to list the current cell
size.
The Shi WINDOW Command
Sets the window of the current analysis environment.
Usage: SETWINDOW
Usage: SETWINDOW
{snap_grid}
sets the window to the maximum of all inputs.
sets the window to the minimum of all inputs.
sets the window to the extent of a grid.
sets the window to the extent of a cover.
sets the window to a specified box
in map units.
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The GRID Analysis Environment (Continued)
The SETWINDOW Command (Continued)
{snap_grid} is a grid that serves as the base for snapping corner
coordinates. It is used with the
option to ensure that a subset area will match accurately with
the original grid. The window is snapped to the closest lower
left cell and closest upper right cell in {snap_grid}.
A graphics window must be active using DISPLAY to use the *
option.
The window is for analysis purposes only. It is not a display
window and does not affect the display of grids.
A) Use the Grid: SHOW SETWINDOW command to list the current
y\ SETWINDOW setting.
The SETMASK Command
Sets the mask of the current analysis environment.
Usage: SETMASK
OFF turns off the use of a mask.
is the name of a grid used as a mask.
A mask allows processing to be performed only for cells in the
analysis window overlapped by the mask grid.
The SELECTO function can be used to select all cells which will
serve as a mask. Cells should be assigned NODATA where
processing should not occur. The SELECTO functions sets all
unselected cells to NODATA.
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GRID Training Course . September 16.1995
The GRID Analysis Environment (Continued)
The RESTORE Command
Restores the analysis environment to the settings in an
environment file.
Usage: RESTORE
The SAVE Command
Saves the current analysis environment to a file.
Usage: SAVE
The is an ASCII text file.
The RESET Command
Reinitializes the GRID analysis environment to the defaults.
Usage: RESET
The SHOW Command
Lists the current setting of the user workspace.
Usage: SHOW
Commands which are arguments for SHOW in GRID are
ABBREVIATIONS, PROJECTCOMPARE, SCALAR
/ SETCELL, SETMASK, SETWINDOW, and
VERIFY.
The STATUS Command
Shows the status of the current analysis environment.
Usage: STATUS
Displays the current settings for cell size, window, mask, and
abbreviations.
ฉ 1995 A.C.T. GIS, Inc.
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Creating GRID Data
Grid Conversion Basics
The main source for GRID data is existing ARC/INFO
coverages.
DXF files and IGDS files can be converted to coverages, thus
serving as another source for GRID.
DTED, ADRG, images, and DEMs may also be converted
directly to GRID.
The main factors to consider when converting data is GRID is
cell resolution, georeferencing images, and the coverage item
used to define cell values.
Cell size should be determined from input data resolution, the
resulting database size and disk capacity, the desired response
time since large grids take longer to process, and the types of
analysis to be performed.
A cell size finer that the resolution will not produce more
accurate results.
Since all grids must be in the same projection to be analyzed
together, grids and lattices may be projected with the PROJECT
command. Images may be georeferenced using the
CONTROLLPOINTS, WARP, and ADJUST commands.
Grids may also be converted to images, DEMs, or coverages.
ARC Grid Conversion Commands
The following ARC commands can be used to convert coverages
into grids:
ฉ1995 A.C.T. GIS, Inc.
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Creating GRID Data (Continued)
The ARC ASCIIGRID Command
Converts an ASCII file to a grid.
Usage: ASCIIGRID {INT I FLOAT}
must contain header information consisting of a
set of keywords, followed by cell values in a row-major order.
The file format required is:
cncols xxx>
cnrows xxx>
{nodata_value xxx}
rowl
row2
row n
where xxx is a number, the keyword nodata_value is optional
and defaults to -9999. Row 1 of the grid is at the top of the grid,
row 2 is just below, and so on. Cell values are delimited by
spaces. The number of columns in the header is to determine
where a new row begins.
The number of cell values must be equal to the number of rows
times the number of columns, or an error will be returned.
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Creating GRID Data (Continued)
The ARC ADRGGRID Command
Converts Arc Digitized Raster Graphics (ADRG) image data into
a grid.
Usage: ADRGGRID {in_band}
{ALL I BOX} {xmin} {ymin} {xmax} [ymax}
{in_band} is an optional image band number. Band 1 is red, 2 is
green, and 3 is blue.
{ALL I BOX) {xmin} {ymin} {xmax} [ymax} are keywords used to
specify if the entire image or a portion of the image is to be
converted.
The ARC DEMLATTICE Command
Converts a DEM in USGS or TAME format to a lattice.
Usage: DEMLATTICE {USGS I TAME} {z_factor}
{USGS} specifies the DEM is in USGS 7.5 minute, 1 degree, or
other file in USGS DEM format.
{TAME} specifies the DEM is in the Terrain Access Made Easy
(TAME) format, the standard format for SPOT DEM data.
{z_factor} is the number of ground x,y units in 1 surface ZUNIT.
The ZUNIT value is multiplied by the {z_factor} to adjust the
out_lattice to some other unit of measure (possibly to convert
from feet to meters or vice versa).
A lattice is implemented as a point grid.
USGS DEMs are not immediately suitable for volume, slope, or
visibility analysis because the x,y locations are stored in latitude
and longitude and the z values are measured in meters. To
convert the z values to feet, use a {z_factor} of 3.280833, and/or
PROJECT the lattice to the desired projection.
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Creating GRID Data (Continued)
The ARC DTEDGRID Command
Converts a US DMA DTED file into a grid.
Usage: DTEDGRID
is the United States Defense Mapping Agency
Digital Terrain Elevation file.
At latitudes greater than 50 degrees, the DTED data is no longer
square cells. The data is resampled using bilinear interpolation
to create square grid cells.
The Y,X column/row orientation of the DTED data is converted
to the row/column (X,Y) format for grid.
DTED data is published in decimal degrees and the vertical unit
of measure is meters.
The ARC FLOATGRID Command
Converts a file of binary floating point numbers into a grid.
Usage: FLOATGRID
is an IEEE floating point format, 32 bit signed binary
file.
An ASCII .hdr header file is required in addition to the
binary data file.
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Creating GRID Data (Continued)
The ARC IMAGEGRID Command
Converts an image into a grid or set of grids.
Usage: IMAGEGRID {out_colormap._file} {in_band}
{NEAREST I BILINEAR I CUBIC} {DEFAULT I SQUARE}
can be a BIL, BIP, BSQ, ERDAS, IMAGINE,
GRASS, RLC, SUNRASTER, ADRG, or TIFF image.
{out_colormap_file} is an ASCII colormap file created for
pseudocolor images.
{in_band} is the optional band number.
{NEAREST} is the nearest neighbor resampling algorithm. It
calculates the value of the output cell by assigning it the value
of the nearest pixel in the input image. This is the default.
{BILINEAR} is the bilinear interpolation resampling algorithm.
It calculates the value of the output cell by interpolating from
the values of the four nearest pixels in the input image based
upon the weighted distance to these pixels.
{CUBIC} is the cubic convolution resampling algorithm. It
calculates the value of each output cell in the same manner as
bilinear, except that the weighted values of the 16 nearest pixels
in the input image are used.
{DEFAULT} means the output grid is optimized for use with
GRID.
{SQUARE} means the output grid is optimized for use with
ARCSCAN.
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Creating GRID Data (Continued)
The ARC LINEGRID Command
Creates a grid from line features in an ARC/INFO coverage.
Usage: LINEGRID {value_item}
{lookup_table} {weight_table}
{value_item} is an item in the coverage AAT used to assign codes
to the grid. By default the internal arc number will be used.
The item must be numeric.
{lookup_table} is an INFO table used to define grid cell values.
The table must contain the items {value_item} and CODE.
CODE must be defined as numeric. The table must be sorted in
ascending order on {value_item}.
{weight_table} is an INFO table used to assign weights to grid
cell codes. These weights are used to resolve cases when a
single cell can have several possible values. The table must
have two items: CODE and WEIGHT. Both items must be
defined as numeric data types. The CODE with the highest
WEIGHT will be assigned to the cell. If a CODE is not present,
a weight of 0 is assigned.
LINEGRID has two prompts. The first is:
Cell Size (square cell):
This is the cell size in map units. The second prompt is:
Convert the Entire Coverage (Y/N)? :
Enter Y or N. If N is entered, the additional prompts are:
Grid Origin (x,y):
Enter the x,y coordinate of the origin in map units.
Then the following prompt appears:
Grid Size (nrows, ncolumns):
Enter the number of rows and columns of cells.
Background value (NODATA/ZERO):
Enter the value of cells not overlaying line features in the grid.
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Creating GRID Data (Continued)
A samples execution of LINEGRID follows:
Arc: linegrid
Usage: LINEGRID {value_item} {lookup_table}
{weight_table}
Arc: linegrid railroadl railgrid railroad-code
Converting arcs from railroadl to grid railgrid
Cell Size (square cell): [SQRT 43560]
Convert the Entire Coverage(Y/N)?: y
Enter background value (NOD AT A I ZERO): zero
Number of Rows = 577
Number of Columns = 359
Percentage of Gridded Cells...100%
Arc: describe railgrid
Description of Grid /ACT/RIDDLE/FORESITE/WORK1/RAILGRID
Cell Size = 208.710 Data Type: Integer
Number of Rows = 577 Number of Values = 2
Number of Columns = 359 Attribute Data (bytes) = 8
BOUNDARY STATISTICS
Xmin = 2792269.645 Minimum Value = 0.000
Xmax = 2867196.652 Maximum Value = 1.000
Ymin = 185845.614 Mean = 0.009
Ymax = 306271.471 Standard Deviation = 0.094
COORDINATE SYSTEM DESCRIPTION
Projection STATEPLANE
Zone 5376
Datum NAD27
Units FEET Spheroid CLARKE1866
Parameters:
Arc:
The ARC MOSSGRID Command
Creates a grid from a MOSS raster export file.
Usage: MOSSGRID
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Creating GRID Data (Continued)
The ARC POINTGRID Command
Creates a grid from point features in an ARC/INFO coverage.
Usage: POINTGRID {value_item}
{lookup_table} {weight_table}
{value_item} is an item in the coverage PAT used to assign codes
to the grid. By default, the internal point number will be used.
The item must be numeric.
{lookup_table} is an INFO table used to define grid cell values.
The table must contain the items {value_item} and CODE.
CODE must be defined as numeric. The table must be sorted in
ascending order on {value_item}.
{weight_table} is an INFO table used to assign weights to grid
cell codes. These weights are used to resolve cases when a
single cell can have several possible values. The table must
have two items: CODE and WEIGHT. Both items must be
defined as numeric data types. The CODE with the highest
WEIGHT will be assigned to the cell. If a CODE is not present,
a weight of 0 is assigned.
POINTGRID has two prompts. The first is:
Cell Size (square cell):
This is the cell size in map units. The second prompt is:
Convert the Entire Coverage (Y/N)? :
Enter Y or N. If N is entered, the additional prompts are:
Grid Origin (x,y):
Enter the x,y coordinate of the origin in map units.
Then the following prompt appears:
Grid Size (nrows, ncolumns):
Enter the number of rows and columns of cells.
Background value (NODATA/ZERO):
Enter the value of cells not overlaying point features in the grid.
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Creating GRID Data (Continued)
The ARC POLYGRID Command
Creates a grid from polygon features in an ARC/INFO coverage.
Usage: POLYGRID {value_item}
{lookup_table} {weight_table}
{value_item} is an item in the coverage PAT used to assign codes
to the grid. By default, the internal polygon number will be
used. The item must be numeric.
{lookup_table} is an INFO table used to define grid cell values.
The table must contain the items {value_item} and CODE.
CODE must be defined as numeric. The table must be sorted in
ascending order on {value_item}.
{weight_table} is an INFO table used to assign weights to grid
cell codes. These weights are used to resolve cases when a
single cell can have several possible values. The table must
have two items: CODE and WEIGHT. Both items must be
defined as numeric data types. The CODE with the highest
WEIGHT will be assigned to the cell. If a CODE is not present,
a weight of 0 is assigned.
POLYGRID has two prompts. The first is:
Cell Size (square cell):
This is the cell size in map units. The second prompt is:
Convert the Entire Coverage (Y/N)? :
Enter Y or N. If N is entered, the additional prompts are:
Grid Origin (x,y):
Enter the x,y coordinate of the origin in map units.
Then the following prompt appears:
Grid Size (nrows, ncolumns):
Enter the number of rows and columns of cells.
Background value (NODATA/ZERO):
Enter the value of cells not overlaying polygon features in the grid.
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Creating GRID Data (Continued)
The ARC SVFGRID Command
Converts an ARC/INFO single variable file into a grid.
Usage: SVFGRID
is the single variable file to be converted. SVF
files were the grid files from ESRI's original PIOS and GRID
software from the 1980's.
and are the x and y coordinate of the lower left
corner of the SVF file in map units.
o is the cell width of the SVF file in map units.
is the cell height of the SVF file in map units.
If the cell width and cell height are different, the SVF is
resampled to create square grid cells.
Only integer grids may be created with the SVFGRID command.
The ARC TOPOGRID Command
Generates a hydrologically correct grid of elevation from point,
line, and polygon coverages.
Usage: TOPOGRID
is the cell size of the output grid in map units.
The TOPOGRID command is similar to PROJECT and provides
a TopoGrid: prompt.
Various subcommands are available at the TopoGrid: prompt.
These are:
BOUNDARY which is a polygon coverage that
defines the boundary of the output grid.
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Creating GRID Data (Continued)
The ARC TOPOGRID Command (Continued)
COMMANDS {prefix} lists the available subcommands.
DATATYPE is the primary type of input
data.
END concludes the specification of subcommands.
ENFORCE turns the drainage enforcement routine
on or off.
ITERATIONS is the maximum number of iterations of
each grid resolution.
LIST lists the current setting of all subcommands.
MARGIN is the distance in map units to interpolate the
specified XYZLIMITS. The default is 0.
OUTPUTS {sink_cover} {drainage_cover} {diagnostic_file}
provides optional output information that can be used to
evaluate the output elevation grid.
POINT is a point cover representing
surface elevations.
QUIT quits the TOPOGRID command without creating output.
RESET resets all parameters to their default values.
SINK allows input of a point cover
representing a known topographic depression.
STREAM is line coverage representing streams.
TOLERANCES {rms} {toll} {tol2} is a set of tolerances used to
adjust the calculate the drainage enforcement process. The
default tolerances are 0.5, 2.5, and 10.
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Creating GRID Data (Continued)
The ARC TQPOGRID Command (Continued)
XYZLIMITS {xmin} {ymin} {xmax} {ymax} {zmin} {zmax} are the
limits of the input data to be used to create the grid.
The TOPOGRIDTOOL is a menu interface for the TOPOGRID
command.
The ARC TOPOGRIDTOOL Command
TOPOGRID creates a hydrologically correct digital elevation
model from comparatively small but well selected elevation and
stream coverages. It is based upon the ANUDEM program
developed by Michael Hutchinson.
Usage: TOPOGRIDTOOL
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Creating GRID Data (Continued)
The = Operator
Creates a new output grid from an input grid, scalar, number, or
expression.
Usage: =
is an output integer or floating point grid. The grid
must not already exist.
A generic grid expression would be coutput = result of input>
where result of input may be a mathematical expression or
GRID function.
GRID functions perform some type of analysis and create some
type of output, usually a new grid. An expression in the form
= ) must be
given to save the output of a function to a new grid.
are the list of required and optional
arguments for each function separated by commas.
Functions may be nested inside one another. The result of the
innermost function serves as the input for the surrounding
function and so on.
A scalar is the current value of a specified scalar variable. A
scalar is a variable in GRID to which a value may be assigned.
Scalars may be used in expressions such as:
outgrid = ingrid +
GRID Data Creation Functions
The following functions are available at the Grid: prompt in
order to convert line, point, and polygon coverages to a grid.
ฉ 1995 A.C.T. GIS, Inc.
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Creating GRID Data (Continued)
The LINEGRIDOFunction
Creates a grid from line features in an ARC/INFO coverage.
Usage: LINEGRID(, {item}, {lookup_table},
{weight_table}, , {NODATA I ZERO})
is the input line coverage.
{item} is the an item in the coverage AAT used to assign codes to
the grid. By default, the internal arc number will be used. The
item must be numeric.
{lookup_table} is an INFO table used to define grid cell values.
The table must contain the items {item} and CODE. CODE must
be defined as numeric. The table must be sorted in ascending
order on {value_item}.
{weight_table} is an INFO table used to assign weights to grid
cell codes. These weights are used to resolve cases when a
single cell can have several possible values. The table must
have two items: CODE and WEIGHT. Both items must be
defined as numeric data types. The CODE with the highest
WEIGHT will be assigned to the cell. If a CODE is not present,
a weight of 0 is assigned.
is the output grid cell size.
{NODATA I ZERO} is the background value assigned to cells in
which line features do not exist.
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Creating GRID Data (Continued)
The POINTGRIDOFunction
Creates a grid from point features in an ARC/INFO coverage.
Usage: POINTGRID(, {item}, {lookup_table},
{weigh t_table}, / {NODATA I ZERO})
is the input line coverage.
{item} is the an item in the coverage PAT used to assign codes to
the grid. By default, the internal point number will be used.
The item must be numeric.
{lookup_table} is an INFO table used to define grid cell values.
The table must contain the items {item} and CODE. CODE must
be defined as numeric. The table must be sorted in ascending
order on {value_item}.
{weight_table} is an INFO table used to assign weights to grid
cell codes. These weights are used to resolve cases when a
single cell can have several possible values. The table must
have two items: CODE and WEIGHT. Both items must be
defined as numeric data types. The CODE with the highest
WEIGHT will be assigned to the cell. If a CODE is not present,
a weight of 0 is assigned.
is the output grid cell size.
{NODATA I ZERO} is the background value assigned to cells in
which point features do not exist.
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Creating GRID Data (Continued)
The POLYGRIDOFunction
Creates a grid from polygon features in an ARC/INFO coverage.
Usage: POLYGRID(/ {item}, {lookup_table},
{weight_table}, )
is the input line coverage.
{item} is the an item in the coverage PAT used to assign codes to
the grid. By default, the internal polygon number will be used.
The item must be numeric.
{lookup_table} is an INFO table used to define grid cell values.
The table must contain the items {item} and CODE. CODE must
be defined as numeric. The table must be sorted in ascending
order on {value_item}.
{weight_table} is an INFO table used to assign weights to grid
cell codes. These weights are used to resolve cases when a
single cell can have several possible values. The table must
have two items: CODE and WEIGHT. Both items must be
defined as numeric data types. The CODE with the highest
WEIGHT will be assigned to the cell. If a CODE is not present,
a weight of 0 is assigned.
is the output grid cell size.
ฉ 1995 A.C.T. GIS, Inc.
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Displaying Grids
GRID Display Overview
Displaying grids is much like displaying coverages. Arcplot
commands are available from the Grid: prompt which allows
grids to be displayed and hardcopy output to be generated with
having to leave the GRID module.
It is assumed that users are familiar with the display, query, and
hardcopy map generation capabilities of Arcplot. There are
simply a few new commands which are needed for specifically
displaying grids in Arcplot or GRID.
The DISPLAY device must be define before a grid can be
displayed.
The MAPEXTENT must be set to one or more grids before a grid
can be displayed.
Grid Cell Value Transformation
There are two concepts for displaying grids.
1. Grid values can be transformed through stretching or the
use of a remap table.
2. Transformed grid cell values can be passed to a shadeset
or an ASCII colormap file which specifies the color
associated with each transformed cell value.
A cell value transformation is graphical and does not change the
actual grid.
To display a grid, the cell values can be transformed either
through a stretch or reclassification. Cell values are converted
into symbol numbers.
If cell values are equal to symbol number values in a shadeset,
no transformation is needed. Invoke GRID and try the
following example:
ฉ 1995 A.C.T. GIS, Inc.
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Displaying Grids (Continued)
Grid Cell Value Transformation (Continued)
Grid: arc generate gridcovl6
Generate: fishnet
Fishnet Origin Coordinate (X,Y): 0,0
Y-Axis Coordinate (X,Y): 0,4
Cell Size (Width,Height): 1,1
Number of Rows, Columns: 4,4
Generate: quit
Externalling BND and TIC...
Grid: arc build gridcovl6 poly
Building polygons-
Grid: disp 9999 3
Grid: polygrid
Usage: (*) POLYGRID(,{item},{lookup_table},{weight_table},{cellsize})
Grid: setcell 1
Grid: gridl6 = polygrid(gridcovl6, gridcovl6-id)
Converting polygons from GRIDCOV16 to grid GRID16
Number of Rows - 4
Number of Columns = 4
Percentage of Gridded Cells...100%
Grid: mape gridl6
Grid: shadeset color
Grid: gridpaint gridl6
Grid: arclines gridcovl6 1
Grid: polygontext gridcovl6 gridcovl6-id
Grid:
In this example/ a 4x4 polygon coverage is generated with
GENERATE, and topology created with BUILD. Within GRID,
the coverage is converted to a grid using the POLYGRIDO
function using the cover-id's as cell values. Then the grid is
drawn with the GRIDPAINT command using SHADESET
COLOR. The cells are shaded with each symbol in
COLOR.SHD. In this example, no transformation of cell values
is needed.
ฉ 1995 A.C.T. GIS, Inc.
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Displaying Grids (Continued)
Grid Cell Value Transformation (Continued)
Stretching of cell values is commonly done to continuous grids
such as an elevation surface in order to display elevations as
continuous shades of gray. Values are stretched from 0 to 255.
Two types of stretches are linear and equal-area.
A linear stretch rescales the cell values from their original range
to a range from 0 to 255 (which is the maximum number of
colors that can be simultaneously displayed on an 8-bit color
device).
An equal-area stretch also rescales the cell values from 0 to 255,
but the difference is that the values are distributed so that an
equal number of cells are assigned to each of the 256 possible
values. An equal-area stretch requires a VAT and thus cannot
be used with floating point grids.
The HISTOGRAM command can be used to view a graph
indication the frequency distribution of values in a GRID. The
DESCRIBE command can be used to determine the range of cell
values (Minimum and maximum). If working with an integer
grid, the VAT can be displayed with LIST to see exactly what
the cell values are as well as their frequency.
The HISTOGRAM Command
Displays the frequency distribution of values in a grid.
Usage: HISTOGRAM {item} {n_levels}
{max_count} {zone_grid}
The DISPLAY device must be defined.
is the grid whose values the frequency will be
displayed for.
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Displaying Grids (Continued)
The HISTOGRAM Command (Continued)
{item} is the item in the VAT the frequency will be displayed
for. A # should be used if the grid is floating point.
{n_levels} is the number of intervals to be used when
reclassifying a floating point grid to integer.
{max_count} is the maximum frequency along the Y axis.
The example below illustrates the output from HISTOGRAM
for a grid called MAP11:
MAPI 1
Remap Tables
Remap tables can also be used to reclassify grid data for display.
A remap table may be either an INFO table or an ASCII file.
A remap table has two parts:
1. A cell value to be reclassed
2. The reclassified value.
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Displaying Grids (Continued)
Remap Tables (Continued)
A remap table for a grid is much like a lookup table is used to
display coverage features.
For integer grids, any numeric item in the VAT may be
remapped. For floating point grids, VALUE must be used since
there are no additional items to reference.
An INFO remap table consists of two items, the VAT numeric
item to remap and the item SYMBOL to store the remapped
symbol. The table must be sorted in ascending order on the VAT
item being reclassed.
When an INFO remap table is used, if a value is not located, the
next highest value in the remap table will be used just like
ranges are handled for lookup tables.
An ASCII remap table consists of comments, optional keywords,
and assignment statements.
Comments are descriptive text strings to describe the remap
table. Comments can appear anywhere and must begin with a
pound sign (#).
Two optional keywords are LOWEST-INPUT and LOWEST-
OUTPUT and must appear above the assignment statements.
LOWEST-VALUE is used to identify the lowest cell
value in the grid to reclassify. LOWEST-OUTPUT is
used to identifies the starting reclass value (if not specified the
default is 1).
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Displaying Grids (Continued)
Remap Tables (Continued)
The assignment statements assign an output value to a specified
input cell value or range of values. The assignment statement
can be defined in several ways. These are:
1. Value alone - The reclass value is determined from the
LOWEST-OUTPUT value (which must be specified). The
first input value is assigned the value of the LOWEST-
OUTPUT value, the second input value is assigned the
value of LOWEST-OUTPUT value + 1, and so on. For
example:
# Example 1 Remap Table
lowest-input 3
lowest-output 2
5
6
7
15
Input values less than 3 are assigned a reclass value of
NODATA. An input value >= 3 and <= 5 are assigned a
reclass value of 2. An input value of > 5 and <= 6 are
assigned a reclass value of 3. An input value of > 6 and
<= 7 are assigned a reclass value of 4. An input value > 7
and <= 15 are assigned a reclass value of 5. All cell values
> 15 are assigned a reclass value of NODATA. If
LOWEST-INPUT were omitted, all cell values less than 5
would have been reclassed as NODATA.
2. Ranges - Explicit ranges are specified. For example:
# Example 2 Remap Table
lowest-output 2
3 5
5 9
13 15
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Displaying Grids (Continued)
Remap Tables (Continued)
Input values less than 3 are assigned a reclass value of
NODATA. Cell values >= 3 and <= 5 are assigned a reclass
value of 2. Cell values > 5 and <= 9 are assigned a reclass
value of 3. Cell values > 9 and <= 13 are assigned
NODATA. Cell values > 13 and <= 15 are assigned a
reclass value of 4. Cell values > 15 are assigned NODATA.
3. User-specified output values - An additional field may be
added to the remap table. The input cell value and range
value are followed by a colon (:) and then the reclass value.
For example:
# Example 3 Remap Table
lowest-input 3
5:10
6:16
7:62
15:28
Input values less than 3 are assigned a reclass value of
NODATA. Cell values >= 3 and <= 5 are assigned a reclass
value of 10. Cell values > 5 and <= 6 are assigned a reclass
value of 16. Cell values > 6 and <= 7 are assigned a value
of 62. Cell values > 7 and <= 15 are assigned a reclass value
of 28. Cell values > 15 are assigned NODATA.
4. Explicit input ranges and user-specified output - Same as
example 3 but input value ranges are specified. For
example:
# Example 4 Remap Table
3 5:9
5 9:8
13 15:59
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Displaying Grids (Continued)
Remap Tables (Continued)
Input values less than 3 are assigned a reclass value of
NODATA. Cell values >= 3 and <= 5 are assigned a reclass
value of 9. Cell values > 5 and <= 9 are assigned a reclass
value of 8. Cell values > 9 and <= 13 are assigned
NODATA. Cell values > 13 and <= 15 are assigned a
reclass value of 59. Cell values > 15 are assigned
NODATA.
Colormap Files
A colormap file is an ASCII file of color index numbers and
their corresponding RGB values.
A colormap file should be in the format:
index_number red green blue
For example:
10 0 0
2 255 0 0
3 0 255 0
4 0 0 255
A colormap file should be sorted in ascending order on the
device index number.
Pseudocolor 8-bit display devices can only display 256 colors at
one time. Pseudocolor devices use a device colormap to
determine which colors will be assigned to pixel values on the
screen. The device colormap contains colorcells that define the
red, green, and blue color components for a given pixel value.
Over 16.7 (256x256x256) colors are possible, but only 256 may be
used at any one time.
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Displaying Grids (Continued)
Colormap Files (Continued)
When ARC/INFO requests a color be drawn on the screen, that
color is loaded into the device colormap.
In order to give the user control over how images and grids are
displayed, the display colormap is divided into static and
dynamic colorcells. Static colorcells are loaded with predefined
colors (n red, n green, and n blue colors). Dynamic colorcells are
temporary colors that are defined and allocated as needed.
By default, ARC/INFO creates a display colormap that contains
only static colorcells. If there are 216 static colorcells (6 levels
of red, 6 levels of green, and 6 levels of blue), there are 6
possible shades of gray. However, the eye can interpret about 20
shades of gray. For this reason, it is often useful to create
dynamic colorcells to enable images and grids to be displayed
with a more varying number of shades.
The DISPLAY COLORMAP
command can be used to specify the total number of colorcells
to allocation and the number of static colorcells. The difference
in the number of static colors and the specified total will be the
number of dynamic colors available.
The COLOR command can be used to redefine color component
values of the specified hardware device index. Its usage is
COLOR . Device indexes 0
through 7 may always be redefined. Otherwise, a device index
greater than 7 should be used to define a dynamic color.
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Displaying Grids (Continued)
GRID Display Commands
The following commands are used to display grids in Arcplot:
The GRIDNODATASYMBOL Command
Sets the shade symbol or colormap index for displaying grid
cells with NODATA values.
Usage: GRIDNODATASYMBOL
Usage: GRIDNODATASYMBOL TRANSPARENT
Usage: GRIDNODATASYMBOL {SPOT }
Usage: GRIDNODATASYMBOL
{SPOT }
is the shade symbol or colormap
index used to display cells with a value of NODATA.
TRANSPARENT denotes that NODATA will be displayed
transparently.
{SPOT } is the colorname and optional spot
percentage to display NODATA cells. Colornames are stored in
stored in $ARCHOME/symbols/colorfile (an ASCII file).
{SPOT } is a color
model, its parameters, and optionally a spot percentage used to
display cells assigned NODATA.
Arcplot and GRID support five color models. These are:
1. HSV - hue saturation value
2. HLS - hue lightness saturation
3. RGB - red green blue
4. CMY - cyan magenta yellow
5. CMYK - cyan magenta yellow black
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Displaying Grids (Continued)
The GRIPPAINT Command
Displays a grid using the specified item value, stretch, or remap
table and a colormap file.
Usage: GRIDPAINT {item}
{IDENTITY I LINEAR I EQUALAREA I remap_table}
{WRAP I NOWRAP} {NOMINAL I GRAY I colormap_file}
is the grid to display.
{item} is an item in the VAT. If no item is specified, the default
is VALUE. The item must be numeric.
{IDENTITY} is the default. It means no stretch is applied and
the cell value will be used as the shade symbol.
{ LINEAR} means a linear stretch will be applied. Values are
stretched from 0 to 255.
{EQUALAREA} means an equal-area stretch will be applied.
Values are stretched from 0 to 255.
{remap_table} means a remap table will be used to determine
the symbol to be used to display each cell value.
{WRAP} means the values in the colormap will be repeated to
fulfill the range of values required by the grid. This is the
default.
{NOWRAP} means the values in the colormap file will not be
repeated. Values outside the colormap range will be displayed
as NOD ATA cells.
{NOMINAL} means that sixteen colors will be used to display
the grid. This is typically used to display integer grids.
{GRAY} means that 256 symbols with values from 0 to 255 will
be used. This is typically used to display floating point grids.
{colormap_file} an ASCII file of index numbers and RGB values
used to display a grid.
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Displaying Grids (Continued)
The GRIDSHADES Command
Shades a grid using the specified item value, stretch, or remap
table to determine color from the current shadeset.
Usage: GRIDSHADES {item}
{IDENTITY I LINEAR I EQUALAREA I remap_table}
{WRAP I NOWRAP}
is the grid to display.
{item} is an item in the VAT. If no item is specified, the default
is VALUE. The item must be numeric.
{IDENTITY} is the default. It means no stretch is applied and
the cell value will be used as the shade symbol.
{ LINEAR} means a linear stretch will be applied. Values are
stretched from 0 to 255.
{EQUALAREA} means an equal-area stretch will be applied.
Values are stretched from 0 to 255.
{remap_table} means a remap table will be used to determine
the symbol to be used to display each cell value.
{WRAP} means the values in the colormap will be repeated to
fulfill the range of values required by the grid. This is the
default.
{NOWRAP} means the values in the colormap file will not be
repeated. Values outside the colormap range will be displayed
as NODATA cells.
The SHADECOLORRAMP command in Arcplot can be used to
create ramps of continuous colors suitable for display of ordinal
and surface data.
Only the color component of the shadeset is used in displaying
the values of a cell.
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Displaying Grids (Continued)
The GRIPCOMPOSITE Command
Displays three grids as a composite image.
Usage: GRIDCOMPOSITE
{IDENTITY I LINEAR I EQUALAREA}
Usage: GRIDCOMPOSITE
{IDENTITY I LINEAR I EQUALAREA}
is the grid to be displayed as red.
is the grid to be displayed as green.
is the grid to be displayed as blue.
{IDENTITY} is the default. It means no stretch is applied and
the cell value will be used as the shade symbol.
{ LINEAR} means a linear stretch will be applied. Values are
stretched from 0 to 255.
{EQUALAREA} means an equal-area stretch will be applied.
Values are stretched from 0 to 255.
is the grid to be displayed as hue.
is the grid to be displayed as saturation.
is the grid to be displayed as value.
GRIDCOMPOSITE can be used for displaying multi-band
images converted to grid.
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Displaying Grids (Continued)
The GRIPDIRECTION Command
Draws arrows whose direction is determined by the value of the
grid cells.
Usage: GRIDDIRECTION {sample_interval}
{NORTH I EAST I SOUTH I WEST}
{CLOCK I COUNTERCLOCK} {reference_value}
{degree_step}
is the grid to be displayed with arrows.
{sample_interval} is the number of cells in the grid's x and y
direction that will be sampled to produce a single arrow, the
nearest neighbor value to the center of the sample will be used
as the direction for the sample. The default is 1.
{NORTH I EAST I SOUTH I WEST} is the direction of the
reference value. The default is NORTH.
{CLOCK I COUNTERCLOCK} is the direction in which to
increment. CLOCK is the default.
{reference_value} is the starting value for the specified direction.
The default is 0.
{degree_step} the step interval for incrementing to the next
direction. The default is 1. This can be determined by dividing
the range of values by 360.
The values for the input grid should represent a continuous
range of direction.
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Displaying Grids (Continued)
The GRIDNET Command
Draws a fishnet or mesh of lines delineating the boundaries of
cells in a grid, or the boundary of a grid.
Usage: GRIDNET {BND I ALL}
is the name of the input grid.
{BND} means the bounding rectangle of the grid is drawn.
{ALL} means the boundaries of each cell are drawn.
Use the Arcplot line symbol commands to control the line
symbol used to draw the mesh.
The IMAGE Command
Draws a raster image or a group of images from an image
catalog.
Usage: IMAGE {band}
Usage: IMAGE cimage I image_catalog> COMPOSITE
Usage: IMAGE TRANSPARENT
Usage: IMAGE TRANSPARENT
Usage: IMAGE cimage I image_catalog> TRANSPARENT
Usage: IMAGE cimage I image_catalog> OPAQUE
cforeground_shadesymbol> cbackground_shadesymbol>
Usage: IMAGE cimage I image_catalog> OPAQUE
cforeground_colorname>
Usage: IMAGE cimage I image_catalog> OPAQUE
cforeground_colormodel> cparameters> cbackground_colormodel>
cparameters>
A grid may be displayed with the IMAGE command.
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Displaying Grids (Continued)
The ARCFLOT SHADECOLORRAMP Command
Creates shade symbols with a specified color range that replace
the existing shade symbols.
Usage: SHADECOLORRAMP
{LINEAR I NONLINEAR}
is the first symbol number that the color ramp
will be assigned. Valid numbers are 1 to 999.
is the total number of symbols to be
included in the color ramp. The number plus
the total number of symbols cannot exceed 500.
is the color used to start the color ramp.
is the color terminating the color ramp.
{LINEAR} means the symbols will be evenly distributed along a
straight line in color space. This is the default.
{NONLINEAR} means the symbol colors will be determined by
using a curve through color space in order to render a more
aesthetic ramp of well defined and saturated colors.
SHADECOLORRAMP uses the current shade symbol to
automatically regenerate shade symbols.
cannot exceed the number of symbols in
the current shadeset.
All symbols created by SHADECOLORRAMP will be set to
SHADETYPE COLOR in order to display solid-fill shades.
SHADESAVE can be used to save the symbols created by
SHADECOLORRAMP. Before issuing SHADECOLORRAMP,
issue SHADEDELETE ALL and SHADESET to
load just the one shadeset file into the Arcplot shade symbol
buffer.
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Displaying Grids (Continued)
The LOADCOLORMAP Command
Loads the colors in an ASCII colormap file into the current
shadeset.
Usage: LOADCOLORMAP
is the name of the input colormap file.
The colormap symbol numbers must ranger from 1 to 999.
The SHADECOLOR of each symbol is set to the RGB value
from the colormap file.
The SHADETYPE for each symbol is set to COLOR.
If a shade does not exist, a corresponding index number will be
used to create that symbol number.
Use SHADEDELETE ALL then SHADESET
before using LOADCOLORMAP to ensure that only symbols in
the current shadeset are those corresponding to records in the
colormap file.
The SAVECOLORMAP Command
Saves the colors corresponding to symbols in the current
shadeset to an ASCII colormap file.
Usage: SAVECOLORMAP
is the output colormap file.
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Displaying Grids (Continued)
The CONVERTREMAF Command
Converts remap tables from INFO tables to ASCII files or from
ASCII files to INFO tables.
Usage: CONVERTREMAP
{TOINFO I TO ASCII} {value_item} {remap_item}
are the input and output remap
tables.
{TOINFO} converts an ASCII remap table to an INFO remap
table.
{TOASCII} converts an INFO remap table to an ASCII remap
table.
{value_item} is an INFO item whose values are remapped. The
default is VALUE.
{remap_item} is an INFO item holding the remapped values.
The default is LINK.
The CREATEREMAP Command
Generates a remap table for a grid.
Usage: CREATEREMAP
{PIECEWISE I EQINTERVAL I EQAREA I RECNO}
{nlevels} {lowest_level} {ASCII I INFO} {in_item} {out_item}
is the input grid.
is the output remap table.
{PIECEWISE} is a graphic method of piecewise linear mapping.
A histogram of data distribution is drawn and can be
manipulated to redistribute the output data values.
{EQINTERVAL} performs an equal interval mapping of the
values in the input grid, stretching the values from 0 to 255.
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Displaying Grids (Continued)
The CREATEREMAP Command (Continued)
{EQAREA} performs an equal area mapping of values in the
input grid, stretching the values from 0 to 255.
{RECNO} input values are mapped to their corresponding record
number in the VAT. must be an integer grid.
{nlevels} is the number of output values. The default for integer
grids is the number of unique values. For a floating point grid,
the default is 256.
{lowest_level} is the lowest output value. The default is 1.
{ASCII} indicates an ASCII remap table is created.
{INFO} indicates an INFO remap table is created.
{in_item} is the name of the input item for an INFO remap table.
{out_item} is the output item for an INFO remap table.
DISPLAY must be set before using the {PIECEWISE} option.
The REMAPGRID Command
A menu-based tool for creating custom remap tables for a grid.
Usage: REMAPGRID {out_remap} {VAT_item}
is the input grid.
{out_remap} is the output remap table. The name can be omitted
and entered in the menu.
{VAT_item} is the name of the item in to remap. The
default is VALUE.
The menu invoked contains buttons which execute additional
menus for creating a remap table using the options in the
CREATEREMAP command.
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Displaying Grids (Continued)
The SHADEGRID Command
A menu-based tool for generating shade sets and remap tables
that can be used to create a custom display of a grid.
Usage: SHADEGRID
SHADEGRID helps the user interactively create the remap
table(s) and shadeset(s) required to display grids.
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Querying Grids
The CELLVALUE Command
Returns the value and value attributes for the cell containing a
specified point.
Usage: CELLVALUE {item...item I NONE}
Usage: CELLVALUE {NONE I ALL}
is the name of the grid to query.
is the name of the stack to query.
indicates the cell location as an x,y coordinate or
interactive if the * option is used.
{item...item} is an optional list of selected items in the VAT to be
listed for the cell. The default is all items in the VAT are
displayed.
{NONE} indicates that only the VALUE item in the VAT will be
listed.
{ALL} indicates the values for all items in the stack will be
displayed for each selected location.
CELLVALUE is comparable to the Arcplot IDENTIFY command
for coverages.
If the grid is floating point, VALUE is listed.
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Querying Grids (Continued)
The GRIDOUERY Command
Displays the set of cells in a grid that satisfies a logical
expression using the current shadeset.
Usage: GRIDQUERY {item}
{IDENTITY I LINEAR I EQUALAREA I remap_table}
{WRAP I NOWRAP}
is the grid to query.
{item} is an item in the VAT. If no item is specified, the default
is VALUE. The item must be numeric. If no remap or stretch is
given, then {item} is used as the shade symbol numbers to shade
the polygons.
{IDENTITY} is the default. It means no stretch is applied and
the cell value will be used as the shade symbol.
{ LINEAR} means a linear stretch will be applied. Values are
stretched from 0 to 255.
{EQUALAREA} means an equal-area stretch will be applied.
Values are stretched from 0 to 255.
{remap_table} means a remap table will be used to determine
the symbol to be used to display each cell value.
{WRAP} means the values in the colormap will be repeated to
fulfill the range of values required by the grid. This is the
default.
{NOWRAP} means the values in the colormap file will not be
repeated. Values outside the colormap range will be displayed
as NODATA cells.
is a logical expression which operates on
VALUE and attributes of . Those cells for which the
expression is true are selected and displayed.
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GRID Terminology
Grid
A grid describes features and characteristics of an area and their
relative position in space.
Cell
The basic spatial unit in a grid. All cells are square (equal size
in the X and Y dimensions.
Row and Column
Cells are arranged in rows and columns which produce a
Cartesian matrix.
Value
Each cell in a grid is assigned a value to identify the
characteristics of a cell.
Zone
Any two or more cells in the same grid which have the same
value are considered to belong to the same zone. A zone may be
connected or disconnected.
Regions
Each group of connected cells in a zone are considered to be a
region.
VAT
Integer or categorical grids usually have a value attribute table
(VAT), an INFO table containing the items VALUE (for each
unique cell value) COUNT (a cell count or frequency for each
cell value record), and optional items that further describe each
cell value.
Name
Every grid has a filename. Filenames may be 12 characters long.
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GRID Spatial Processing Concepts
The type of grid processing depends on the operator or function
used. Grid function types are local, focal, zonal, and global.
Location Determination
GRID stores the origin of a grid and the cell size and map units.
This allows GRID to determine the row-column address using
x- and y-coordinates.
Cell-by-Cell Processing
GRID performs all operators and functions (except zonal and
global functions) on a cell-by-cell basis. An operator or function
begins at the upper-left corner of a grid and moves from left to
right and top to bottom of the grid until all cells have been
processed. As a cell is processed, the result is written to the
corresponding row-column address in the output grid.
Multi-grid Calculations
Most operators and functions either allow or require multiple
grids as input. All operators and functions process all values
between grids.
Operator and Local Function Processing
All operators and local functions perform cell-by-cell
processing.
Neighborhood Processing
Focal functions also use cell-by-cell processing, but consider the
values of cells within a neighborhood to determine the output
cell value.
Neighborhood-notation Processing
Custom neighborhoods can be defined using neighborhood
notation. The notation is in row-column space and is relative to
the current cell being processed. X,Y offset values are used.
Any cells above the current processing cell receives a negative y-
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GRID Spatial Processing Concepts
offset (0,-); below a positive y-offset (0,+); to the right a positive
x-offset (+,0); and to the left a negative x-offset (-,0).
-2,-2
-1,-2
0,-2
1,-2
2,-2
-2,-1
-1,-1
0,-1
1,-1
2,-1
-2,0
-1,0
0,0
1,0
2,0
-2,1
-1,1
0,1
1,1
2,1
-2,2
-1,2
0,2
1,2
2,2
Note: Cell sizes are actually square in a grid!
Zonal Calculations
Cells are processed zone-by-zone based on the shape of a zone.
Calculating Distance and Direction
Distance is calculated from the center of a cell to the center of an
adjacent cell (which is the cell size times 1.412). To calculate the
distance between cells not in the immediate neighborhood, the
Euclidean distance is measured (using Euclidean functions).
Direction is calculated from center to center of disconnected
cells from any resultant direction grid.
Weight-distance Calculations
Cost-path calculations utilize weighted-surface grids (cost
surface or impedance grids). A weighted-surface assigns a value
to each cell that identifies the cost in some cost-measurement
system, to pass through the cell. It is assumed to starting point
and destination is the center of each cell.
Calculating Area
Area calculations are the result of multiplying the area of each
cell (derived by the cell size) and the number of cells in a zone.
The REGIONGROUP must first be used to calculate the area of
regions.
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GRID Spatial Processing Concepts
Surface Calculations
All surface functions are performed on the lattice view of a grid.
Surface calculations are many times interpolations of values
assigned to the center cells and the influence of surrounding
cells.
Aspect and slope are calculated from a cell's relationship to its
immediate neighbors.
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Map Algebra
Map Algebra
Map algebra is used to create new grids.
AML first processes the input on a Grid: command line.
Functions are evaluated and variable substitution performed.
The result is passed to the GRID interpreter. All communication
with the GRID interpreter is done using the map-algebra
language.
The building blocks for the map-algebra language are objects,
actions, and qualifiers.
Objects may be grids, tables, scalars, constants, and numbers,
they either store information or are values.
Commands, operators, and functions perform an action on input
objects.
Qualifiers and parameters control how and where an action is to
take place.
GRID commands are instructions for managing grids and the
environment in which they are analyzed.
GRID operators perform mathematical computations within and
between grids, tables, scalars, and numbers, and between valid
combinations of them.
The set of GRID operators is made up of arithmetic, relational,
accumulative, Boolean, bitwise, logical, and assignment
operators that support both integer and floating point values;
and combinatorial operators which simultaneously overlay
grids and maintain the input attributes.
GRID functions are spatial cartographic modeling tools
designed to analyze and operate on cell-based data.
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Map Algebra (Continued)
Scalars, constants, and numbers are single-value objects, usually
numeric, that can be used in conjunction with an operator or
function to achieve a desired result.
There are three main input types available with the GRID map
algebra. These are:
1. expressions
2. commands
3. conditional and individual cell processing
Map Algebra Expressions
An expression can perform a single task on a grid, number, or
scalar.
A scalar is GRID variable. The Grid: PRINT
command may be used to list the value of a scalar.
Most expressions are constructed with the "=" operator. For
example: Grid: outgrid = gridl + grid2
Operators can be placed in front of or between a grid, scalar, or
number, as in the example above.
Each operator has an assigned precedence value. Parentheses
overrule precedences. The GRID interpreter completes all
operations within parentheses first.
Parentheses can be nested, with the inner-most pair being
evaluated first.
The following table lists each operator by category, gives a
description of the operator, and lists its precedence:
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Map Algebra (Continued)
Operators
Operator
Description of Operator
Precedence
Arithmetic:
-
unary minus
12
MOD
modulus
11
4-
multiplication
11
/
division
11
div
floating point division
11
+
addition
10
-
subtraction
10
Boolean:
A, not
complement of expression
12
&, and
and
3
!, or
or
2
I, xor
exclusive or
2
Relational:
<, It
less than
6
<=, le
less than or equal to
6
>, Rt
greater than
6
>=' Re
greater than or equal to
6
==, eq
equal to
6
A=, ne
not equal to
6
Bitwise:
AA
bitwise complement of expression
12
ป
right shift
7
ซ
left shift
7
&&
bitwise and
5
|i
bitwise or
4
I I
bitwise exclusive or
4
Combinatorial:
cand
and
9
cor
or
8
cxor
exclusive or
8
Logical:
diff
logical difference
8
in
contained in
8
over
over
8
Accumulative:
+=
adds and assigns value to
1
-+
subtracts and assigns value to
1
multiplies and assigns value to
1
/+
divides and assigns value to
1
(=
identifies minimum and assigns value to
1
}=
identifies maximum and assigns value to
1
Assignment:
=
create a new grid
1
:=
assign value to a temporary variable
1
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Map Algebra (Continued)
Expressions executing functions are dependent upon the syntax
and parameters associated with each function.
Functions have the same precedence and are simply executed
from left to right.
Functions can be nested. The inner-most function is executed
first, and its output is used as input for the surrounding
function. For example:
Grid: tempxx8 = con(isnull(tempxx7),0,taipxx7)
The ISNULLO function is executed first, followed by CON().
GRID Commands
GRID commands are similar to simple expressions, but they do
not use an assignment operator.
GRID commands complete a single task or sets a parameter that
will be used in future processing (i.e. SETCELL,
CREATEREMAP, etc.).
Map-algebra Input Types
Valid input types are grids, tables, scalars, constants, and
numbers.
All grids, tables, and scalars used on the right side of an
assignment must exist prior to processing the expression.
Map-algebra Results
All functions and operators either return a grid, table, or scalar.
A VAT will usually be created for a resulting integer grid. The
VAT will contain the items VALUE and COUNT.
Combinatorial operators used on two grids creates a new
composite grid.
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Map Algebra (Continued)
Multiple Outputs
Most functions generate a single new grid, table, or scalar, but
some create multiple grids. Examples are the Euclidean
allocation and cost allocation functions.
NOD ATA in GRID
NODATA is fully supported by GRID. A cell is assigned
NOD ATA when there is inadequate information about the cell
location for a theme.
The three ways NODATA can be treated in a computation are:
1. Return NODATA for the location no matter what
2. Ignore the NODATA and compute with available values
3. Estimate what the value can be
The behavior of NODATA is discussed in ArcDOC for each
GRID function and operator.
For any operator or local function, if any cell in any of the input
grids are assigned NODATA, the output of the cell location will
be NODATA. This cannot be overridden.
For focal functions, if any cell location in a neighborhood of a
processing cell is assigned NODATA, the function will ignore
the NODATA value and compute with the remaining values.
The NODATA keyword can be used to force the processing cell
to be assigned NODATA if any cell in the neighborhood has a
value of NODATA.
For zonal functions, if any cell location on the input value grid
in a zone defined by the input zone grid is assigned NODATA,
the default is the function will ignore the NODATA value and
compute with the remaining values.
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Map Algebra (Continued)
For Euclidean global functions, the NOD ATA value is ignored
for computations since the distance and direction are true
Euclidean distance and direction.
For cost global functions, any cell assigned NODATA in the per-
cell cost grid will be considered a barrier in computations, and
the cell locations containing NODATA values on the input
weight grid will contain NODATA on the output.
For the remaining global functions, when NODATA exists at
any location on the input grid, the output value for that location
will receive NODATA.
With the SELECT function, when the results of the evaluation of
the conditions are not true in the expression, NODATA is
returned rather than 0.
The TEST function returns 0 when the expression is false and 1
when the expression is true.
Direct Display of Analysis Results
It may sometimes be desirable to display the results of a map-
algebra expression rather than creating an output grid (such as
experimenting with new functionality). This can be
accomplished by using the $$display symbolic name for the
output argument in a map-algebra expression. For example:
Grid: $$display = float(gridl6)
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Miscellaneous Functions
The following functions provide functionality necessary for
GRID operations, but not necessarily pertinent to any single
GRID application:
The ABS Function
Calculates the absolute value of the input.
ABS ()
Input values can be integer or floating point. If the input values
are integer, the output values will be integer. And if the input
values are floating point, the output values will be floating
point.
Input values can be negative or positive.
The absolute value may be calculated on an input grid, scalar, or
number.
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The CEIL Function
Returns the next highest whole value that is greater than or
equal to the input values.
CEIL ()
Input values can be negative or positive.
If the input value has values to the right of the decimal, the
output will be assigned the next highest whole value. For
example:
Input Output
1.1 2.0
1.0 1.0
-0.5 0.0
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The CON Function
Performs one or more conditional if/else evaluations.
CON(, /
{, }, ...
{ , }, {false_expression})
is any valid Boolean or relational expression
involving multiple grids, scalars, numbers, or expressions.
is true.
Multiple , statements may be
specified.
{false_expression} is the value to be assigned if none of the
statement are true.
If the any arguments or the
{false_expressionj argument contains floating point values, the
output grid will be floating point.
The CON functions allows the use of any grid function and the
embedding of functions.
If the evaluates to a non-zero number, the condition
is considered true.
If no {false_expression} is supplied, NODATA is assigned to
those cells where all arguments evaluated false.
In the example statement below:
Grid: tempxx8 = con(isnull(tempxx7),0,tempxx7)
If the input cell value in tempxx7 is NODATA, the ISNULL
function assigns a value of 1. Since 1 is non-zero, the condition
is considered true and CON assigns 0 to the cell. Otherwise, the
original cell value is used as the output cell value. In this
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The CON Function (Continued)
manner, NOD ATA cell values can be converted to 0 (which is
required when a function will not operate as desired on
NOD ATA cell values.
In the next example:
Grid: tempxx8 = con(tempxx7 == 0, 99,tempxx7)
If the input cell value in tempxx7 is 99 (using the == relational
operator), the CON function assigns a value of 0. Otherwise, the
original cell value is used as the output cell value.
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The FLOAT Function
Converts integer values to floating point values.
FLOAT ()
Input values can be negative or positive.
If floating point values are input, the output will be the same as
the input.
An integer value of 1 would be converted to 1.0.
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The FLOOR Function
Returns the greatest integer value that is smaller than or equal to
the input values.
FLOOR ()
Input values can be negative or positive.
If the input value has values to the right of the decimal, the output
will be assigned the next lowest whole value.
For example, an input of 1.0 returns 1.0, an input of 1.1 returns
1.0, and an input of -0.2 returns -1.0.
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The FMOD Function
Divides the values of the first input by the second input and
returns the remainder on a cell-by-cell basis.
FMOD (, )
The output values are always floating point regardless of the
input values.
A value divided by 0 is assigned NOD ATA.
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The INT Function
Converts input floating point values to integer values through
truncation.
INT ()
Input values should be floating point and can be either positive
or negative.
If rounding is preferred rather than truncating, add 0.5 to the
expression (outgrid = int(ingrid + 0.5)
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The ISNULL Function
Returns "1" if input value is NOD ATA, and "0" if it is not.
ISNULL ()
Input values can be positive or negative.
The output value types are always integer. The values are either
0 or 1.
In the example statement below:
Grid: tempxx8 = con(isnull(tempxx7),0,tempxx7)
If the input cell value in tempxx7 is NOD ATA, the ISNULL
function assigns a value of 1. Since 1 is non-zero, the condition
is considered true and CON assigns 0 to the cell. Otherwise, the
original cell value is used as the output cell value. In this
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The MERGE Function
Merges multiple, possibly non-adjacent input grids into a single
grid based on order of input.
MERGE (...)
If any input grid is floating point, the output will be floating
point.
If the input grids do not have the same extent, the output grid
will be assigned a boundary as the minimum bounding
rectangle of all inputs.
A maximum of 50 grids may be opened at one time. This allows
49 inputs to be specified and 1 output grid.
If floating point grids have difference cell sizes, RESAMPLEO
may be used to resample the data using BILINEAR interpolation
or CUBIC convolution. Otherwise, MERGE uses the NEAREST
neighbor method for resampling the cell sizes and determining
output cell values.
Input grids may be adjacent, entirely overlapping, partially
overlapping, or entirely separated.
Output cell values are assigned based on the first value at each
cell location that is not NODATA, based on the order the grid
arguments are specified.
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The MOSAIC Function
Merges multiple adjacent continuous grids and performs
interpolation in the overlapping areas.
MOSAIC (...)
MOSAIC is designed primarily for continuous data. It can
minimize the abrupt changes along the boundaries of
overlapping grids. Examples are satellite images, DEMs, etc.
The output grid will be a floating point grid unless all inputs
are integer.
A maximum of 50 grids may be opened at one time. This allows
49 inputs to be specified and 1 output grid.
If floating point grids have difference cell sizes, RESAMPLEO
may be used to resample the data using BILINEAR interpolation
or CUBIC convolution. Otherwise, MERGE uses the NEAREST
neighbor method for resampling the cell sizes and determining
output cell values.
The order the grids are listed as arguments has not impact on
the output cell values assigned. Output cell values are
determined by a weighted average method for overlap areas.
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The NORMAL Function
Creates a grid with randomly dispersed values of a normal
distribution.
NORMAL ()
There are no arguments for the NORMAL function. The output
is a grid of the same extent and cell size as the current analysis
window. SETWINDOW and SETCELL must be specified before
using NORMAL.
The output grid is always floating point.
By default, the NORMAL function sets a mean to 0 and a
standard deviation to 1. These can be changed by the user. For a
mean of 50 and s standard deviation of 3.2, the expression would
be:
Grid: outgrid = normal() * 3.2 + 50
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The PICK Function
Using the values of an input grid, determines which expression
will be used to compute output values.
PICK (, ,...,)
is an input integer or floating point grid, or an
expression resulting in a grid.
,..., is any valid map-algebra
expression or a single grid, number, or scalar. If the value in
equals 1, then the first expression in the expression list is
used to compute the output cell value. If the value in the input
grid equals 2, the second expression will be used, and so on.
Any NOD ATA value on the input grid will receive NOD ATA
on the output grid.
If there is not an expression corresponding to the cell value, the
cell is assigned NOD ATA.
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The RAND Function
Generates a random number between "0" and "1".
RANDO
There are no arguments with the RAND function. The output is
a grid of the same size as the current analysis window, or a
scalar. SETWINDOW and SETCELL must be set before using
RANDO.
The output values are always floating point.
A linear stretch is needed to display values less that 1.0.
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The SAMPLE Function
Lists the values of a group of cells from one or more grids.
SAMPLE (, {grid...grid})
SAMPLE (* I point_file>, {gridgrid},
{NEAREST I BILINEAR I CUBIC})
defines the cells to sample. Cells in mask grid
with value values will be sampled.
{grid...grid} is the name of one or more grids whose values will
be sampled based upon
<*> allows interactive specification of input points.
is an ASCII text file containing coordinate points to
be sampled.
{NEAREST I BILINEAR I CUBIC} specifies the resampling
algorithm to use when sampling a grid. It is used only when
point coordinates are entered as input.
If the cell in the sample {grid...grid} is NOD AT A, its values will
be listed in the output file as missing.
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The SAMPLE Function (Continued)
If no grid is specified, the output will be zone#, x and y
coordinates of the cells in or points specified by
<*> or in .
An output will be created (outfile = sample (arguments)).
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The SETNULL Function
returns NOD ATA if the evaluation of the input condition is
true; if it is false, returns the value specified by the second input
argument.
SETNULL (, {grid I scalar I number})
can be a relational expression or a single grid,
scalar, or number, or expression resulting in a single grid, scalar,
or number.
{grid I scalar I number} determines what the output value will
be if the evaluation condition is false.
Input values can be positive or negative.
If the input value is a single value greater than 0, the output will
be NODATA at all cell locations (output = setnull(3, ingridl))
SETNULL is useful for changing values that meet a certain
condition to NODATA. This can be used to remove certain cells
from further processing.
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GRID Functions
Individual Cell Processing
The DOCELL block and neighborhood notation are two
facilities within the GRID map-algebra language that allow the
development of custom functions and the creation of application
models.
The DOCELL Block
The DOCELL block provides the capability to control
processing on a cell-by-cell basis with conditional statements,
built-in procedures, and access to variables associated with a
grid.
A block begins with the word DOCELL and ends with the word
END.
A DOCELL block is comparable to a GRID function. However,
it can as many statements and expressions as desired.
A DOCELL block can accept multiple grids, scalars, and
combination of grids and scalars. Integer and floating point
values are acceptable.
A DOCELL block may be executed from an AML file (executed
with the &RUN directive) or from the Grid: prompt.
Temporary grids may be created in a DOCELL block using the
temporary assignment operator
The use of neighborhood notation is supported within a
DOCELL block.
The IF and WHILE statements may be used within a DOCELL
block.
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The IF Statement
Performs a conditional if/else evaluation on a cell-by-cell basis
within the analysis window.
IF () {ENDIF}
IF ()
{ELSE IF } {ELSE }
{ENDIF}
is any valid Boolean or relational expression
involving multiple grids, scalars, or numbers.
is the statement of expression that will be used
to compute the output value if evaluates true.
{ENDIF} is an optional keyword used to signal the end of input
for an IF statement. An IF statement will not be processed until
an ENDIF or a statement outside the scope of the IF is executed.
ELSE IF allows for an else clause. IF the IF condition is false,
the ELSE IF clause is evaluated.
ฎ ELSE is the statement list evaluated when a
prior condition evaluates false.
Example:
Grid: if (ingrid > 5) outgrid = 100
:: else outgrid = 0
:: endif
If no ELSE is specified, NOD ATA is assigned to cells evaluating
to false for
If multiple statements are included in , the
block must begin with the keyword BEGIN or the character "{".
The block must end with the keyword END or the character
For example:
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The IF Statement (Continued)
outval = scalar(O)
DOCELL
if (ingrid > 5)
begin
outval = outval + 1
outgrid = 100 * outval
end
END
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The WHILE Statement
Repeats a statement list body as long as the tested condition is a
semi-Boolean true value (non-zero) on a cell-by-cell basis in the
analysis window.
WHILE ()
is any valid Boolean or relational expression
involving single or multiple grids, scalars, or numbers.
is one or more assignment expressions of other
valid statement used to compute the output value as long as
is true.
If multiple statements are included in , the
block must begin with the keyword BEGIN or the character
The block must end with the keyword END or the character
For example:
DOCELL
var:= 10
outgrid = ingridl
while (var > 0)
begin
outgrid = ingrid + outgrid
var := var -1
end
END
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The SCALAR Function
Returns the result of a map algebra expression involving
numbers as a numeric value that can be assigned to a scalar
variable.
SCALAR ()
The output type is the type of the input value.
A permanent scalar variable is created. The REMOVESCALAR
command can be used to remove a scalar variable.
If SCALAR is used outside a DOCELL block, the variable will
be set as a global, and is accessible from within a DOCELL
block.
If SCALAR is used within a DOCELL block, the variable can be
accessed with the AML show function [SHOW
].
Numbers, both integer and floating point, are the only valid
inputs.
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The := Operator
Creates a temporary output grid from an input grid, scalar,
number, or expression on a cell-by-cell basis within a DOCELL
block.
:=
is the temporary output grid.
is the object operated on.
:= can only be used in a DOCELL block.
The size of the output grid is the size of the analysis window.
The assignment operators and produce the same
results. However, := does not write the results to disk but saves
them in memory.
The SCALAR function can be used to force the output to be a
scalar and not a grid (out := scalar(5+3))
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Trigonometric Functions
The following table indicates the trigonometric functions within
GRID, a description of their use, and their usage:
Function
Description
Usage
ACOS
Calculates the inverse cosine of the
input
ACOS()
ACOSH
Calculates the inverse hyperbolic
cosine of the input
ACOSH()
ASIN
Calculates the inverse sine of the
input
ASIN()
ASINH
Calculates the inverse hyperbolic sine
of the input
ASINH()
ATAN
Calculates the inverse tangent of the
input
ATAN()
ATAN2
Calculates the inverse tangent (based
on y/x) of the input
ATAN2(,
ATAN2()
ATANH
Calculates the inverse hyperbolic
tangent of the input
ATANH()
COS
Calculates the cosine of the input
COS()
COSH
Calculates the hyperbolic cosine of the
input
COSH()
SIN
Calculates the sine of the input
SIN()
SINH
Calculates the hyperbolic sine of the
input
SINH()
TAN
Calculates the tangent of the input
TAN()
TANH
Calculates the hyperbolic tangent of
the input
TANH()
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Logarithmic and Exponential Functions
The following table indicates the logarithmic and exponential
functions within GRID, a description of their use, and their
usage:
Function
Description
Usage
EXP
Calculates the base e exponential of
the input
EXP()
EXP10
Calculates the base 10 exponential of
the input
EXP10()
EXP2
Calculates the base 2 exponential of
the input
EXP2()
LN
Calculates the natural logarithm of
the input
LN()
LOGIO
Calculates the base 10 logarithm of
the input
LOG10()
LOG2
Calculates the base 2 logarithm of the
input
LOG2()
POW
Calculates the nth power of the input
POW(, )
SQR
Calculates the square of the input
SQR()
SQRT
Calculates the square root of the input
SQRT()
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Statistical Functions
The following table indicates the logarithmic and exponential
functions within GRID, a description of their use, and their
usage:
Function
Description
Usage
EQUALTO
Evaluates, on a cell-by-cell
basis, the number of times in
an argument list that the
input grid values are equal
to the value specified by the
first argument.
EQUALTO(,
)
GREATERTHAN
Evaluates, on a cell-by-cell
basis, the number of times in
an argument list that the
input grid values are greater
than the value specified by
the first argument.
GREATERTHAN(,
)
LESSTHAN
Evaluates, on a cell-by-cell
basis, the number of times in
an argument list that the
input grid values are less
than the value specified by
the first argument.
LESSTHAN(,
)
LPOS
Determines, on a cell-by-cell
basis, the position of the
input grid with the
minimum value in the
argument list.
LPOS()
MAJORITY
Uses multiple input grids to
determine the majority value
(the value that appears most
often) on a cell by cell basis.
MAJORITY()
MAX
Uses multiple input grids to
determine the maximum
value on a cell-by-cell basis.
MAX()
MEAN
Uses multiple input grids to
determine the mean value
on a cell-by-cell basis.
MEAN()
MED
Uses multiple input grids to
determine the median value
on a cell-by-cell basis.
MED()
MIN
Uses multiple input grids to
determine the minimum
value on a cell-by-cell basis.
MIN()
MINORITY
Uses multiple input grids to
determine the minority
value on a cell-by-cell basis.
MINORITY()
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Statistical Functions (Continued)
Function
Description
Usage
MLCLASSIFY
Performs maximum
likelihood classification on a
stack and creates the
classification grid.
MLCLASSIFY(, ,
(reject_fraction). (EQUAL I SAMPLES
I FILEj, (o_priori_file|, {o_reject_grid})
POPULARITY
Determines the value in an
argument list that is at a
certain level of popularity on
a cell-by-cell basis.
POPULARITY(,
)
RANK
Returns the value in the nth
rank order of the argument
list.
RANK(,
)
UPOS
Determines, on a cell-by-cell
basis, the position of the
input grid with the
minimum value in the
argument list.
UPOS()
VARIETY
Uses multiple input grids to
determine the variety of
values on a cell-by-cell basis.
VARIETY()
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Selection Functions
The following section presents some descriptions of selection
functions:
The SELECT Function
Based on the evaluation of the , selects cell
values from the input grid on a cell-by-cell basis within the
analysis window.
SELECT(/ , {o_value_item})
is the input grid the selection is performed upon.
is a logical INFO selection which operates
on VALUE and other attributes of a 's VAT. Those cells
which evaluate true are selected and written to the output grid.
Those cells that are not selected are set to NOD ATA.
If the input grid is floating point, VALUE is used for the
selection, and the output grid will be floating point.
{o_value_item} is an alternate item in a VAT (used only if
is integer) used as the VALUE in the output grid. If no
{o_value_item} is given, the input grid VALUE is written to the
output grid.
The general form of a logical expression is:
The logical expression must be contained within single quotes.
For example:
Grid: outgrid = select(ingrid, 'value > 100')
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The SELECT Function (Continued)
If the logical expression contains a character string, it must be
doubled quoted. For example:
Grid: outgrid = select(ingrid, 'name cn ''test'")
Valid logical expression operators are:
EQ
=
NE
<>
GE
>=
LE
<=
LT
<
GT
>
CN
NC
IN
LK
Valid logical expression connectors are: AND, OR and XOR.
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The SELECTBOX Function
Selects cells from the input grid that are either inside or outside
a specified box within the analysis window.
SELECTBOX(, ,
{INSIDE I OUTSIDE})
SELECTBOX(, <*>, {INSIDE I OUTSIDE})
is the input grid the selection is performed upon.
allows the box to be specified in map
units.
{INSIDE} indicates the cells inside the box will be selected. All
cells outside will receive NOD AT A.
{OUTSIDE} indicates the cells outside the box will be selected.
All cells inside will receive NODATA.
<*> means the box is defined interactively.
An alternate item in the VAT can be specified using the syntax
.- . For example:
output = selectbox(ingrid.item, *)
The center of a cell is used to determine whether a cell is inside
or outside the box.
When the is used, the grid does not
have to be displayed on the screen.
When <*> is used, the grid should be displayed on the screen.
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The SELECTCIRCLE Function
Selects cells from the input grid that are either inside or outside
a specified circle within the analysis window.
SELECTCIRCLE(, , {INSIDE I OUTSIDE})
SELECTCIRCLE(, <*, r>, {INSIDE I OUTSIDE})
SELECTCIRCLE(/ <*>, {INSIDE I OUTSIDE})
is the input grid the selection is performed upon.
allows the center of the circle and the radius to be
specified in map units.
<*, r> allows the center of the circle to be specified interactively
and the radius given explicitly.
<*> allows the center of the circle and the radius to be specified
interactively.
{INSIDE} indicates the cells inside the circle will be selected.
All cells outside will receive NODATA.
{OUTSIDE} indicates the cells outside the circle will be selected.
All cells inside will receive NODATA.
An alternate item in the VAT can be specified using the syntax
.- . For example:
output = selectcircle(ingrid.item, *)
The center of a cell is used to determine whether a cell is inside
or outside the box.
When <*> is used, the grid should be displayed on the screen.
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The TEST Function
Uses a Boolean evaluation of the to test the
cell values from the input grid and to set the output to "1" or "0"
on a cell-by-cell basis within the analysis window.
TEST(, )
is the input grid the test is performed upon.
is a logical INFO selection which operates
on VALUE and other attributes of a /s VAT. Those cells
which evaluate true are assigned 1 in the output grid. Those
cells that are not selected are set to 0.
If the input grid is floating point, VALUE is used for the
selection, and the output grid will be floating point.
The general form of a logical expression is:
The logical expression must be contained within single quotes.
For example:
Grid: outgrid = test(ingrid, 'value > 100')
If the logical expression contains a character string, it must be
doubled quoted. For example:
Grid: outgrid = test(ingrid, 'name cn "test"')
Valid logical expression operators are:
EQ
=
NE
<>
GE
>=
LE
<=
LT
<
GT
>
CN
NC
IN
LK
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Reclassification Functions
The following section presents some descriptions of
reclassification functions:
The RECLASS Function
Reclassifies (or changes) the value of input cells using a remap
table on a cell-by-cell basis within the analysis window.
RECLASS(/ / {DATA I NODATA},
{in_item}, {out_item})
is the input grid to reclassify.
is an INFO or ASCII remap table.
{DATA} indicates that if the input value is not present in the
, the value should remain intact for that location
on the output grid.
{NODATA} indicates that if the input value is not present in the
, the value should be assigned NOD ATA for that
location on the output grid.
{in_item} specifies the item in an INFO remap table that is to be
used to correlate the values on the input grid that will be
reclassed.
{out_item} is the item in an INFO remap table that is to be used
to change or reclass the input values to the values contained in
{out_item}.
The output grid will always be integer type. If the output
values in the remap table are floating point, they are truncated
before the reclass.
Any value in the VAT can be used for the reclass. For example:
Grid: outgrid = reclass(ingrid.ph, ph.rmt)
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The RECLASS Function (Continued)
If a mask is set, the cell locations masked out will be assigned
NODATA.
The input grid must have a valid .STA file created with the
GRID BUILDSTA command.
RECLASS assigns input values not explicitly listed in the remap
table as either NODATA or an output value identical to the
input value, depending on the option specified.
Ranges can be specified in an ASCII remap table only. INFO
remap tables are explicit, with ranges not be interpolated as
with display remap tables.
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The SLICE Function
Slices (or changes) a range of values of the input cells by
specified ranges, zones of equal area, or zones with equal
intervals within the analysis window.
SLICE(/ TABLE, , {in_item}, {out_item},
{in_min})
SLICE(, EQAREA, {nzones}, {base_zone#}, {in_min},
{in_max}
SLICE(, EQINTERVAL, {nzones}, {base_zone#}, {in_min},
{in_min})
is the input grid to be sliced.
TABLE indicates a remap table will be used in the slicing
process.
is an ASCII or INFO remap table specifying
which values are to be changed and to what output values.
{in_item} is the input item in an INFO remap table.
{out_item} is the output item in an INFO remap table.
{in_min} is a number that identifies the minimum value from
the input grid for slicing.
EQAREA indicates that the input values will be divided into the
number of zones specified by {nzones} with each zone having a
similar number of cells (each zone represents a similar amount
of area).
{nzones} defines the number of zones that will be used with the
calculation of equal area. The output grid will have (nzones}
with similar numbers of cells.
{base_zone#} is an integer that defines the lowest zone value on
the output grid.
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The SLICE Function (Continued)
{in_min} is a number that identifies cells with values below
{in_min} should be assigned NODATA.
{in_max} is a number that identifies cells greater than {in_max}
should be assigned NODATA.
EQINTERVAL indicates the slice is determined by the range of
the input values and then divides the ranges into {nzones}. Each
zone on a sliced output grid has the potential of having input
cell values that have the same range from the extremes.
{nzones} defines the number of zones that will be used with the
calculation of equal area. The output grid will have (nzones}
each containing equal value ranges on the output grid.
{base_zone#} is an integer that defines the lowest zone value on
the output grid.
{in_min} is a number that identifies cells with values below
{in_min} should be assigned NODATA.
{in_max} is a number that identifies cells greater than {in_max}
should be assigned NODATA.
INFO remap tables can have more than two items (as in display
remap tables) and these items can be used as input and output
remap items.
The result of using an ASCII remap table is the same for SLICE
as it is for display.
Any value in the VAT can be used for the slice example:
Grid: outgrid = slice(ingrid.ph, ph.rmt)
If a mask is set, the cell locations masked out will be assigned
NODATA.
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Shape Analysis Functions
The following section presents some descriptions of shape
analysis functions:
The EXPAND Function
Expands the selected zones by a specified number of cells.
EXPAND(, , LIST, )
EXPAND(, , FILE, )
EXPAND(, , TABLE, , {item})
is the input grid to expand.
are the number of cells to expand each selected zone.
LIST indicates the zones to be selected will be listed on the
command line as .
is the list of zones to be selected up to a maximum
of 20 values.
FILE indicates the list of zones to be selected will be listed in an
ASCII text file. An explicit zone should be listed on a single
line, and ranges should be listed be listed together, space
delimited on the same line.
is an ASCII text file containing the zones to select.
An explicit zone should be listed on a single line, and ranges
should be listed be listed together, space delimited on the same
line. The file must be sorted in ascending order.
TABLE indicates the zones to be selected are listed as single
values in an INFO table.
is the INFO table containing the values to select.
The table should contain the item VALUE or an optional item
specified as {item}.
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The EXPAND Function (Continued)
The expansion occurs in all directions.
When two foreground zones expand into the same background
zone, the conflict is resolved based on the value of the majority
of surrounding cells.
NOD ATA cells are always considered as background cells, and
neighboring cells can expand into NODATA cells. NODATA
cells will never expand into their neighbors.
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The REGIONGROUP Function
Records for each cell in the output the identity of the connected
region to which it belongs within the analysis window. A
unique number is assigned to each region.
REGIONGROUP(/ {o_remap_table}, {FOUR I EIGHT},
{WITHIN I CROSS}, {excluded_value},
{LINK I NOLINK})
Any two cells with the same value are considered a zone.
A region is each group of connected cells within a zone.
is the input grid whose regions will be grouped.
{o_remap_table} is the name of the resulting remap table that
identifies the input value or values from the original grid that
were used to create the output zone.
{FOUR} defines connectivity as being the cells to the right, left,
top, and bottom of the cell being processed.
{EIGHT} defines connectivity as the eight neighborhood cells
surrounding the processing cell.
{WITHIN} will test for connectivity between input values that
are within the same zone. The only cells that can be grouped are
in the same zone.
{CROSS} will test for connectivity by the spatial requirements of
the FOUR and EIGHT keywords between cells with any values
except for cells with a value of {excluded_value}.
{excluded_value} must be specified.
{excluded_value} identifies a value such that if a cell location
contains the value, no connectivity will be evaluated no matter
which keyword is used.
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The REGIONGROUP Function (Continued)
{LINK} means an item LINK will be added to the VAT of the
output grid to hold the original values for each newly created
cell.
{NOLINK} means the VAT will contain only the VALUE and
COUNT items.
The output grid will always be integer.
The input values to be regrouped using any VAT item using the
syntax .- .
REGIONGROUP is useful when analysis must be completed on
regions, not zones.
Cell locations that are excluded values are assigned 0 so that
they are not confused with NOD ATA cells.
If a mask is set, those cells that have been masked out will be
assigned NODATA.
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The SHRINK Function
Shrinks the selected zones by a specified number of cells.
SHRINK(, / LIST, )
SHRINK(, , FILE, )
SHRINK(, , TABLE, , {item})
is the input grid to expand.
are the number of cells to shrink each selected zone.
LIST indicates the zones to be selected will be listed on the
command line as .
is the list of zones to be selected up to a maximum
of 20 values.
FILE indicates the list of zones to be selected will be listed in an
ASCII text file. An explicit zone should be listed on a single
line, and ranges should be listed be listed together, space
delimited on the same line.
is an ASCII text file containing the zones to select.
An explicit zone should be listed on a single line, and ranges
should be listed be listed together, space delimited on the same
line. The file must be sorted in ascending order.
TABLE indicates the zones to be selected are listed as single
values in an INFO table.
is the INFO table containing the values to select.
The table should contain the item VALUE or an optional item
specified as {item}.
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The SHRINK Function (Continued)
The shrinkage occurs in all directions.
When two adjacent regions are part of the selected set to
SHRINK, there is no change in the boundary between them.
NODATA has the same priority as any value to invade areas
vacated by SHRINK. Therefore, if a selected value is adjacent to
NODATA, it may become NODATA following SHRINK.
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Data Cleanup Functions
The following section presents some descriptions of data
cleanup functions:
The BOUNDARYCLEAN Function
Smoothes the boundary between zones by expanding and
shrinking the boundary.
BOUNDARYCLEAN(, {NOSORT I DESCEND I ASCEND},
{TWOWAY I ONEWAY})
is the input integer grid.
{NOSORT} does no sorting by size. This is the default. Zones
with larger values have a higher priority to expand into zones
with smaller values.
{DESCEND} sorts zones in descending order by size.
{ASCEND} sorts zones in ascending order by size.
{TWOWAY} performs expansion and shrinking according to
sorting type, then does an additional shrinking and expansion
with the priority reversed. This is the default.
{ONEWAY} performs expansion and shrinking only once,
according to the sorting type.
All regions of less than 3 cells in the x or y direction will be
changed.
Expansion is identical in the first and second pass.
In the ONEWAY or first pass of the TWOWAY option,
NODATA cells have lowest priority. NODATA cells have the
highest priority in the second pass of the TWOWAY option.
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The BOUNDARYCLEAN Function (Continued)
The shrinking of the ONEWAY option and the first pass of the
TWOWAY option are different than the second pass of the
TWOWAY option. In the first pass, for any processing cell in
the expanded grid which has a neighbor of the original value of
the processing cell, the original value of the processing cell will
be recovered. In the second pass of the TWOWAY option, any
cell in the expanded grid which is not surrounded completely by
eight cells of the same value will recover its original value.
BOUNDARYCLEAN is primarily used for cleaning ragged
edges between zones. It uses an expand then shrink method
which cleans boundaries on a relatively large scale.
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The MATORITYFILTER Function
Replaces cells in grid based on the majority of their contiguous
neighboring cells.
MAJORITYFILTER(, {FOUR I EIGHT),
{MAJORITY I HALF})
is the input integer grid.
ฎ {FOUR} means the kernel of the will be the four direct
neighbors (left, right, top, bottom) to the process cell. This is the
default.
{EIGHT} means the kernel of the will be the eight nearest
neighbors (a 3x3 window) to the present cell.
{MAJORITY} means a majority of the cells must have the same
value and be orthogonally connected (left, right, top, bottom).
Three out of four or five of the eight must have the same value.
This is the default.
{HALF} means half the cells must have the same value and be
orthogonally connected. Two out of four or four out of eight
connected cells must have the same value. Half will have more
of a smoothing effect.
The MAJORITYFILTER has two criteria which must be satisfied
before replacement can occur. These are:
1. The number of neighboring cells of a similar value must
be large enough, MAJORITY or HALF.
2. Those cells must be contiguous about the center of the
filter kernel.
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The NIBBLE Function
Replaces areas in a grid corresponding to a mask with the values
of the nearest neighbor.
NIBBLE(, , {ALL I DATAONLY})
is the input integer grid.
is the name of the integer grid to be used as the
mask. Cells with NODATA as their value will be nibbled.
{ALL} is a keyword that specifies that the nearest neighbor value
will be used whether it is NODATA or another data value in the
grid. NODATA values are free to nibble into areas defined in
the if they are the nearest neighbor.
{DATAONLY} is a keyword that specifies that only data values
are free to nibble into areas defined in the .
NODATA values in the input grid are not allowed to nibble into
areas defined in the even if they are the nearest
neighbor.
NIBBLE allows selected areas of a grid to be assigned the value
of their nearest neighbor. This is useful for editing areas of a
grid known to be erroneous.
NIBBLE determines all areas in the with the value
NODATA. The corresponding areas in the input grid will be
nibbled. Second, the internal Euclidean allocation is performed
to allocate values to the masked cells based on the Euclidean
distance. The value of the cells in the input grid which
correspond to the cells of NODATA are then nibbled away and
replaced by the value of the nearest neighbor according to
Euclidean distance.
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The THIN Function
Thins raster linear features in a grid.
THIN(, {POSITIVE I DATA}, {NOFILTER I FILTER},
{ROUND I SHARP}, {thickness})
is the grid to be thinned.
{POSITIVE} means all cells whose VALUE is greater than 0
belong to the foreground cells; all others are background cells.
{DATA} means all cells whose VALUE are not NODATA are
foreground cells, and NODATA cells are background cells.
{NOFILTER} means no filter will be applied.
{FILTER} means the grid will be filtered to smooth the
boundaries between foreground and background cells. This
option will eliminate minor irregularities from the output grid.
{ROUND} attempts to smooth corners and junctions and is best
for vectorizing natural features such as streams or contours.
{SHARP} attempts to preserve rectangular corners and junctions.
This is best for vectorinzing man-made features such as streets.
{thickness} is the maximum thickness, in map units, of linear
features in the input grid. The default is 10 times the cell size.
Best results are obtained when the {thickness} fits the thickest
linear feature to be thinned.
The thinning process is built into the GRIDLINE and
STREAMLINE functions, thus eliminating the need to thin a
grid before these functions are used.
The FILTER options uses the algorithm from the
BOUNDARYCLEAN command to remove short linear features
extending from the major branch. It may also remove features
narrower than three cells.
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Projecting Grids
Just as it is often necessary to change the map projection of a
coverage, grids must sometimes be projected since all grids
being using for raster analysis must be in the same map
projection. The PROJECT function is provided for this purpose.
Also, the ARC PROJECT command may be used to project a grid
as well.
The PROTECT Function
Converts a grid between two coordinate systems.
PROJECT(, {projection_file},
{NEAREST I BILINEAR I CUBIC}, {out_cellsize})
is the grid whose coordinates are to be projected.
{projection_file} is the name of an ASCII text file used to define
the input and output projections. If no projection file is
specified, the user is prompted to enter the input and output
projections using subcommands just like the ARC PROJECT
command.
{NEAREST} means cells are resmapled using the nearest
neighbor algorithm
{BILINEAR} means cells are resmapled using bilinear
interpolation.
{CUBIC} means cells are resmapled using cubic convolution.
{out_cellsize} is the size in map units of the cells in the output
grid.
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Raster to Vector Conversion
Coverages are the primary source for creating grids. Equally
important is the ability to convert grids into vector coverages.
This section addresses the ARC commands and GRID functions
available for raster to vector conversion.
The GRIPLINE Function
Converts a grid representing raster linear features into a line
coverage.
GRIDLINE(, {POSITIVE I DATA}, {THIN I NOTHIN},
{NOFILTER I FILTER}, {ROUND I SHARP},
{item}, {thickness}, {dangle}, {weed})
is the grid to vectorize.
{POSITIVE} means only cell values greater than or equal to 0
will be vectorized.
{DATA} means all cells will be converted except those assigned
NODATA.
{THIN} means foreground cells will be thinned.
{NOTHIN} means no thinning will occur.
{NOFILTER} is the default and means no filter will be applied.
{FILTER} means the grid will be filtered to smooth boundaries.
{ROUND} rounds corners and junctions. This is useful for grids
representing man-made features such as streets.
{SHARP} preserves rectangular corners and junctions. This is
useful for grids representing natural features such as streams.
{item} is the item in the AAT to receive the grid cell values. If #
is entered, no item is written to the AAT.
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The GRIDLINE Function (Continued)
{thickness} is the maximum thickness, in map units, of the linear
features in the grid.
{dangle} is the minimum length, in map units, of dangling arcs
that will be retained. The default is 0.7 times the thickness if
THIN is used, and 2 times the thickness if NOTHIN is used.
{weed} is specified in map units and is used to generalize arcs.
The default is 0.0.
The GRIDPOINT Function
Converts a grid representing raster point features to a point
coverage.
GRIDPOINT(, {patjtem})
is the input grid.
{pat_item} is the item in the PAT which will hold the cell value.
If not specified
The points are positioned at the center of cells they represent.
Only NOD ATA cells will not be converted.
The GRIDPOLY Function
Converts a grid to a polygon coverage. Polygons are built from
groups of contiguous cells having the same cell value.
GRIDPOLY(, {weed_tolerance})
is the grid to vectorize.
{weed_tolerance} is used to generalize arcs. The default is 0.0.
In most cases, the weed tolerance should be less than 2.5 times
the cell size.
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The ARC GRID ASCII Command
Converts a grid into an ASCII file.
Usage: GRID ASCII {item}
is the grid to be converted.
is the output ASCII file.
{item} is the name of the input grid item whose value will be
connected to the ASCII file. The item must be numeric and
defaults to VALUE.
GRIDASCII is useful for creating an ASCII file version of a
grid. The file is formatted as a matrix so that programming
language such as C can easily read and process the matrix to
perform operations not available within GRID. The C program
can create a new ASCII file to hold the processing results which
can be converted into a grid using the ASCIIGRID command.
The ARC GRIDLINE Command
Converts a grid representing raster linear features into a line
coverage.
ฎ Usage: GRIDLINE {POSITIVE I DATA}
{NOTHIN I THIN} {NOFILTER I FILTER}
{ROUND I SHARP} {item} {thickness}
{dangle} {weed}
is the grid to vectorize.
ฎ is the output line coverage created.
{POSITIVE} means only cell values greater than or equal to 0
will be vectorized.
{DATA} means all cells will be converted except those assigned
NODATA.
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The ARC GRIDLINE Command (Continued)
September 16. 1995
{THIN} means foreground cells will be thinned.
{NOTHIN} means no thinning will occur.
{NOFILTER} is the default and means no filter will be applied.
{FILTER} means the grid will be filtered to smooth boundaries.
{ROUND} rounds corners and junctions. This is useful for grids
representing man-made features such as streets.
{SHARP} preserves rectangular corners and junctions. This is
useful for grids representing natural features such as streams.
{item} is the item in the AAT to receive the grid cell values. If #
is entered, no item is written to the AAT.
{thickness} is the maximum thickness, in map units, of the linear
features in the grid.
{dangle} is the minimum length, in map units, of dangling arcs
that will be retained. The default is 0.7 times the thickness if
THIN is used, and 2 times the thickness if NOTHIN is used.
{weed} is specified in map units and is used to generalize arcs.
The default is 0.0.
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The ARC GRIDPOINT Command
Converts a grid representing raster point features to a point
coverage.
Usage: GRIDPOINT {pat_item}
is the input grid to convert.
e is the output point coverage.
{pat_item} is the item in the PAT which will hold the cell value.
If not specified
The points are positioned at the center of cells they represent.
Only NOD ATA cells will not be converted.
The ARC GRIDPOLY Command
Converts a grid to a polygon coverage. Polygons are built from
groups of contiguous cells having the same cell values.
Usage: GRIDPOLY {weed_tolerance>
is the input grid to convert.
is the output polygon coverage.
{weed_tolerance} is used to generalize arcs. The default is 0.0.
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Focal Functions
Focal functions compute an output grid where the output value
at each location is a function of the input cell(s) in some
specified neighborhood of the location. The focal functions
within grid are:
FOCALVARIETY
The FOCALFLOW Function
Determines the flow into a cell from its immediate
neighborhood.
FOCALFLOW (, {thresh_value})
is the grid the flow is calculated for.
{thresh_value} defines the threshold value which must be met or
exceeded before flow can occur. If the difference between the
value at a neighboring cell is less than or equal to the threshold,
the output will be assigned 0 for no flow.
The output grid is always integer.
The resulting value measure flow into a cell.
FOCALFLOW uses the immediate 3x3 cell neighborhood to
determine which of a cell's eight neighbors flows into it.
Many times the flow values represent fluid movement, such as
water moving across an elevation or slope surface, but can be
any user-defined movement.
FOCALFLOW FOCALMAJORITY
FOCALMEAN FOCALMEDIAN
FOCALRANGE FOCALSTD
FOCALMAX
FOCALMIN
FOCALSUM
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The FOCALMATORITY Function
For each cell location on an input grid, finds the majority value
(the value that appears most often) within a specified
neighborhood and sends it to the corresponding cell location on
the output grid.
FOCALMAJORITY (, {DATA I NODATA})
FOCALMAJORITY (, , ,
, {DATA I NODATA})
FOCALMAJORITY (, , ,)
{DATA I NODATA})
FOCALMAJORITY (, , /
{DATA I NODATA})
FOCALMAJORITY (, , ,
, {DATA I NODATA})
FOCALMAJORITY (, , ,
, , {DATA I NODATA})
is the input grid.
The default neighborhood is a 3x3 rectangle.
/ , defines the
shape of the neighborhood to be a donut. Cells outside the
inner radius but inside the outer radius are included in the
neighborhood processing.
, defines the shape of the neighborhood as a
circle. Cells within the circle are processed as part of the
neighborhood.
, defines the shape of an irregular
neighborhood based on a kernel file. The kernel file must have
the width and height (in the number of cells) listed as the first
record of the file. All subsequent lines represent the
neighborhood matrix. Cells with 0 are not processed, and all
non-zero cells are considered to be in the neighborhood.
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The FOCALMATORITY Function (Continued)
, , defines the shape of the
neighborhood as a rectangle. Cells within the rectangle are
processed as part of the neighborhood.
, , ,
{DATA} specifies that if a cell has a value of NODATA in a
neighborhood, the NODATA will be ignored.
{NODATA} specifies that if a cell has a value of NODATA in a
neighborhood, the output cell being processed will be assigned
NODATA.
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The FOCALMAX Function
For each cell location on an input grid, finds the highest value
within a specified neighborhood and sends it to the
corresponding cell location on the output grid.
FOCALMAX (, {DATA I NODATA})
FOCALMAX (, , ,
, {DATA I NODATA})
FOCALMAX (, , ,)
{DATA I NODATA})
FOCALMAX (, , ,
{DATA I NODATA})
FOCALMAX (, , , ,
{DATA I NODATA})
FOCALMAX (, , , ,
, {DATA I NODATA})
is the input grid.
The default neighborhood is a 3x3 rectangle.
, , defines the
shape of the neighborhood to be a donut. Cells outside the
inner radius but inside the outer radius are included in the
neighborhood processing.
, defines the shape of the neighborhood as a
circle. Cells within the circle are processed as part of the
neighborhood.
, defines the shape of an irregular
neighborhood based on a kernel file. The kernel file must have
the width and height (in the number of cells) listed as the first
record of the file. All subsequent lines represent the
neighborhood matrix. Cells with 0 are not processed, and all
non-zero cells are considered to be in the neighborhood.
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The FOCALMAX Function (Continued)
, , defines the shape of the
neighborhood as a rectangle. Cells within the rectangle are
processed as part of the neighborhood.
, , ,
{DATA} specifies that if a cell has a value of NODATA in a
neighborhood, the NODATA will be ignored.
{NODATA} specifies that if a cell has a value of NODATA in a
neighborhood, the output cell being processed will be assigned
NODATA.
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The FOCALMEAN Function
For each cell location on an input grid, finds the mean value
within a specified neighborhood and sends it to the
corresponding cell location on the output grid.
FOCALMEAN (, {DATA I NOD ATA})
FOCALMEAN (, , ,
, {DATA I NOD ATA})
FOCALMEAN (, , ,)
{DATA I NODATA})
FOCALMEAN (, , ,
{DATA I NODATA})
FOCALMEAN (, , , ,
{DATA I NODATA})
FOCALMEAN (, , , ,
, {DATA I NODATA})
FOCALMEAN (, , ,
{DATA I NODATA})
is the input grid.
The default neighborhood is a 3x3 rectangle.
, , defines the
shape of the neighborhood to be a donut. Cells outside the
inner radius but inside the outer radius are included in the
neighborhood processing.
, defines the shape of the neighborhood as a
circle. Cells within the circle are processed as part of the
neighborhood.
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The FOCALMEAN Function (Continued)
, defines the shape of an irregular
neighborhood based on a kernel file. The kernel file must have
the width and height (in the number of cells) listed as the first
record of the file. All subsequent lines represent the
neighborhood matrix. Cells with 0 are not processed, and all
non-zero cells are considered to be in the neighborhood.
, , defines the shape of the
neighborhood as a rectangle. Cells within the rectangle are
processed as part of the neighborhood.
, , /
{DATA} specifies that if a cell has a value of NODATA in a
neighborhood, the NODATA will be ignored.
{NODATA} specifies that if a cell has a value of NODATA in a
neighborhood, the output cell being processed will be assigned
NODATA.
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The FOCALMEDIAN Function
For each cell location on an input grid, finds the median value
within a specified neighborhood and sends it to the
corresponding cell location on the output grid.
FOCALMEDIAN (, {DATA I NODATA})
FOCALMEDIAN (, , ,
, {DATA I NODATA})
FOCALMEDIAN (, , ,)
{DATA I NODATA})
FOCALMEDIAN (, , ,
{DATA I NODATA})
FOCALMEDIAN (, , , ,
{DATA I NODATA})
FOCALMEDIAN (, , , ,
, {DATA I NODATA})
is the input grid.
The default neighborhood is a 3x3 rectangle.
, , defines the
shape of the neighborhood to be a donut. Cells outside the
inner radius but inside the outer radius are included in the
neighborhood processing.
, defines the shape of the neighborhood as a
circle. Cells within the circle are processed as part of the
neighborhood.
, defines the shape of an irregular
neighborhood based on a kernel file. The kernel file must have
the width and height (in the number of cells) listed as the first
record of the file. All subsequent lines represent the
neighborhood matrix. Cells with 0 are not processed, and all
non-zero cells are considered to be in the neighborhood.
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The FOCALMEDIAN Function (Continued)
/ , defines the shape of the
neighborhood as a rectangle. Cells within the rectangle are
processed as part of the neighborhood.
, , ,
{DATA} specifies that if a cell has a value of NODATA in a
neighborhood, the NODATA will be ignored.
{NODATA} specifies that if a cell has a value of NODATA in a
neighborhood, the output cell being processed will be assigned
NODATA.
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The FOCALMIN Function
For each cell location on an input grid, finds the minimum value
within a specified neighborhood and sends it to the
corresponding cell location on the output grid.
FOCALMIN (, {DATA I NODATA})
FOCALMIN (/ , ,
, {DATA I NODATA})
FOCALMIN (, , ,)
{DATA I NODATA})
FOCALMIN (, , /
{DATA I NODATA})
FOCALMIN (, , , ,
{DATA I NODATA})
FOCALMIN (, , , ,
, {DATA I NODATA})
is the input grid.
The default neighborhood is a 3x3 rectangle.
/ , defines the
shape of the neighborhood to be a donut. Cells outside the
inner radius but inside the outer radius are included in the
neighborhood processing.
, defines the shape of the neighborhood as a
circle. Cells within the circle are processed as part of the
neighborhood.
, defines the shape of an irregular
neighborhood based on a kernel file. The kernel file must have
the width and height (in the number of cells) listed as the first
record of the file. All subsequent lines represent the
neighborhood matrix. Cells with 0 are not processed, and all
non-zero cells are considered to be in the neighborhood.
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The FOCALMIN Function (Continued)
, , defines the shape of the
neighborhood as a rectangle. Cells within the rectangle are
processed as part of the neighborhood.
, , ,
{DATA} specifies that if a cell has a value of NODATA in a
neighborhood, the NODATA will be ignored.
{NODATA} specifies that if a cell has a value of NODATA in a
neighborhood, the output cell being processed will be assigned
NODATA.
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The FOCALRANGE Function
For each cell location on an input grid, finds the range of values
within a specified neighborhood and sends it to the
corresponding cell location on the output grid.
FOCALRANGE (, {DATA I NODATA})
FOCALRANGE (, , ,
, {DATA I NODATA})
FOCALRANGE (, , ,)
{DATA I NODATA})
FOCALRANGE (, , ,
{DATA I NODATA})
FOCALRANGE (, , , ,
{DATA I NODATA})
FOCALRANGE (, , , ,
, {DATA I NODATA})
is the input grid.
The default neighborhood is a 3x3 rectangle.
, , defines the
shape of the neighborhood to be a donut. Cells outside the
inner radius but inside the outer radius are included in the
neighborhood processing.
, defines the shape of the neighborhood as a
circle. Cells within the circle are processed as part of the
neighborhood.
, defines the shape of an irregular
neighborhood based on a kernel file. The kernel file must have
the width and height (in the number of cells) listed as the first
record of the file. All subsequent lines represent the
neighborhood matrix. Cells with 0 are not processed, and all
non-zero cells are considered to be in the neighborhood.
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The FOCALRANGE Function (Continued)
, , defines the shape of the
neighborhood as a rectangle. Cells within the rectangle are
processed as part of the neighborhood.
, , ,
{DATA} specifies that if a cell has a value of NODATA in a
neighborhood, the NODATA will be ignored.
{NODATA} specifies that if a cell has a value of NODATA in a
neighborhood, the output cell being processed will be assigned
NODATA.
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The FOCALSTD Function
For each cell location on an input grid, finds the standard
deviation of values within a specified neighborhood and sends
it to the corresponding cell location on the output grid.
FOCALSTD (, {DATA I NODATA})
FOCALSTD (, , ,
, {DATA I NODATA})
FOCALSTD (, , ,)
{DATA I NODATA})
FOCALSTD (, , ,
{DATA I NODATA})
FOCALSTD (, , , ,
{DATA I NODATA})
FOCALSTD (, , , ,
, {DATA I NODATA})
FOCALSTD (, , ,
{DATA I NODATA})
is the input grid.
The default neighborhood is a 3x3 rectangle.
/ , defines the
shape of the neighborhood to be a donut. Cells outside the
inner radius but inside the outer radius are included in the
neighborhood processing.
, defines the shape of the neighborhood as a
circle. Cells within the circle are processed as part of the
neighborhood.
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The FOCALSTD Function (Continued)
September 16.1995
, defines the shape of an irregular
neighborhood based on a kernel file. The kernel file must have
the width and height (in the number of cells) listed as the first
record of the file. All subsequent lines represent the
neighborhood matrix. Cells with 0 are not processed, and all
non-zero cells are considered to be in the neighborhood.
, , defines the shape of the
neighborhood as a rectangle. Cells within the rectangle are
processed as part of the neighborhood.
, , ,
{DATA} specifies that if a cell has a value of NODATA in a
neighborhood, the NODATA will be ignored.
{NODATA} specifies that if a cell has a value of NODATA in a
neighborhood, the output cell being processed will be assigned
NODATA.
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The FOCALSUM Function
For each cell location on an input grid, finds the sum of values
within a specified neighborhood and sends it to the
corresponding cell location on the output grid.
FOCALSUM (, {DATA I NODATA})
FOCALSUM (, , ,
, {DATA I NODATA})
FOCALSUM (, , ,)
{DATA I NODATA})
FOCALSUM (, , ,
{DATA I NODATA})
FOCALSUM (, , , ,
{DATA I NODATA})
FOCALSUM (, , , ,
, {DATA I NODATA})
FOCALSUM (, , ,
{DATA I NODATA})
is the input grid.
The default neighborhood is a 3x3 rectangle.
, , defines the
shape of the neighborhood to be a donut. Cells outside the
inner radius but inside the outer radius are included in the
neighborhood processing.
, defines the shape of the neighborhood as a
circle. Cells within the circle are processed as part of the
neighborhood.
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The FOCALSUM Function (Continued)
/ defines the shape of an irregular
neighborhood based on a kernel file. The kernel file must have
the width and height (in the number of cells) listed as the first
record of the file. All subsequent lines represent the
neighborhood matrix. Cells with 0 are not processed, and all
non-zero cells are considered to be in the neighborhood.
, , defines the shape of the
neighborhood as a rectangle. Cells within the rectangle are
processed as part of the neighborhood.
, , /
{DATA} specifies that if a cell has a value of NODATA in a
neighborhood, the NODATA will be ignored.
{NODATA} specifies that if a cell has a value of NODATA in a
neighborhood, the output cell being processed will be assigned
NODATA.
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The FOCALVARIETY Function
For each cell location on an input grid, finds the number of
unique values within a specified neighborhood and sends it to
the corresponding cell location on the output grid.
FOCALVARIETY (, {DATA I NOD ATA})
FOCALVARIETY (, , ,
, {DATA I NODATA})
FOCALVARIETY (, , ,)
{DATA I NODATA})
FOCALVARIETY (, , ,
{DATA I NODATA})
FOCALVARIETY (, , , ,
{DATA I NODATA})
FOCALVARIETY (, , , ,
, {DATA I NODATA})
is the input grid.
The default neighborhood is a 3x3 rectangle.
, , defines the
shape of the neighborhood to be a donut. Cells outside the
inner radius but inside the outer radius are included in the
neighborhood processing.
, defines the shape of the neighborhood as a
circle. Cells within the circle are processed as part of the
neighborhood.
, defines the shape of an irregular
neighborhood based on a kernel file. The kernel file must have
the width and height (in the number of cells) listed as the first
record of the file. All subsequent lines represent the
neighborhood matrix. Cells with 0 are not processed, and all
non-zero cells are considered to be in the neighborhood.
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GRID Functions
The FOCALVARIETY Function (Continued)
, , defines the shape of the
neighborhood as a rectangle. Cells within the rectangle are
processed as part of the neighborhood.
, , /
{DATA} specifies that if a cell has a value of NODATA in a
neighborhood, the NODATA will be ignored.
{NODATA} specifies that if a cell has a value of NODATA in a
neighborhood, the output cell being processed will be assigned
NODATA.
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The Zonal Functions
Zonal functions create an output grid on which the computation
of the desired function occurs on the cell values from the input
value grid that intersect or fall within each zone in the specified
input zone grid.
The input zone grid is only used to define the size, shape, and
location of each zone.
The input value grid is used to identify the values to be used in
the evaluation within the zone.
Zonal functions compute statistics or identify features on the
values from the value grid that intersect the zones defined by
values of the zone grid.
The following section presents a description and usage of each
zonal function.
The ZONALAREA Function
Calculates the area of each zone in the input grid within the
analysis window.
Usage: (F) ZONALAREA ()
The ZONALCENTROIP Function
Creates a grid of cells locating the centroids of each zone of an
input grid.
Usage: (I) ZONALCENTROID ()
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The ZONALFILL Function
Fills zones using the minimum cell value from a weight grid,
along the zone boundary.
Usage: (I) ZONALFILL (, )
The ZONALGEOMETRY Function
Calculates for each zone of the input grid its area, perimeter,
thickness, and the characteristics of ellipse and records them in
the output INFO table.
Usage: (T) ZONALGEOMETRY (, {geometry_type},
{max_thickness})
The ZONALMATORITY Function
Records in each output cell the majority value (the value that
occurs most often) of all cells in the that belongs
to the same zone as the output cell. Zones are identified by the
values of the cells in the input .
Usage: (*) ZONALMAJORITY (, ,
{DATA I NOD AT A})
The ZONALMAX Function
Records in each output cell the maximum value of all cells in the
that belongs to the same zone as the output cell.
Zones are identified by the values of the cells in the input
.
Usage: (*) ZONALMAX (, ,
{DATA I NODATA})
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fiftptftmber 16. 1995
The ZONALMEAN Function
Records in each output cell the mean value of all cells in the
that belongs to the same zone as the output cell.
Zones are identified by the values of the cells in the input
.
Usage: (F) ZONALMEAN (, /
{DATA I NODATA})
The ZONALMEDIAN Function
Records in each output cell the median value of all cells in the
that belongs to the same zone as the output cell.
Zones are identified by the values of the cells in the input
.
Usage: (*) ZONALMEDIAN (, ,
{DATA I NODATA})
The ZONALMIN Function
Records in each output cell the minimum value of all cells in the
that belongs to the same zone as the output cell.
Zones are identified by the values of the cells in the input
.
Usage: (*) ZONALMIN (, ,
{DATA I NODATA})
The ZONALPERIMETER Function
o Calculates the perimeter of each zone in the input grid within
the analysis window.
Usage: (I) ZONALPERIMETER ()
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The ZONALRANGE Function
Records in each output cell the range of values of all cells in the
that belongs to the same zone as the output cell.
Zones are identified by the values of the cells in the input
.
Usage: (*) ZONALRANGE (, /
{DATA I NODATA})
Usage: (*) ZONALRANGE (, ,
{DATA I NODATA})
The ZONALSTATS Function
Records in an output INFO table the mean, minimum,
maximum, range, sum, standard deviation, variety, majority, and
median of the values of all cells in the value grid that belong to
the same zone. Zones are identified by the values of the cells in
the input zone grid.
Usage: (T) ZONALSTATS (, ,
{stats_name}, {DATA I NODATA})
The ZONALSTD Function
Records in each output cell the standard deviation of all cells in
the that belongs to the same zone as the output
cell. Zones are identified by the values of the cells in the input
.
Usage: (F) ZONALSTD (, /
{DATA I NODATA})
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The ZONALSUM Function
Records in each output cell the sum of all cells in the
that belongs to the same zone as the output cell.
Zones are identified by the values of the cells in the input
.
Usage: (*) ZONALSUM (, /
{DATA I NODATA})
The ZONALTHICKNESS Function
Calculates for each zone on an input grid the deepest or thickest
point within the zone from its surrounding cells.
Usage: (I) ZONALTHICKNESS (/{max_thickness})
The ZONALVARIETY Function
Records in each output cell the variety (the number of unique
values) of all cells in the that belongs to the same
zone as the output cell. Zones are identified by the values of the
cells in the input .
Usage: (I) ZONALVARIETY (, /
{DATA I NODATA})
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Surface Analysis
Surface Analysis
Surfaces can be stored as integer or floating point grids.
The surface view of a grid considers the value of each cell as a
point, at the center of the cell. The value of other locations
within the same cell can be interpolated from the cell center and
the center of neighboring cells.
GRID provides four functions which generate floating point
grids from a point data set. This point data set can be a point
coverage or an ASCII file of x,y,z values in ARC GENERATE
format. The points can be randomly distributed in space.
The four surface generators are inverse distance weighted
interpolation (IDW), trend surface interpolation, kriging, and
spline.
The distribution of sample points and the type of surface you
are trying to generate (simulate) determines which surface
generation method to use.
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Surface Analysis
The IDW Function
Performs an inverse distance weighted interpolation on a point
data set.
IDW (, {spot_item},
{barriers}, {power}, {SAMPLE, {num_points},
{max_radius}}, {cellsize}, {xmin, ymin, xmax, ymax})
IDW (, {spot_item}, {barriers},
{power}, {RADIUS, {radius}, {min_points}},
{cellsize}, {xmin, ymin, xmax, ymax})
IDW allows you to control the significance of known points
upon the interpolated values, based upon their distance from
the output point. The {power} option can be used to change the
interpolation from local to global. A larger power will result in
lesser influence from surrounding points.
The output values for a cell using IDW is limited to the range of
values used to interpolate.
The influence of an input point on an interpolated value is
isotropic. Since the influence of an input point on an
interpolated value is distance related, IDW is not ridge
preserving.
The best results from IDW are obtained when sampling is
sufficiently dense in regard to the local variation you are
attempting to simulate. If the input points are sparse or very
uneven, the results may not sufficiently represent the desired
surface.
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Surface Analysis
The KRIGING Function
Interpolates a grid from a set of points using kriging.
Usage: (F) KRIGING (, {spot_item},
{barrier_cover I barrier_file},
{BOTH I GRAPH I GRID}, {output_variance},
{method}, {SAMPLE, {num_points}, {max_radius}},
{cellsize}, {xmin, ymin, xmax, ymax})
KRIGING (, {spot_item},
{barrier_cover I barrier_file},
{BOTH I GRAPH I GRID}, {output_variance},
{method}, {RADIUS, {radius}, {min_points}},
{cellsize}, {xmin, ymin, xmax, ymax})
Kriging is based on the regionalized variable theory that
assumes that the spatial variation in the phenomenon
represented by the z values is statistically homogeneous
throughout the surface.
Each kriging method uses a mathematical function to model the
spatial variation in z values within the input sample points. The
variations are measured using semi-variance.
The key to reviewing semi-variance is the creation of a semi-
variogram. This can be done with the KRIGING GRAPH and
BOTH options and using the Arcplot SEMIVARIOGRAM
command to review the semi-variogram.
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Surface Analysis
The TREND Function
Performs a trend interpolation on a point data set.
Usage: (F) TREND (, {spot_item},
{order}, {LINEAR I LOGISTIC},
{cellsize}, {xmin, ymin, xmax, ymax})
The trend surface interpolator uses a polynomial regression to
fit a least-squares surface to the input points. The trend
interpolator allows the user control over the order of the
polynomial used to fit the surface.
A first-order trend surface interpolation performs a least-
squares fit of a plane to the set of input points.
As the order of the polynomial is increased, the surface becomes
progressively more complex.
Trend surface interpolation creates smooth surfaces. The
surface generated will seldom pass through the original data
points since it performs a best fit for the entire surface.
The most common order of polynomials is 1 to 3.
The SPLINE Function
Performs a two-dimensional minimum curvature spline
interpolation on a point data set resulting in a smooth surface
that passes exactly through the input points.
Usage: (F) SPLINE (, {spot_item},
{REGULARIZED I TENSION}, {weight}, {num_points},
{cellsize}, {xmin, ymin, xmax, ymax})
Spline is also referred to as thin plate interpolation. It ensures a
smooth and continuous surface together with first-derivative
surfaces.
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Surface Analysis
Surface Defined Grids
Slope identifies the maximum rate of change in value from each
cell to its neighbors. An output slope grid can be calculated as
percent slope or degree of slope.
Aspect identifies the down-slope direction of the maximum rate
of change in value from each cell to its neighbors. The output
will be a grid of compass directions of the aspect (aspect can be
thought of as the slope direction).
Analytical hillshading is a way to determine the hypothetical
illumination of a surface for analytical or graphical reasons.
The SLOPE Function
Identifies the rate of maximum change in z values from each
cell.
SLOPE (, {DEGREE I PERCENTAGE})
SLOPE (, , {DEGREE I PERCENTAGE})
is the input surface.
{DEGREE} calculates slope in degrees.
{PERCENTAGE} calculates slope as the percent rise.
is the number of ground x,y units in one surface z
unit. Its use is essential when surface z units are expressed in
units different from the ground units.
If the center of a cell in the immediate 3x3 neighborhood is
NODATA, the output is NODATA.
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Surface Analysis
The ASPECT Function
Identifies the direction of maximum rate of change in the z
value from each cell.
ASPECT ()
Aspect is expressed in positive degrees from 0 to 360, measured
clockwise from north.
Cells in the input of zero slope are assigned an aspect of -1.
If the center of a cell in the immediate 3x3 neighborhood is
NOD ATA, the output is NOD ATA.
If any neighborhood cells are NODATA, they are assigned the
values of the center cell then the aspect is computed.
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Surface Analysis
The HILLSHADE Function
Creates a shaded relief grid from a grid by considering the
illumination angle and shadows.
HILLSHADE (, {azimuth}, {altitude},
{ALL I SHADE I SHADOW}, {z_factor})
is the input grid.
{azimuth} is the azimuth angle of the light source measured
clockwise from 0 to 360 degrees from north. The default is 315.
{altitude} is the slope or angle of the illumination source above
the horizon measured from 0 to 90 degrees.
{ALL} considers both local illumination angles and shadows.
Output values range from 0 to 255.
{SHADE} considers local illumination angles where shadows are
not considered. Output values range from 0 to 255.
{SHADOW} creates a binary grid (1 is light and 0 is shadow).
is the number of ground x,y units in one surface z
unit. Its use is essential when surface z units are expressed in
units different from the ground units.
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Surface Analysis
The SAI Command
Creates an output grid containing a slope-aspect index, or a
lookup table of hypothetical illumination to be used for
displaying such as grid.
Usage: SAI {z_factor}
Usage: SAI {azimuth} {altitude}
is a surface grid.
is the output slope-aspect index grid.
the name of the output colormap file based
on azimuth and altitude.
{azimuth} is the angle of the illumination source from north,
from 0 to 360 degrees measured clockwise, where north is 0
degrees and east is 90 degrees. The default is 315 degrees.
{altitude} is the angle of the illumination source above the
horizon, 0 to 90 degrees where 45 is the default.
A sample output of Mount St. Helens created with SAI was
created using the command "gridpaint surfsai # # #
surfsai.cmf".
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Distance Functions
Distance Functions
The following table presents the distance functions within
GRID:
Distance Function
Description
CORRIDOR
Records for each cell location in the sum of accumulative
costs for two input accumulative-cost grids.
COST ALLOCATION
Identifies for each cell the zone of each source cell that could
be reached with the least accumulative cost.
COSTBACKLINK
Defines the neighbor that is the next cell on the least-
accumulative cost path from a cell to a set of source cells.
COSTDISTANCE
Calculates for each cell the least-accumulative-cost distance
over a cost surface to a source cell or a set of source cells.
COSTPATH
Produces an output grid that records the least-cost path(s)
from selected cells in the input grid to the closest source cell
defined within the accumulative-cost grid in terms of cost
distance.
EU ALLOCATION
Calculates for each cell the zone of the source cell (in
Euclidean distance).
EUDIRECTION
Calculates the direction in degrees that each cell center is
from the closest source. The output values are based on
compass direction, with 0 degrees being reserved for the
source cell.
EUDISTANCE
Calculates for each cell the Euclidean distance to the closest
cell.
PATHDISTANCE
Calculates for each cell the least-accumulative-cost distance
over a cost surface from a source cell or set of source cells
which accounting for surface distance and horizontal and
vertical cost factors.
ฉ1995 A.C.T. GIS, Inc.
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Surface Hydrologic Analysis
Surface Hvdrologic Analysis
The shape of a surface determines how water will flow across it.
Using a DEM as input, it is possible to delineate a drainage
system and then quantify the characteristics of that system.
The GRID tools let you determine for any location on a surface,
the upslope area contributing to that point, and the downslope
path water would flow.
Watersheds and stream networks created from DEMs using
GRID are the primary inputs to most surface hydrologic models.
Surface hydrologic models can determine the height, timing,
and inundation of a flood, as well as locating areas contributing
to pollutants in a stream, or predicting the effects of altering the
landscape.
DEMs
A DEM is a raster representation of a continuous surface,
usually referring to the surface of the Earth. The accuracy of a
DEM depends on how it was sampled, the spacing of points,
and the data type (integer or floating point).
Errors in DEMs are usually classified as sinks or peaks.
A sink is an area surrounded by higher elevation values.
A peak is an area surrounded by lower elevation values.
Errors such as sinks should be removed before attempting to
derive surface information since flow direction can be adversely
affected.
The number of sinks in a DEM is usually higher when the
resolution becomes coarser. Sinks can also be caused by stored
surface values as integers.
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Surface Hydrologic Analysis
Creating a Depressionless DEM
Sinks can be located using the SINK function, and can be filled
with the GRID FILL command.
The SINK Function
Creates a grid, identifying all sinks (areas of internal drainage).
SINK ()
is a grid showing the direction of flow out of each
cell. It can be created with the FLOWDIRECTION function.
The output of the SINK function is an integer grid with each
sink being assigned a unique value (numbered between 1 and
the total number of sinks).
Sinks in elevation data are commonly due to errors in the data.
They should be removed in order to be able to create an accurate
representation of flow direction.
The example below presents the creation of a sink grid:
Grid: sinkgrid = sink(flowdiretion(elev_grid))
It is sometimes useful to know the depth of a sink or group of
sinks. This information can be used to determine an
appropriate {z_limit} for the FILL function. A grid of sinks
coded with depth can be created by first running the SINK
function to locate sinks in a grid:
Grid: flowdir = (flowdiretion(demlat)
Grid: sinkgrid = sink(flowdir)
Then use the WATERSHED function to create a grid of the
contributing area of each sink:
Grid: sink_areas = watershed(flowdir, sinkgrid)
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The SINK Function (Continued)
Then create a grid of minimum elevation in the watershed of
each sink:
Grid: sink_min = zonalmin(sink_areas/ demlat)
Then create a grid of maximum elevation in the watershed of
each sink:
Grid: sink_max = zonalfill(sink_areas, demlat)
Then subtract the minimum value from the maximum value to
find the depth:
Grid: sink_depth = sink_max - sink_min
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Surface Hydrologic Analysis
The FILL Command
Fills sinks (areas of internal drainage) or levels peaks in a
continuous grid to remove small imperfections in the data.
FILL {SINK I PEAK}
{z_limit} {out_dir_grid}
is the surface grid.
is the grid that has its sinks filled or peaks cut.
{SINK} specifies that all sinks that are less than {z_limit} lower
than their lowest adjacent neighbor will be filled to the height
of their pour point.
{PEAK} specifies that all peaks less than the {z_limit} that are
higher than the highest adjacent neighbor will be cut down to
the height of their neighbor.
{z_limit} is the maximum difference between a sink and its pour
point or a peak and its highest adjacent neighbor. {z_limit} is
expressed in map units and can be thought of as the depth of all
sinks that will be removed.
{out_dir_grid} is an optional output grid that stores the flow
direction from each cell to the steepest downslope neighbor.
This is the same as the output of the FLOWDIRECTION
function.
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Surface Hydrologic Analysis
The FLOWDIRECTION Function
Determines the direction of flow from every cell to its steepest
downslope neighbor.
FLOWDIRECTION (, {o_drop_grid},
{NORMAL I FORCE})
is the input surface grid representing elevations.
{o_drop_grid} is an optional output grid showing the ratio of
maximum change in elevation from each cell along the direction
of flow, to the path length between centers of cells, expressed in
percents.
{NORMAL} specifies if the maximum drop on the inside of an
edge cell is greater than 0, the flow direction will be determined
as usual. Otherwise, flow direction will be toward the edge.
{FORCE} specifies that all cells at the edge of the surface grid
will flow outward from the surface grid.
The output is a grid with values from 1 to 255
Downstream tracing can be performed using the flow direction
grid as a backlink grid for input into the COSTPATH function.
If all neighbors are higher than the processing cell, the
neighborhood is enlarged until a steepest descent is found.
If all neighbors are higher than the processing cell, it will be
considered noise and filled to the lowest value of its neighbors
and have a flow direction towards this cell.
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Surface Hydrologic Analysis
The FLOW ACCUMULATION Function
Creates a grid of accumulated flow to each cell by accumulating
the weight of all cells that flow into each downslope cell.
FLOWACCUMULATION (, {weight_grid})
is the input grid showing direction of flow out of
each cell.
{weight_grid} is the weight assigned to each cell. If not
specified, a default weight of one will be applied to each cell.
For each cell in the output grid, the result will be the number of
cells that flow into it.
The {weight_grid} could be a continuous grid representing
rainfall during a given storm. FLOWACCUMULATION could
be used to determine how much rain has fallen within a given
watershed. The output would be the amount of rain that has
that would flow through each cell, assuming all rain became
runoff.
Output cells with a flow accumulation of 0 are local topographic
highs and are used to identify ridges.
Cells of high accumulated flow are areas of concentrated flow
and may be used to identify stream channels.
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Surface Hydrologic Analysis
The FLOWLENGTH Function
Calculates upstream and downstream distance along a flow path
for each cell.
FLOWLENGTH (, {weight_grid},
{DOWNSTREAM I UPSTREAM})
is a grid indicating direction of flow.
{weight_grid} is a grid defining impedance or resistance to flow
through each cell. The value at each cell represents the cost per
unit distance of moving through the cell. Each cell location is
multiplied by the cell resolution to obtain the total cost of
passing through the cell.
{DOWNSTREAM} calculates the downslope distance along the
flow path from each cell to a sink or outlet on the edge of a grid.
{UPSTREAM} calculates the upstream distance along the flow
path, from each cell to the top of the drainage divide.
FLOWLENGTH is used to calculate the length of the longest
flow path within a given basin. The measure is often used to
calculate the time of concentration of a basin (using the
UPSTREAM option).
FLOWLENGTH can also be used to create distance-area
diagrams of hypothetical rainfall/runoff events using the
weight_grid as an impedance to movement downslope.
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Surface Hydrologic Analysis
The BASIN Function
Creates a grid delineating all drainage basins within the
analysis window.
BASIN ()
is a grid showing direction of flow out of each cell.
It can be created using the FLOWDIRECTION function.
Best results are obtained when the NORMAL option is used
with the FLOWDIRECTION function.
All cells will belong to a basin, even if the basin is made up of
one cell.
Basins are identified by ridge lines between basins.
The drainage basins are created by locating the pour points at
the edge of the analysis window (where water would pour out
of the grid) as well as sinks, then identifying the contributing
area above each pour point.
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Surface Hydrologic Analysis
The WATERSHED Function
Determines the contributing area above a set of cells in a grid.
WATERSHED (, )
is a grid showing direction of flow out of each cell.
It can be created using the FLOWDIRECTION function.
is a grid representing cells above which the
contributing area, or catchment, will be determined. All cells
that are not NODATA will be used as source cells.
can be created interactively using the
SELECTPOINT function. By using the elevation grid as the
input to SELECTPOINT, the value of the resulting watersheds
will be equal to the elevation of the pour point of each
watershed.
A pour point is the point at which water flows out of an area.
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Surface Hydrologic Analysis
The STREAMLINK Function
Assigns unique values to selections of a raster linear network
between intersections.
STREAMLINK(/ )
a grid representing a raster linear network.
is a grid showing direction of flow out of each cell. It
can be created using the FLOWDIRECTION function.
Links are the sections of a stream channel connecting two
successive junctions, a junction and the outlet, or a junction and
the drainage divide.
The STREAMLINE Function
Converts a grid representing a raster linear network into a line
coverage.
STREAMLINE (, , {out_item}, {weed})
a grid representing a raster linear network.
is a grid showing direction of flow out of each cell. It
can be created using the FLOWDIRECTION function.
{out_item} is the output cover's A AT item to be assigned the
attribute of the grid cells. By default, cover-id receives the
attribute.
{weed} is the weed tolerance in map units for generalization of
arcs.
The arcs of the output cover will point downstream.
STREAMLINE is a vectorization program primarily for
vectorizing stream networks.
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Surface Hydrologic Analysis
The STREAMORDER Function
Assigns a numeric order to segments of a grid representing
branches of a linear network.
STREAMORDER (, ,
{STRAHLER I SHREVE})
a grid representing a raster linear network.
is a grid showing direction of flow out of each cell. It
can be created using the FLOWDIRECTION function.
{STRAHLER} calculates stream order as increasing only when
two streams on the same order intersect. Streams with no
tributaries are considered first order streams.
{SHREVE} calculates stream order by magnitude. All links with
no tributaries are assigned a magnitude of 1. Magnitudes are
additive downslope. When two links intersect, their
magnitudes are added and assigned to the downstream link.
The SNAPFOUR Function
Snaps selected pour points to the cell of highest flow
accumulation within a specified neighborhood.
SNAPPOUR (<* I source_grid I point_file>, ,
{snap_distance})
SNAPPOUR is used to ensure selection of points of high
accumulated flow when delineating drainage basins using the
WATERSHED function.
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Groundwater Advection and Dispersion Modeling
The functions DARCYFLOW, PARTICLETRACK, and
POROUSPUFF can be used to perform rudimentary advection-
dispersion modeling of constituents in groundwater.
The DARCYFLOW Function
Calculates the groundwater volume balance residual for steady
flow in an aquifer and the seepage velocity vector (expressed as
grids of direction and magnitude) for each cell using Darcy's
law.
DARCYFLOW (/ ,
/ /
{out_direction_grid}, {out_magnitude_grid})
DARCYFLOW is used to check the consistency of groundwater
datasets and to generate grids of groundwater flow vectors.
The PARTICLETRACK Function
Calculates the path of a particle through a velocity field,
returning an ASCII file of particle tracking data and optionally a
coverage of track information.
PARTICLETRACK (,
, <* I x,y>, {step_length}, {time}
{out_track_coverage})
The POROUSPUFF Function
Calculates the time-dependent, two-dimensional concentration
distribution in mass per volume of a solute introduced
instantaneously and at a discrete point into a vertically mixed
aquifer.
POROUSPUFF (, ,
, / {time},
{longitudinal_dispersivity}, {dispersivity_ratio}/
{retardation_factor}, {decay_coefficient})
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Visibility Functions
TheVISDECODE Command
Returns a list of observation points that can be seen by cell
locations within a specified value in the VALUE item of the
output grid from the VISIBILITY function.
VISDECODE
TheVISENCODE Command
Returns the VISIBLE-CODEs or values that are assigned to each
cell location on the output grid created by the VISIBILITY
function which can be seen by up to 16 specified observation
points.
VISENCODE
The VISIBILITY Function
Performs visibility analysis on a grid by determining how many
observation points can be seen from each cell location of the
input grid, or which cell locations can be seen by each
observation point.
VISIBILITY (, , {POINT I LINE}, {FREQUENCY I
OBSERVER}, {horizon_tolerance}
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Grid Stacks
A grid stack consists of an ordered set of spatially overlapping
grids. Stacks are created with the GRID MAKESTACK
command.
Multivariate raster data are stored within grid as a stack
consisting of a series of overlapping grids referred to as layers.
A stack is treated as a single entity for multivariate analysis.
A stack has a map extent or BND, a cell size, a data type, and a
projection.
Each layer in a stack has an index number indicating its order in
the stack. The grids that make up the stack must be in the same
workspace.
A stack is stored in a directory structure similar to a grid or
coverage. The are two files in the stack directory: an external
STK file and an ASCII PRJ file. The actual grids in the stack are
not stored in the stack directory.
The STK table stores the names of the grids in the stack and
their corresponding index value. The table has two items:
INDEX (for the layer number) and GRID (the grid name).
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Grid Stacks (Continued)
The MAKESTACK Command
Generates a grid stacks from a set of grids.
Usage: MAKESTACK LIST
Usage: MAKESTACK FILE
is the grid stack created.
LIST is the syntax for listing the grids which define
the stack.
FILE indicates a file will be used to generate the
stack. The file must begin with a record indicating the number
of grids in the stack followed by each grid in the stack listed one
line after another.
All grids to be included in the stack must exist in the current
workspace.
Multiple stacks in the same workspace can share the same
grid(s).
The STACKSHADE Command
Displays the layers (grids) of a stack using the current shadeset.
Usage: STACKSHADE
{IDENTITY I LINEAR I EQUALAREA I remap_table}
{n_pages}
is the grid stack to display.
{IDENTITY} is the default. It means no stretch is applied and
the cell value will be used as the shade symbol.
{ LINEAR} means a linear stretch will be applied. Values are
stretched from 0 to 255.
{EQUALAREA} means an equal-area stretch will be applied.
Values are stretched from 0 to 255.
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Grid Stacks (Continued)
The STACKSHADE Command
{remap_table} means a remap table will be used to determine
the symbol to be used to display each cell value.
{n_pages} is the number of sequential displays in which the
stack's layers will be drawn. The default is 1.
Each layer of a stack is given an equal area within the
MAPLIMITS.
A stack consisting of continuous data must be displayed in a
continuous color scale. RAINBOW.SHD may be used if colors
are desired.
The COPYSTACK Command
Copies a stack, including its component grids, to a new stack.
Usage: COPYSTACK {to_stack}
{OLDGRIDNAME I NEWGRIDNAME}
is the stack to copy.
{to_stack} is the name of the new stack.
{to_stack} is the new stack.
{OLDGRIDNAME} is a keyword indicating the stack and its
component grids are copied into a workspace with their original
names.
{NEWGRIDNAME} is a keyword indicating the stack and its
component grids are copied into a workspace and assigned new
names. The component grids are renamed to the name of the
new stack with "cn" appended to the end of the grid name
where n is the stack layer number.
Stacks can be copied to the same workspace only if the
{NEWGRIDNAME} option is used.
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Grid Stacks (Continued)
The DROFFROMSTACK Command
Drops one or more grids from a stack.
Usage: DROPFROMSTACK NAME
Usage: DROPFROMSTACK INDEX
is the name of the stack the layer(s) will be eliminated
from.
NAME indicates the grids will be dropped using
their grid names.
INDEX indicates the grids will be dropped
using their index or layer numbers.
Any layer in the stack may be dropped.
The BND and cell size of the stack will be updated to reflect the
remaining layers in the stack.
The STACKSTATS Command
Calculates the statistics for the layers in a stack.
Usage: STACKSTATS {out_data_file} {BRIEF I DETAIL)
is the input stack.
{out_data_file} is an optional file where the results are stored.
By default, the statistics are displayed on the screen and not
written to a file unless specified.
{BRIEF I DETAIL} determines whether just statistics (BRIEF) or
statistics and the covariance and correlation matrices are also
determined (DETAIL).
Statistics include the minimum, maximum, mean, and standard
deviation of the layers.
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AML Directives
User Environment Directives - &DESCRIBE
Stores information about a specified geo_dataset in AML
reserved variables.
Usage: &describe
is any ARC/INFO coverage, grid, grid stack,
image, tin, or lattice
&describe does not display information to the terminal like the
ARC DESCRIBE command. Instead, it sets a series of reserved
variables holding information about the specified geo_dataset.
Reserved variable prefixes are DSC$ for coverage descriptions,
GRD$ for grid descriptions, TIN$ for tin descriptions, STK$ for
grid stacks, IMG$ for images, and LAT$ for lattice descriptions.
Projection information about the geo_dataset is stored in PRJ$
reserved variables with the exception if images.
The ARC commands DESCRIBE, DESCRIBETIN, and
DESCRIBELATTICE also set the DSC$, GRD$, TIN$, and LAT$
reserved variables, respectively.
The reserved AML variables created by describing a grid or
lattice are:
Reserved GRD$ Variable
Description
GRID
grid name or lattice name
FULL_GRID
full grid name or full lattice name
DX
cellsize in X dimension; distance in X between mesh points
DY
cellsize in Y dimension; distance in Y between mesh points
XMIN
minimum X coordinate
YMIN
minimum Y coordinate
XMAX
maximum X coordinate
YMAX
maximum Y coordinate
ZMIN
minimum of VALUE in grid
ZMAX
maximum of VALUE in grid
MEAN
mean of value in grid (-9999 if unknown)
STDV
standard deviation of VALUE (-9999 if unknown)
NCOLS
number of columns; number of mesh points in X dimension
NROWS
number of rows; number of mesh points in Y dimension
NCLASS
number of classes (for integer grids only) (0=floating point)
TYPE
the grid type (1 for integer and 2 for floating point)
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AML Functions
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User Input Functions - GETGRID
Displays a menu of grids from which one can be selected
Usage: [GETGRID { {prompt_string}}
{-SORT I -NOSORT} {-NONE} {-OTHER}]
Arguments
I is used to identify the set of grids to
list
{prompt_string} allows a prompt to be given
-SORT is used to sort the list of choices
-NOSORT is used to turn off sorting of the list of choices
-NONE means NONE will be provided as a valid selection
-OTHER means _OTHER_ is choice and when selected, terminal
input is requested
Returned Type
string
Returned Value
The full pathname to the selected grid, or a null string if no
choice was selected
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User Input Functions - GETGRID (Continued)
Notes
&terminal must be set prior to using this function
On X-windows devices, the choices are displayed as a scrolling
list in a popup window
If none is selected, a null string is returned.
The -NOEXTENSION option does not suppress file extensions
in the returned string
Since the comment string in AML is /* and UNIX pathnames use
the forward slash, pathnames ending with a wildcard character
should be quoted.
If the wild card is omitted, all grids in the current workspace
will be listed
Example:
Arc: &s grid := [getgrid * 'Select a Grid' -sort]
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AML Functions
User Input Functions - GETIMAGE
Displays a menu of images from which one can be selected
Usage: [GETIMAGE { {<-image_type}
{prompt.string}} {-SORT I -NOSORT} {-NONE} {-OTHER}}!
Arguments
I is used to identify the set of grids to
list
<-image_type> indicates the image type to display. Valid
choices are:
-EXT, -ALL, -ADRG, -BIL, -BIP, -BSQ, -ERDAS, -GRID, -
IMAGINE, -RLC, -SUNRASTER, and -TIFF
{prompt_string} allows a prompt to be given
-SORT is used to sort the list of choices
-NOSORT is used to turn off sorting of the list of choices
-NONE means NONE will be provided as a valid selection
-OTHER means _OTHER_ is choice and when selected, terminal
input is requested
Returned Type
string
Returned Value
The full pathname to the selected image, or a null string if no
choice was selected
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User Input Functions - GETIMAGE (Continued)
Notes
&terminal must be set prior to using this function
On X-windows devices, the choices are displayed as a scrolling
list in a popup window
If none is selected, a null string is returned.
-EXT is the default and returns only those image files with valid
file extensions.
Example:
Arc: &s image := [getimage * -tiff 'Select an Image' -sort]
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AML Functions
User Input Functions - GETSTACK
Displays a menu of grid stacks from which a selection can be
made
Usage: [GETSTACK { I wild_card>
{prompt_string}} {-SORT I -NOSORT} {-NONE} {-OTHER}]
Arguments
I is used to identify the grid stacks to
list
{prompt_string} allows a prompt to be given
-SORT is used to sort the list of choices
-NOSORT is used to turn off sorting of the list of choices
-NONE means NONE will be provided as a valid selection
-OTHER means _OTHER_ is choice and when selected, terminal
input is requested
Returned Type
string
Returned Value
The full pathname of the selected grid stack, or a null string is
no selection was made
Notes
^terminal must be set prior to using this function
On X-windows devices, the choices are displayed as a scrolling
list in a popup window
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User Input Functions - GETSTACK (Continued)
If none is selected, a null string is returned.
If the wild card is omitted, the tins in the current workspace are
listed
Since the comment string in AML is /* and UNIX pathnames use
the forward slash, pathnames ending with a wildcard character
should be quoted.
Example:
Arc: &s stack := [getstack * 'Select a grid stack' -sort]
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A BCDEFG H I J K L 171 NOPQRSTUVWXYZ
A B C D
E F G H I J K L f;1 N 0 P Q R S TU V W X Y Z
An alphabetical list of GRID commands
A
ABBREVIATIONS
ADDTOSTACK
AP
ARCTOOLS
ATUSAGE
B
BUILDSTA
BUILDVAT
c
CELLVALUE
CLASSSAMPLE
COMMANDS
CONVERTREMAP
COPY
COPYSTACK
turns command abbreviations on or off.
adds one or more grids to a stack.
allows entry of ARCPLOT commands directly
from the Grid: prompt.
invokes the ARC/INFO menu interface.
returns the usage for ATOOL commands.
builds a statistics file (STA) for a grid based upon
the VALUE item.
builds a value attribute table (VAT) for a grid.
returns the value and attributes for the cell
containing a specified point,
enables to interactively select training samples on
the displayed composite of stack's layers, helps to
evaluate taken samples, and saves them in a grid,
lists available GRID commands or just those
commands which begin with (prefix),
converts remap tables from INFO to ASCII files or
ASCII to INFO files.
duplicates a grid. All information associated with
the grid is duplicated.
copies a stack including its component grids to a
new stack.
CORRELATION
CREATEREMAP
D
DENDROGRAM
DESCRIBE
DRAWSIG
DRAWZONESHAPE
DROPFROMSTACK
E
EXTERNAL
EXTERNALALL
F
FILL
FORMEDIT
An alphabelical list of GRID commands
calculates the cross correlation between two input
grids and prints the correlation coefficient to the
screen.
generates a remap table for a grid.
constructs a tree diagram showing the distances
between sequentially merged classes in a
signature file.
provides a detailed description of a grid and its
contents.
displays class signatures as ellipses in a two
dimensional graph.
draws ellipses approximating the shape and
orientation of each zone.
eliminates one or more grids from a stack.
corrects external .file pathnames for a geographic
data set's INFO data files,
recursively finds all subdirectories under the
specified directory and corrects the external file
pathnames of the INFO data .files for all
geographic data sets found in all workspaces
fills sinks or levels peaks in a continuous grid to
remove small imperfections in the data,
starts the graphical form editor for AML form
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B C D E.F G H I J K L M NO P Q R S TU V W XY Z A B CDE F G H I J KL UN OP QRSTUVWXYZ
G
GEARY
GRIDCOMPOSITE
GRIDEDIT
GRIDNODATA-
SYMBOL
GRIDPAINT
GRIDQUERY
GRIDSHADES
H
HELP
HISTOGRAM
IMAGE
INDEXITEM
INFO
K
KILL
An alphabetical list of GRID commands
calculates the Geary spatial autocorrelation index
for a grid and prints it to the screen,
displays three grids as a composite image,
the grid editing command prefix,
sets the shade symbol or colormap index for
displaying grid cells with NODATA.
displays a grid using the specified item value,
stretch or remap_table and a colormap_file.
displays the set of cells in a grid that satisfy a
logical expression using the current shadeset.
shades a grid using the specified item value,
stretch, or remap table to determine color from
the current shadeset.
starts ArcDoc, the on-line documentation system
for ARC/INFO.
displays the frequency distribution of values in a
grid.
displays a raster image or a group of images from
an image catalog.
creates an attribute index to increase access speed
to the specified item during query operations
begins execution of the INFO subsystem for ARC
using the INFO subdirectory in the current user
workspace.
deletes a grid or stack.
L
LIST
LISTCOVERAGES
LISTGRIDS
LISTIMAGES
LISTSTACKS
LLSFIT
LOADCOLORMAP
LOG
M
MAKESTACK
MERGEVAT
MORAN
P
PRINT
PRINTDOC
PROJECT-
COMPARE
Q
QUIT
An alphabetical list of GRID commands
lists the item values for all records of the specified
INFO data file.
lists the coverages contained in a workspace,
lists the grids contained in a workspace,
lists the images contained in a directory,
list the stacks contained in a workspace,
performs a linear least-squares fit to a link file or
link coverage and reports the RMS error and
coefficients.
loads the colors of an ASCII colormap file into the
current shadeset.
lists the contents of a log file or add a new entry to
the log.
generates a stack from a given set of grids,
merges the value attribute tables, VATs, of two
grids.
calculates the Moran spatial autocorrelation
index for a grid and prints it to the screen.
prints the results of an expression to the screen,
invokes a menu for printing multiple ArcDoc files
sets the comparison level of the present session
stops execution of the GRID system and returns
control to the ARC system
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ABC DEF G H I J KLMNO P O R STUVWXYZ A B CD E F G H I J K L MNOPQ R S TU V W XY 2
An alphabetical list of GRID commands
R
REGRESSION outputs the regression coefficients for the
regression model in tabular form.
REMAPGRID a menu-based tool for creating custom remap
tables for a grid.
REMOVESCALAR removes or deletes a scalar variable.
RENAME changes the name of a grid.
RESET re-initializes the GRID analysis environment to
the default settings.
RESTORE restores the GRID analysis environment to the
settings stored in an environment file.
s
SAI creates an output grid containing a slope-aspect
index, or a lookup table of hypothetical solar
illumination to be used for displaying.
SAVE saves the current GRID analysis environment.
SAVECOLORMAP saves the colors corresponding to symbols in the
current shadeset to an ASCII colormap file.
SCATTERGRAM displays a graph showing in a two dimensional
space the distribution of one grid's cells' values
against another grid.
SETCELL sets the cell size of the current analysis
environment.
SETMASK sets the mask of the current analysis
environment.
SETWINDOW seta the window of the current analysis
environment.
SHADEGRID a menu-based tool for generating shade sets and
remap tables that can be used to create a custom
display of a grid.
An alphabetical list of GRID commands
SHOW lists the current setting of the User workspace,
display device, method of coordinate input, or
digitizer on your terminal screen.
STACKHISTOGRAM displays a set of histograms, ones for each layer
a stack.
displays a set of graphs, one for each pair of a
stack's layers, showing in a two dimensional
space the distribution of cell values,
displays all layers of a stack in a layout fashion
using the current shade set.
calculates the statistics for layers of a stack,
shows the status of the current GRID analysis
environment.
STACKSCATTER-
GRAM
STACKSHADE
STACKSTATS
STATUS
u
USAGE
V
VERIFY
VISDECODE
VISENCODE
returns the usage of the specified command.
sets the automatic verification of answers to
system prompts.
returns a list of observation points that can be
seen by cell locations with a specified value in the
VALUE item of the output grid from the
VISIBILITY function.
returns the VISIBLE-CODE value or values that
are assigned to each cell location on the output
grid created by the VISIBILITY function which
can be seen by up to sixteen specified points.
. Master -.
Contents..
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v:^:o^Contflms'v.!'. Back-''.'.:1':J Page .V ;j.:.Ppgซ / \.'.Pagd
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Contents
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-------
A BCD E F G H IJKLM NOPQRSTUVWXYZ
ABCDEFGH I J K L M N OPQRSTUV W X Y Z
alphabetical list of GRID functions
ABS
ACOS
ACOSH
ADJUST
AGGREGATE
ASIN
ASINH
ASPECT
ATAN
ATAN2
ATANH
B
BASIN
BLOCKMAJORITY
calculates the absolute value of the input,
calculates the inverse cosine of the input,
calculates the inverse hyperbolic cosine of the
input.
adjusts or rubber sheets a grid in either direction
along the links from a separate link coverage,
generates a reduced resolution version of a grid
where each output cell contains the MIN, MAX,
MEAN, MEDIAN, or SUM of the input cells that
are encompassed by the extent of the output cell,
calculates the inverse sine of the input,
calculates the inverse hyperbolic sine of the input,
identifies the direction of maximum rate of change
in z value from each cell,
calculates the inverse tangent of the input,
calculates the inverse tangent (based on y/x) of
the input.
calculates the inverse hyperbolic tangent of the
input.
creates a grid delineating all drainage basins
within the analysis window,
an aggregation function that partitions the input
grid into blocks and finds the majority of the
values for the specified cells (defined by the
neighborhood parameters) within the block and
An alphabetical list of GRID functions
sends it to each cell location in the block on the
output grid. -
BLOCKMAX an aggregation function that partitions the input
grid into blocks and finds the highest value for the
specified cells (defined by the neighborhood
parameters) within the block and sends it to each
cell location in the block on the output grid.
BLOCKMEAN an aggregation function that partitions the input
grid into blocks land finds the mean value for the
specified cells (defined by the neighborhood
parameters) within the block and sends it to each
cell location in the block on the output grid.
BLOCKMEDIAN an aggregation function that partitions the input
grid into blocks and finds the median value for the
specified cells (defined by the neighborhood
parameters) within the block and sends it to each
cell location in the block on the output grid.
BLOCKMIN an aggregation function that partitions the input
grid into blocks and finds the smallest value for
the specified cells (defined by the neighborhood
parameters) within the block and sends it to each
cell location in the block on the output grid.
BLOCKRANGE an aggregation function that partitions the input
grid into blocks and finds them range of values for
the specified cells (defined by the neighborhood
parameters) within the block and sends it to each
cell location in the block on the output grid.
BLOCKSTD an aggregation function that partitions the input
grid into blocks and finds the standard deviation
of values for the specified cells (defined by the
neighborhood parameters) within the block and
sends it to each cell location in the block on the
output grid.
B C D E F G HI J KL MNOPQRSTUVW X Y Z
A BCOtF G H I J K L M N O P Q R S T U V W X Y Z
BLOCKSUM
BLOCKVARIETY
BOUNDARYCLEAN
c
CEIL
CLASSPROB
CLASSSIG
COLOR2BLUE
COLOR2GREEN
COLOR2HUE
An alphabetical list of GRID functions
an aggregation function that partitions the input
grid into blocks and finds the sum of values for the
specified cells (defined by the neighborhood
parameters) within the block and sends it to each
cell location in the block on the output grid,
an aggregation function that partitions the input
grid into blocks and finds the variety of the values
(the number of different values) for the specified
cells (defined by the neighborhood parameters)
within the block and sends it to each cell location
in the block on the output grid,
smooths the boundary between zones by
expanding and shrinking the boundary.
returns the next highest whole value that is
greater than or equal to the input values.
creates a stack of probability layers for each class
represented in the signature file.
creates an ASCII signature file that contains
signatures of classes, defined as class samples in
the input grid, in the input stack
converts a grid and associated colormap into a
grid representing the RGB blue components of the
input.
converts a grid and associated colormap into a
grid representing the RGB green components of
the input.
converts a grid and associated colormap into a
grid representing the HSV hue components of the
input.
COLOR2RED
COLOR2SAT
COLOR2VAL
COMBINE
CON
CORRIDOR
COS
COSH
COSTALLOCATION
COSTBACKLINK
COSTDISTANCE
COSTPATH
An alphabetical list of GRID functions
converts a grid and associated colormap into a
grid representing the RGB red components of the
input.
converts a grid and associated colormap into a
grid representing the HSV saturation components
of the input.
converts a grid and associated colormap into a
grid representing the HSV value components of
the input.
combines multiple grids on a cell-by-cell basis,
such that a unique output value is assigned to
each unique combination of input values,
performs one or more conditional ltfelse
evaluations.
records for each cell location the sum of tne
accumulative costs for two input accumulative-
cost grids.
calculates the cosine of the input,
calculates the hyperbolic cosine of the input,
identifies for each cell the zone of each source cell
that could be reached with the least accumulative
cost.
defines the neighbor that is the next cell on the
least-accumulative-cost path from a cell to a set of
source cells.
calculates for each cell the least-accumulative-
cost distance over a cost surface to a source cell or
a set of source cells.
produces an output grid that records the least-cost
path(s) from selected cell(s) in the input
, or from interactive selection on
the display, to the closest source cell defined
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-------
A B C D E F G H I J KLMNOPO RSTUVWXYZ
ABCDEFGH IJ K L M N O PQRSTUVWXYZ
CURVATURE
D
DARCYFLOW
E
EDITSIG
EQUALTO
EUCALLOCATION
EUCDIRECTION
EUCDISTANCE
EXP
EXP 10
EXP2
EXPAND
An alphabetical list of GRID functions
within the in terms of cost
distance.
calculates the curvature of a surface at each cell
center.
calculates the groundwater volume balance
residual for steady state flow in an aquifer and
the seepage velocity for each cell using Darcy*s
Law.
edits a signature file by merging, renumbering
and deleting class signatures and creates a new
signature file.
evaluates, on a cell-by-cell basis, the number of
times in an argument list that the input grid
values are equal to the value specified by the first
argument.
calculates for each cell the zone of the closest
source cell (in Euclidean distance),
calculates the direction in degrees that each cell
center is from the cell center of the closest source.
The output values are based on compass
directions, with 0" being reserved for the source
cells.
calculates for each cell the Euclidean distance to
the closest source.
calculates the basee exponential of the input,
calculates the baselO exponential of the input,
calculates the base2 exponential of the input,
expands the selected zones by a specified number
of cells.
F
FLIP
FLOAT
FLOOR
FLOWACCUM-
ULATION
FLOWDIRECTION
FLOWLENGTH
FMOD
FOCALFLOW
FOCALMAJORITY
FOCALMAX
FOCALMEAN
FOCALMEDIAN
An alphabetical list of GRID functions
flips a grid along a horizontal axis.
converts integer values to floating-point values.
returns the greatest integer value that is smaller
than or equal to the input values.
creates a grid of accumulated flow to each cell,
by accumulating the weight for fill cells that flow
into each downslope cell.
creates a grid of flow direction from each cell to its
steepest downslope neighbor,
calculates distance, or weighted distance along a
flow path.
divides the values of the first input by the second
input and returns the remainder on a cell-by-cell
basis.
determines the flow of the values in the input grid
within each cell's immediate neighborhood,
for each cell location on an input grid, finds the
'majority* value (the value that appears most
often) within a specified neighborhood and sends
it to the corresponding cell location on the output
grid.
for each cell location on an input grid, finds the
highest value within a specified neighborhood and
sends it to the corresponding cell location on the
output grid.
for each cell location on an input grid, finds the
mean of the values within a specified
neighborhood and sends it to the corresponding
cell location on the output grid,
for each cell location on an input grid, finds the
median value within a specified neighborhood and
ABCDEFGH I J KLMNOP QRSTUVWXYZ
An alphabetical list of GRID functions
sends it to the corresponding cell location on the
output grid.
for each cell location on an input grid, finds the
minimum value within a specified neighborhood,
and sends it to the corresponding cell location on
the output grid.
for each cell location on an input grid, finds the
range of the values within a specified
neighborhood and sends it to the corresponding
cell location on the output grid,
for each cell location on an input grid, finds the
standard deviation of the values within a specified
neighborhood and sends it to the corresponding
cell location on the output grid,
for each cell location on an input grid, adds the
values within a specified neighborhood and sends
the sum to the corresponding cell location on the
output grid.
for each cell location on an input grid, determines
the number of unique values (or the variety)
within a specified neighborhood and sends it to
the corresponding cell location on the output grid.
FOCALMIN
FOCALRANGE
FOCALSTD
FOCALSUM
FOCALVARIETY
G
GREATERTHAN
GRIDLINE
GRSDPOINT
GRIDPOLY
evaluates, on a cell-by-cell basis, the number of
times in an argument list that the input grid
values are greater than the value specified by the
first argument.
converts a grid representing rasterized linear
features to a line coverage.
converts a grid representing raster point features
into a point coverage.
converts a grid to a polygon coverage.
H
HILLSHADE
HSV2BLUE
HSV2GREEN
HSV2RED
IDW
INT
ISNULL
ISOCLUSTER
K
KRIGING
An alphabetical list of GRID functions
creates a shaded relief grid from a grid by
considering the sun illumination angle and
shadows.
converts three grids representing the hue,
saturation, and value of an HSV color model to a
blue grid for an RGB color model,
converts three grids representing the hue,
saturation, and value of an HSV color model to a
green grid for an RGB color model,
converts three grids representing the hue,
saturation, and value of an HSV color model to a
red grid for an RGB color model
performs an inverse distance weighted
interpolation on a point data set.
converts input floating-point values to integer
values through truncation.
returns '1' if the input value is NODATA, and '0' if
it is not.
uses an isodata clustering algorithm to determine
the characteristics of the natural groupings of
cells in a multi-dimensional space, and stores the
results in an ASCII signature file.
interpolates a point data set into a surface using
knging.
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Contents ContentsBack . ,. Page' P*ge Page' ฆ' ฆ ฆ
-------
ABC 0 E F G HI J KIM NO P 0 R S TU V W X Y Z
ABCDEFGH IJ KLM NO P Q R S TU V W X Y Z
An alphabetical list of GRID functions
L
LESSTHAN evaluates, on a cell-by-cell basis, the number of
times in an argument list that the input grid
values are less than the value specified by the first
argument.
LINEGRID creates a grid from line features in a coverage.
LN calculates the natural logarithm (basee) of the
input.
LOGIO calculates the base 10 logarithm of the input.
LOG2 calculates the base2 logarithm of the input.
. LPOS determines, on a cell-by-oell basis, the position of
the input grid with the minimum value in the
argument list.
M
MAJORITY uses multiple input grids to determine the
'majority* value (the value that appears most
often) on a cell-by-cell basis.
MAJORITYFILTER replaces cells in a grid based upon the majority of
their contiguous neighboring cells.
MAX uses multiple input grids to determine the
maximum value on a cell-by-cell basis.
MEAN uses multiple input grids to determine the mean
value on a cell-by-cell basis.
MED uses multiple input grids to determine the median
value on a cell-by-cell basis.
MERGE merges multiple, possibly nonadjacent input grids
into a single grid based upon order of input.
MIN uses multiple input grids to determine the
minimum value on a cell-by-cell basis.
MINORITY uses multiple input grids to determine the
'minority' value (the value that appears least
often) on a cell-by-cell basis.
Master /.First "^Previous'-Ivi'Next :;v:- Print;..'Viev/er i;:;.VQult:;:
Coซttonis//^:^i::ฃ;ฃContent^
B C D E F G H I J KLM NOPQRSTUVW X Y 2
MIRROR
MLCLASSIFY
MOSAIC
N
NIBBLE
NORMAL
PARTICLETRACK
PATHDISTANCE
PICK
POINTGRID
POLYGRID
POPULARITY
POROUSPUFF
An alphabetical list of GRID (unctions
mirrors a grid along a vertical axis,
performs maximum likelihood classification on a
stack and creates the classification grid,
creates one grid out of many adjacent grids and
makes a smooth transition over the overlapping
areas of the neighboring grids
replaces areas in a grid corresponding to a mask,
with the values of the nearest neighbors,
creates a grid with randomly dispersed values of a
normal distribution.
calculates the path of a particle through a velocity
field.
calculates, for each cell, the least-accumulative-
cost distance over a cost surface from a source cell
or a set of source cells while accounting for surface
distance and horizontal and vertical cost factors,
using the values of an input grid, determines
which expression will be used, and uses it to
compute the output values,
creates a grid from points in a coverage,
creates a grid from polygons in a coverage,
determines the value in an argument list that is
at a certain level of popularity on a cell-by-cell
basis within the analysis window. The particular
level of popularity (the number of occurrences of
each value) is specified by the first argument,
calculates the time-dependent, two-dimensional
concentration distribution of a solute, introduced
10
ASCO EF GH I J K L M N 0 P Q R S TU V W X Y Z
POW
PRINCOMP
PROJECT
R
RAND
RANK
RECLA.SS
REGIONGROUP
RESAMPLE
RGB2HUE
RGB2SAT
RGB2VAL
ROTATE
An alphabetical list of GRID functions
instantaneously at a discrete point into a
vertically mixed aquifer.
calculates the nth power of the input.
generates a stack of layers being the principal
components of the input stack
projects coordinates between two projections for a
grid.
generates a random number between '0' and '1'.
returns the value in the th position in the
rank order of the argument list, which is created
using the specified multiple input grids, on a cell-
by-cell basis.
reclassifies (or changes) the value of the input
cells using a remap table on a cell-by-cell basis,
records for each cell in the output the identity of
the connected region to which it belongs A unique
number is assigned to each region
changes the cell size of a grid,
converts three grids representing the red, green,
and blue of an RGB color model to a hue grid for
an HSV color model.
converts three grids representing the red, green,
and blue of an RGB color model to a saturation
grid for an HSV color model,
converts three grids representing the red, green,
and blue of an RGB color model to a value grid for
an HSV color model.
rotates a grid around the lower left corner by a
specified angle.
s
SAMPLE
SAMPLESIG
SCALAR
SELECT
SELECTBOX
SELECTCIRCLE
SELECTMASK
SELECTPOINT
SELECTPOLYGON
SETNULL
SHIFT
SHRINK
SIN
SINH
An alphabetical list of GRID functions
lists the values of a group of cells from one or
more grids.
creates an ASCII signature file that contains a set
of statistics defining zones specified in the input
file.
returns the result of a map algebra expression
involving numbers as a numeric value that can be
assigned to a scalar variable.
based on the evaluation of the
, selects cell values from the
input grid on a cell-by-cell basis.
selects cells from the input grid that are either
inside or outside a specified box.
selects cells from the input grid that are either
inside or outside a specified circle.
masks (or sets to NODATA) all cell locations in
the first input grid that have been assigned
NODATA in the second input grid.
selects cells from the input grid that are either
inside or outside the boundary of the cell within
which a selected point falls.
selects cells from the input grid that are either
inside or outside a polygon
returns NODATA if the evaluation of the input
condition is TRUE', if it 'FALSE', returns the
value specified by the second input argument.
shifts the coordinates of a grid, and optionally
changes the cell size.
shrinks the selected zones by a specified number
of cells.
calculates the sine of the input,
calculates the hyperbolic sine of the input.
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-------
ABCDEF6 H I J K L MN0P0:RSTUVWXY2
A B CDEFGH I J K L M N 0 P Q R S T.U V W X Y Z
SINK
SLICE
SLOPE
SNAPPOUR
SPLINE
SQR
SQRT
STREAMLINE
STREAMUNK
STREAMOROER
T
TAN
TANH
TEST
THIN
TREND
An alphabetical list of GRID functions
creates a grid identifying all sinks, or areas of
internal drainage.
'slices' (or changes) a range of values of the input
cells by specified ranges, zones of equal area, or
zones with equal intervals',
identifies the rate of maximum change in z value
from each cell.
snaps selected pour points to the cell of highest
flow accumulation within a specified
neighborhood.
performs a spline interpolation on a point data set
resulting in a smoothed surface with the
minimum curvature.
calculates the square of the input.
calculates the square root of the input.
converts a grid representing a raster linear
network to a line coverage.
assigns unique values to sections of a raster linear
network between intersections.
assigns a numeric order to segments of a grid
representing branches of a linear network.
calculates the tangent of the input,
calculates the hyperbolic tangent of the input,
uses a Boolean evaluation of the
to test the cell values from
the input grid and to set the output to '1' or *0' on a
cell-by-cell basis.
thins raster linear features by reducing the
number of pixels representing the width of the
features.
performs a trend interpolation on a point data set.
u
UPOS
V
VARIETY
VISIBILITY
w
WARP
WATERSHED
ZONALAREA
ZONALCENTROID
ZONALFILL
ZONALGEOMETRY
ZONALMAJORITY
An alphabetical list of GRID functions
determines, on a cell-by-cell basis, the position of,
the input grid with the maximum value in the
argument list.
uses multiple input grids to determine the variety
of the values (the number of unique values) on a
cell-by-cell basis.
performs visibility analysis on a grid by
determining how many observation points can be
seen from each cell location of the input grid, or
which cell locations can be seen by each
observation point.
rubber sheets a grid along a set of links using a
polynomial transformation,
determines the contributing area above a set of
cells in a grid.
calculates the area of each zone in the input grid,
creates a grid with cells locating the geometric
centers of each zone of an input grid,
fills zones using the minimum cell value from a
weight grid, along the zone boundary,
calculates for each zone of the input grid its area,
perimeter, thickness, and the characteristics of
ellipse and records them in the output INFO file
records in each output cell the majority value (the
value that appears most often) of all cells in the
13
14
A B C D E F G H I J K L M N O P Q R S TU V W X Y Z
An alphabetical list of GRID functions
that belongs to the same zone as the
output cell. Zones are identified by the values of
the cells in the input .
records in each output cell the maximum value of
all cells in the that belong to the
same zone as the output cell. Zones are identified
by the values of the cells in the input .
records in each output cell the mean of the values
of all cells in the that belong to the
same zone as the output cell. Zones are identified
by the values of the cells in the input
records in each output cell the median value of all
cells in the that belongs to the same
zone as the output cell. Zones are identified by the
values of the cells in the input .
records in each output cell the minimum value of
all cells in the that belong to the
same zone as the output cell. Zones are identified
by the values of the cells in the input .
calculates the perimeter of each zone in the input
grid.
records in each output cell the range of values of
all cells in the that belong to the
same zone as the output cell. Zones are identified
by the values of the cells in the input
records in an output INFO table the minimum,
maximum, range, sum, mean, standard deviation
and variety of the values of all cells in the
that belong to the same zone. Zones
are identified by the values of the cells in the
input .
records in each output cell the standard deviation
of the values of all cells in the that
ZONALMAX
ZONALMEAN
ZONALMEDIAN
ZONALMIN
ZONALPERIMETER
ZONALRANGE
ZONALSTATS
ZONALSTD
A BCOEFG H I J K L M N 0 P Q RSTUVWXY Z
An alphabetical list of GRID functions
belong to the same zone as the output cell. Zones
are identified by the values of the cells in the
input .
records in each output cell the sum of the values
of all cells in the that belong to the
same zone as the output cell. Zones are identified
by the values of the cells in the input .
calculates for each zone on an input grid the
deepest or thickest point within the zone from its
surrounding cells.
records in each output cell the variety of values
(the number of unique values) of all cells in the
that belong to the same zone as the
output cell. Zones are identified by the values of
the cells in the input .
ZONALSUM
ZONALTHICKNESS
ZONALVARIETY
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-------
An alphabetical list of GRID operators
alphabetical list of GRID operators
I performs a Boolean-exclusive-OR operation on
two inputs.
!! performs a bitwise-exclusive-OR operation on the
binary values of two inputs.
& performs a Boolean-AND operation on two inputs.
&& performs a bitwise-AND operation on the binary
values of two inputs.
* multiplies the values of two inputs.
*= multiplies the values of a grid on a cell-by-cell
basis within a DOCELL block and assigns the
results to a scalar variable.
+ adds the values of two inputs.
+= adds the values of a grid on a cell-by-cell basis
within a DOCELL block and assigns the results to
a scalar variable.
subtracts the values of the second input from the
values of the first input.
-= subtracts the values of a grid on a cell-by-cell
basis within a DOCELL block and assigns the
results to a scalar variable.
/= divides the values of a grid on a cell-by-cell basis
within a DOCELL block and assigns the results to
a scalar variable.
:= creates a temporary output grid from an
expression within a DOCELL block.
< performs a relational-less-than operation on two
inputs.
ซ performs a bitwise-left-shift operation on the
binary value of an input.
<= performs a relational-less-than-or-equal-to
operation on two inputs.
= creates a new output grid from an input
expression.
== performs a relational-equal-to operation on two
inputs.
> performs a relational-greater-than operation on
two inputs.
ป performs a bitwise-right-shift operation on the
binary value of an input.
>= performs a relational-greater-than-or-equal-to
operation on two inputs.
CAND performs a combinatorial-AND operation on two
input grids.
COR performs a combinatorial-OR operation on two
input grids.
CXOR performs a combinatorial-exclusive-OR operation
on two input grids.
DIFF determines which values from the first input are
logically different from the values of the second
input.
DIV divides the values of two inputs.
IN determines which values from the first input are
contained in the .
MOD divides the values of the first input by the values
of the second input and returns the remainder.
OVER returns those values from the first input that are
nonzero; otherwise, returns the value from the
second input.
UNARY- changes the sign of the input (multiplies by -1).
A performs a Boolean-complement operation on an
input.
An alphabetical list of GRID operators
** performs a bitwise-complement operation on the
binary value of an input.
*= performs a relational-not-equal-to operation on
two inputs.
{= determines the minimum value of a grid within a
DOCELL block and assigns the result to a scalar
variable.
I performs a Boolean-OR operation on two inputs.
II performs a bitwise-OR operation on the binary
values of two inputs.
}= determines the maximum value of a grid within a
DOCELL block and assigns the result to a scalar
variable.
-------
An alphabetical list of GRID statements
DOCELL controls per-cell processing on a cell-by-cell basis.
IF performs a conditional iffelse evaluation on a cell-
by-cell basis.
WHILE repeats a statement list body as long as the tested
condition is a semi-Boolean TRUE value
(nonzero).
1
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:
-------
A functional list of GRID commands
.A functional list of GRID commands
Accumulative operators
Arithmetic operators
Assignment operators
Bitwise operators
Block (unctions
Boolean operators
Color model conversion
Combinatorial lunctions
Combinatorial operators
Conditional statements
Data cleanup functions
Data conversion
Distance functions
Editing commands
Exponential and logarithmic functions
Focal functions
Geometric transformation
Grid display
GRID management commands
Hydrologic functions
Logical operators
Miscellaneous functions
Reclassification functions
Relational operators
Selection functions
Shape analysis functions
Statistical functions and commands
Surface functions and commands
Trigonometric functions
Visibility tools
Zonal functions
(MORE)
A functional list of GRID commands
A functional list of GRID commands
Arithmetic operators
multiplies the values of two inputs.
+ adds the values of two inputs.
subtracts the values of the second input from the
values of the first input.
DIV divides the values of two inputs.
MOD divides the values of the first input by the values
of the second input and returns the remainder.
UNARY - changes the sign of the input (multiplies by -1).
Boolean operators
! performs a Boolean-exclusive-OR operation on
two inputs.
& performs a Boolean-AND operation on two inputs.
A performs a Boolean-complement operation on an
input.
I performs a Boolean-OR operation on two inputs.
Relational operators
< performs a relational-less-than operation on two
inputs.
<= performs a relational-less-than-or-equal-to
operation on two inputs.
== performs a relational-equal-to operation on two
inputs.
> performs a relational-greater-than operation on
two inputs.
>= performs a relational-greater-than-or-equal-to
operation on two inputs.
*= performs a relational-not-equal-to operation on
two inputs.
Bitwise operators
'! performs a bitwise-exclusive-OR operation on the
binary values of two inputs.
&& performs a bitwise-AND operation on the binary
values of two inputs.
ซ performs a bitwise-left-shift operation on the
binary value of an input.
ป performs a bitwise-right-shift operation on the
binary value of an input.
^ performs a bitwise-complement operation on the
binary value of an input.
II performs a bitwise-OR operation on the binary
values of two inputs.
Combinatorial operators
CAND performs a combmatonal-AND operation on two
input grids.
COR performs a combinatonal-OR operation on two
input grids.
CXOR performs a combinatonal-exclusive-OR operation
on two input grids.
Logical operators
D1FF determines which values from the first input are
logically different from the values of the second
input.
IN determines which values from the first input are
contained in the .
OVER returns those values from the first input that are
nonzero; otherwise, returns the value from the
second input.
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A functional list of GRID commands
A functional list of GRID commands
)=
Accumulative operators
multiplies the values of a grid on a cell-by-cell
basis within a DOCELL block and assigns the
results to a scalar variable,
adds the values of a grid on a cell-by-cell basis
within a DOCELL block and assigns the results to
a scalar variable.
subtracts the values of a grid on a cell-by-cell
basis within a DOCELL block and assigns the
results to a scalar variable,
divides the values of a grid on a cell-by-cell basis
within a DOCELL block and assigns the results to
a scalar variable.
determines the minimum value of a grid within a
DOCELL block and assigns the result to a scalar
variable.
determines the minimum value of a grid within a
DOCELL block and assigns the result to a scalar
variable.
Assignment operators
= creates a new output grid from an input
expression.
:= creates a temporary output grid from an
expression within a DOCELL block.
Trigonometric functions
ACOS calculates the inverse cosine of the input.
ACOSH calculates the inverse hyperbolic cosine of the
input.
AS IN calculates the inverse sine of the input.
ASINH calculates the inverse hyperbolic sine of the input.
ATAN calculates the inverse tangent of the input.
ATAN2
ATANH
COS
COSH
SIN
SINH
TAN
TANH
EXP
EXP10
EXP2
LN
LOG 10
LOG 2
POW
SQR
SORT
calculates the
the input,
calculates the
input.
calculates the
calculates the
calculates the
calculates the
calculates the
calculates the
inverse tangent (based on y/x) of
inverse hyperbolic tangent of the
cosine of the input,
hyperbolic cosine of the input,
sine of the input,
hyperbolic sine of the input,
tangent of the input,
hyperbolic tangent of the input.
AGGREGATE
CONVERTREMAP
CREATEREMAP
RECLASS
Exponential and logarithmic functions
calculates the basee exponential of the input,
calculates the baselO exponential of the input,
calculates the base2 exponential of the input,
calculates the natural logarithm (basee) of the
input.
calculates the baselO logarithm of the input,
calculates the base2 logarithm of the input,
calculates the nth power of the input,
calculates the square of the input,
calculates the square root of the input.
Reclassification functions
generates a reduced resolution version of a grid
where each output cell contains the MIN, MAX,
MEAN, MEDIAN or SUM of the input cells that
are encompassed by the extent of the output cell,
converts remap tables from INFO to ASCII files or
ASCn to INFO files,
generates a remap table for a grid,
reclassifies (or changes) the value of the input
cells using a remap table on a cell-by-cell basis.
A functional list of GRID commands
A functional list of GRID commands
REMAPGRID a menu-based tool for creating custom remap
tables for a grid.
SLICE 'slices' (or changes) a range of values of the input
cells by specified ranges, zones of equal area, or
zones with equal intervals.
Selection functions
SELECT based on the evaluation of the
, selects cell values from the
input grid on a cell-by-cell basis.
SELECTBOX selects cells from the input grid that are either
inside or outside a specified box.
SELECTCIRCLE selects cells from the input grid that are either
inside or outside a specified circle.
SELECTMASK masks (or sets to NODATA) all cell locations in
the first input grid that have been assigned
NODATA in the second input grid.
SELECTPOINT selects cells from the input grid that are either
inside or outside the boundary of the cell within
which a selected point falls.
SELECTPOLYGON selects cells from the input grid that are either
inside or outside a polygon.
TEST uses a Boolean evaluation of the
to test the cell values from
the input grid and to set the output to '1' or '0' on a
cell-by-cell basis.
Statistical functions and commands
CLASSPROB creates a stack of probability layers for each class
represented in the signature file.
CLASSSAMPLE enables to interactively select training samples on
the displayed composite of stack's layers, helps to
evaluate taken samples, and saves them in a grid.
CLASSSIG
CORRELATION
DENDROGRAM
EDITSIG
EQUALTO
GEARY
GREATERTHAN
ISOCLUSTER
LESSTHAN
LPOS
creates an ASCII signature file that contains
signatures of classes, defined as class samples in
the input grid, in the input stack.
calculates the cross correlation between two input
grids and prints the correlation coefficient to the
screen.
constructs a tree diagram showing the distances
between sequentially merged classes in a
signature file.
edits a signature file by merging, renumbering
and deleting class signatures and creates a new
signature file.
evaluates, on a cell-by-cell basis, the number of
times in an argument list that the input grid
values are equal'to the value specified by the first
argument.
calculates the Geary spatial autocorrelation index
for a grid and prints it to the screen,
evaluates, on a cell-by-cell basis, the number of
times in an argument list that the input grid
values are greater than the value specified by the
first argument.
uses an isodata clustering algorithm to determine
the characteristics of the natural groupings of
cells in a multi-dimensional space, and stores the
results in an ASCII signature file,
evaluates, on a cell-by-cell basis, the number of
times in an argument list that the input grid
values are less than the value specified by the first
argument.
determines, on a cell-by-cell basis, the position of
the input grid with the minimum value in the
argument list.
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-------
A functional list of GRID commands
A functional list of GRID commands
MAJORITY uses multiple input grids to determine the
'majority' value (the value that appears most
often) on a cell-by-cell basis.
MAX uses multiple input grids to determine the
maximum value on a cell-by-cell basis.
MEAN uses multiple input grids to determine the mean
value on a cell-by-cell basis.
MED uses multiple input grids to determine the median
value on a cell-by-cell basis.
MIN uses multiple input grids to determine the
minimum value on a cell-'by-cell basis.
MINORITY uses multiple input grids to determine the
'minority1 value (the value that appears least
often) on a cell-by-cell basis.
MLCLASSIFY performs maximum likelihood classification on a
stack and creates the classification grid.
MORAN calculates the Moran spatial autocorrelation
index for a grid and prints it to the screen.
POPULARITY determines the value in an argument list that is
at a certain level of popularity on a cell-by-cell
basis within the analysis window. The particular
level of popularity (the number of occurrences of
each value) is specified by the first argument.
PRINCOMP generates a stack of layers being the principal
components of the input stack
RANK returns the value in the th position in the
rank order of the argument list, which is created
using the specified multiple input grids, on a cell-
by-cell basis.
REGRESSION outputs the regression coefficients for the
regression model in tabular form.
SAMPLESIG creates an ASCII signature file that contains a set
of statistics defining zones specified in the input
file.
STACKSTATS calculates the statistics for layers of a stack.
UPOS determines, on a cell-by-cell basis, the position of
the input grid with the maximum value in the
argument list.
VARIETY uses multiple input grids to determine the variety
of the values (the number of unique values) on a
cell-by-cell basis.
Miscellaneous functions
ABS calculates the absolute value of the input.
CEIL returns the next highest whole value that is
greater than or equal to the input values.
CON performs one or more conditional if/else
evaluations.
FLOAT converts integer values to floating-point values.
FLOOR returns the greatest integer value that is smaller
than or equal to the input values.
FMOD divides the values of the first input by the second
input and returns the remainder on a cell-by-cell
basis.
INT converts input floating-point values to integer
values through truncation.
ISNULL returns '1' if the input value is NODATA, and '0' if
it is not.
MERGE merges multiple, possibly nod-adjacent input
grids into a single grid based upon order of input.
MOSAIC merges multiple adjacent continuous grids and
performs interpolation in the overlapping areas
NORMAL creates a grid with randomly dispersed values of a
normal distribution.
PICK using the values of an input grid, determines
which expression will be used, and uses it to
compute the output values.
RAND generates a random number between '0' and '1'.
10
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A functional list of GRID commands
A functional list of GRID commands
SAMPLE lists the values of a group of cells from one or
more grids.
SCALAR returns the result of a map algebra expression
involving numbers as a numeric value that can be
assigned to a scalar variable.
SETNULL returns NODATA if the evaluation of the input
condition is TRUE'; if it 'FALSE', returns the
value specified by the second input argument.
Focal functions
FOCALFLOW determines the flow of the values in the input grid
within each cell's immediate neighborhood.
FOCALMAJORITY for each cell location on an input grid, finds the
'majority' value (the value that appears most
often) within a specified neighborhood and sends
it to the corresponding cell location on the output
grid.
FOCALMAX for each cell location on an input grid, finds the
highest value within a specified neighborhood and
sends it to the corresponding cell location on the
output grid.
FOCALMEAN for each cell location on an input grid, finds the
mean of the values within a specified
neighborhood and sends it to the corresponding
cell location on the output grid.
FOCALMEDIAN for each cell location on an input grid, finds the
median value within a specified neighborhood and
sends it to the corresponding cell location on the
output grid.
FOCALMIN for each cell location on an input grid, finds the
minimum value within a specified neighborhood,
and sends it to the corresponding cell location on
the output grid.
FOCALRANGE for each cell location on an input grid, finds the
range of the values within a specified
neighborhood and sends it to the corresponding
cell location on the output grid.
FOCALSTD for each cell location on an input grid, finds the
standard deviation of the values within a specified
neighborhood and sends it to the corresponding
cell location on the output grid
FOCALSUM for each cell location on an input grid, adds the
values within a specified neighborhood and sends
the sum to the corresponding cell location on the
output grid.
FOCALVARIETY for each cell location on an input gnd, determines
the number of unique values (or the variety)
within a specified neighborhood and sends it to
the corresponding cell location on the output grid
Zonal (unctions
ZONALAREA calculates the area of each zone in the input grid.
ZONALCENTROID creates a grid with cells locating the geometric
centers of each zone of an input gnd
ZONALFILL fills zones using the minimum cell value from a
weight gnd, along the zone boundary.
ZONALGEOMETRY records in an output INFO table the area,
perimeter and thickness of the values of all cells
m an input grid that belong to the same zone.
ZCh ALMAJORIT Y records in each output cell the majority value (the
value that appears most often) of all cells in the
that belongs to the same zone as the
output cell. Zones are identified by the values of
the cells in the input .
ZONALMAX records in each output cell the max mi urn value of
all cells in the cvalue_grid> that belong to the
11
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-------
A functional list of GRID commands
A functional list of GRID commands
same zone as the output cell. Zones are identified
by the values of the cells in the input .
ZONALMEAN records in each output cell the mean of the values
of all cells in the that belong to the
same zone as the output cell. Zones are identified
by the values of the cells in the input .
ZONALMEDIAN records in each output cell the median value of all
cells in the that belongs to the same
zone as the output cell. Zones are identified by the
values of the cells in the input .
ZONALMIN records in each output dell the minimum value of
all cells in the that belong to the
same zone as the output cell. Zones are identified
by the values of the cells in the input .
ZONALPERIMETER calculates the perimeter of each zone in the input
grid.
ZONALRANGE records in each output cell the range of values of
all cells in the that belong to the
same zone as the output cell. Zones are identified
by the values of the cells in the input .
ZONALSTATS records in an output INFO table the minimum,
maximum, range, sum, mean, standard deviation
and variety of the values of all cells in the
that belong to the same zone. Zones
are identified by the values of the cells in the
input .
ZONALSTD records in each output cell the standard deviation
of the values of all cells in the that
belong to the same zone as the output cell. Zones
are identified by the values of the cells in the
input .
ZONALSUM records in each output cell the sum of the values
of all cells in the that belong to the
same zone as the output cell. Zones are identified
by the values of the cells in the input czone_grid>.
13
ZONALTHICKNESS calculates for each zone on an input grid the
deepest or thickest point within the zone from its|
surrounding cells.
ZONALVARIETY records in each output cell the variety of values
(the number of unique values) of all cells in the
that belong to the same zone as the
output cell. Zones are identified by the values of
the cells in the input .
Block functions
BLOCKMAJORITY an aggregation function that partitions the input
grid into blocks and finds the majority of the
values for the specified cells (defined by the
neighborhood parameters) within the block and
sends it to each cell location in the block on the
output grid.
BLOCKMAX an aggregation function that partitions the input
grid into blocks and finds the highest value for the
specified cells (defined by the neighborhood
parameters) within the block and sends it to each
cell location in the block on the output grid.
BLOCKJ/EAN an aggregation function that partitions the input
grid into blocks and finds the mean value for the
specified cells (defined by the neighborhood
parameters) within the block and sends it to each
cell location in the block on the output grid.
BLOCKMEDIAN an aggregation function that partitions the input
grid into blocks and finds the median value for the
specified cells (defined by the neighborhood
parameters) within the block and sends it to each
cell location in the block on the output grid.
BLOCKMIN an aggregation function that partitions the input
grid into blocks and finds the smallest value for
the specified cells (defined by the neighborhood
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A functional list of GRID commands
A functional list of GRID commands
parameters) within the block and sends it to each COSTBACKLINK
cell location in the block on the output grid.
BLOCKRANGE an aggregation function that partitions the input
grid into blocks and finds them range of values for COSTDISTANCE
the specified cells (defined by the neighborhood
parameters) within the block and sends it to each
cell location in the block on the output grid. COSTPATH
BLOCKSTD an aggregation function that partitions the input
grid into blocks and finds the standard deviation
of values for the specified cells (defined by the
neighborhood parameters) within the block and
sends it to each cell location in the block on the
output grid. EUCALLOCATION
BLOCKSUM an aggregation function that partitions the input
grid into blocks and finds the sum of values for the EUCDIRECTION
specified cells (defined by the neighborhood
parameters) within the block and sends it to each
cell location in the block on the output grid.
BlOCKVARiETY an aggregation function that partitions the input
grid into blocks and finds the variety of the values EUCDISTANCE
(the number of different values) for the specified
cells (defined by the neighborhood parameters) PATHDISTANCE
within the block and sends it to each cell location
in the block on the output grid.
Distance functions
CORRIDOR records for each cell location the sum of the
accumulative costs for two input accumulative- COMBINE
cost grids.
COSTALLOCATION identifies for each cell the zone of each source cell
that could be reached with the least accumulative
cost.
DOCELL
defines the neighbor that is the next cell on the
least-accumulative-cost path from a cell to a set of
source cells.
calculates for each cell the least-accumulative-
cost distance over a cost surface to a source cell or
a set of source cells.
produces an output grid that records the least-cost
path(s) from selected celKs) in the input
, or from interactive selection on
the display, to the closest source cell defined
within the in terms of cost
distance.
calculates for each cell the zone of the closest
source cell (in Euclidean distance),
calculates the direction in degrees that each cell
center is from the cell center of the closest source.
The output values are based on compass
directions, with 0* being reserved for the source
cells.
calculates for each cell the Euclidean distance to
the closest source.
calculates, for each cell, the least-accumulative-
cost distance over a cost surface from a source cell
or a set of source cells while accounting for surface
distance and horizontal and vertical cost factors
Combinatorial functions
combines multiple grids on a cell-by-cell basis,
such that a unique output value is assigned to
each unique combination of input values
Conditional statements
controls per-cell processing on a cell-by-cell basis
Master ln
-------
A functional list of GRID commands
A functional list of GRID commands
IF performs a conditional ltfelse evaluation on a cell-
by-cell basis.
WHILE repeats a statement list body as long as the tested
condition is a semi-Boolean TRUE value
(nonzero).
GRID management commands
ABBREVIATIONS turns command abbreviations on or off.
ADDTOSTACK adds one or more grids to a stack.
AP allows entry of ARCPLOT commands directly
from the Grid: prompt.
ARCTOOLS invokes the ARC/INFO menu interface.
ATUSAGE returns the usage for ATOOL commands.
BU1LDSTA builds a statistics file (STA) for a grid based upon,
the VALUE item.
BUILDVAT builds a value attribute table (VAT) for a grid.
COMMANDS lists available GRID commands or just those
commands which begin with (prefix).
COPY duplicates a grid. All information associated with
the grid is duplicated.
COPYSTACK copies a stack including its component grids to a
new stack.
DESCRIBE provides a detailed description of a grid and its
contents.
DROPFROMSTACK eliminates one or more grids from a Btack.
EXTERNAL corrects external file pathnames for a geographic
data set's INFO data files.
EXTERNAL-ALL recursively finds all subdirectories under the
specified directory and corrects the external file
pathnames of the INFO data files for all
geographic data sets found in all workspaces.
FORMEDIT starts the graphical form editor for AML form
INDEX ITEM
INFO
KILL
LIST
LISTCOVERAGES
LISTGRIDS
L1STIMAGES,
LISTSTACKS
LOG
MAKESTACK
MERGEVAT
PRINT
PROJECT-
COMPARE
QUIT
REMOVESCALAR
RENAME
RESET
RESTORE
SAVE
SETCELL
SETMASK
creates an attribute index to increase access speed
to the specified item during query operations,
begins execution of the INFO subsystem for ARC
using the INFO subdirectory in the current user
workspace,
deletes a grid.
lists the item values for all records of the specified
INFO data file.
, lists the coverages contained in a workspace
lists the grids contained in a workspace,
lists the images contained in a workspace and,
optionally, their type.
lists the stacks contained in the workspace,
lists the contents of a log file or add a new entry to
the log.
generates a stack from a given set of grids,
merges the value attribute tables, VATs, of two
grids.
prints the results of an expression to the screen
sets the comparison level of the present session.
stops execution of the GRID system and returns
control to the ARC system.
removes or deletes a scalar variable.
changes the name of a grid.
re-initializes the GRID analysis environment to
the default settings.
restores the GRID analysis environment to the
settings stored in an environment file,
saves the current GRID analysis environment,
sets the cell size of the current analysis
environment.
sets the mask of the current analysis
environment.
1? 18
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A functional list of GRID commands A functional list of GRID commands
sETWINDOW sets the window of the current analysis
environment.
SHOW lists the current setting of the user workspace,
display device, method of coordinate input, or
digitizer on your terminal screen.
STATUS shows the status of the current GRID analysis
environment.
USAGE returns the usage of the specified command
VERIFY sets the automatic verification of answers to
system prompts.
Geometric transformation
In ARC
CONTROLPOINTS
GRIDDESKEW
ADJUST
FLIP
LLSFIT
MIRROR
PROJECT
RESAMPLE
initiates an interactive program that allows the
user to create a link file by graphically choosing
from and to points. Also allows the user to
interactively evaluate the goodness of fit of
different polynomial transformations for the
selected links.
corrects common distortions in scanned
documents.
In GRID
adjusts or rubber sheets a grid in either direction
along the links from a separate link coverage.
flips a grid along a horizontal axis.
performs a linear least-squares fit to a link file or
link coverage and reports the RMS error and
coefficients.
mirrors a grid along a vertical axis
projects coordinates between two projections for a
grid.
changes the cellsize of a grid.
ROTATE rotates a grid around the lower left comer by a
specified angle.
SHIFT shifts the coordinates of a grid, and optionally
changes the cell size.
WARP rubber sheets a grid along a set of links using a
polynomial transformation.
Color model conversion
COLOF12BLUE converts a grid and associated colormap into a
grid representing the RGB blue components of the
input.
COLOR2GREEN converts a grid and associated colormap into a
grid representing the RGB green components of
the input.
COLOR2HUE converts a grid and associated colormap into a
grid representing the HSV hue components of the
input.
COLOR2RED converts a grid and associated colormap into a
grid representing the RGB red components of the
input
COLOR2SAT converts a grid and associated colormap into a
grid representing the HSV saturation components
of the input.
COLOR2VAL converts a grid and associated colormap into a
grid representing the HSV value components of
the input.
HSV2BLUE converts three grids representing the hue,
saturation, and value of an HSV color model to a
blue grid for an RGB color model
HSV2GREEN converts three grids representing the hue,
saturation, and value of an HSV color model to a
green grid for an RGB color model.
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A functional list of GRID commands
A functional list of GRID commands
HSV2RED converts three grids representing the hue,
saturation, and value of an HSV color model to a
red grid for an RGB color model.
RGB2HUE converts three grids representing the red, green,
and blue of an RGB color model to a hue grid for
an HSV color model.
RGB2SAT converts three grids representing the red, green,
and blue of an RGB color model to a saturation
grid for an HSV color model.
RGB2VAL converts three grids representing the red, green,
and blue of an RGB color'model to a value grid for
an HSV color model.
Surface functions and commands
In ARC
TOPOGRID generates a digital elevation model from
coverages of elevation.
TOPOGR1DTOOL menu driven interface for the TOPOGRID
command.
In GRID
ASPECT identifies the direction of maximum rate of change
in z value from each cell.
CURVATURE calculates the curvature of a surface at each cell
center.
HILLSHADE creates a shaded relief grid from a grid by
considering the sun illumination angle and
shadows.
IDW performs an inverse distance weighted
interpolation on a point data set.
KRIGING interpolates a point data set into a surface using
kriging.
21
SAI creates an output grid containing a slope-aspect
index, or a lookup table of hypothetical solar
illumination to be used for displaying such a grid
SLOPE identifies the rate of maximum change in z value -
from each cell.
SPLINE performs a spline interpolation on a point data set
resulting in a smoothed surface with the
minimum curvature.
TREND performs a trend interpolation on a point data set.
Shape analysis functions
EXPAND expands the selected zones by a specified number
of cells.
REGIONGROUP records for each cell in the output the identity of
the connected region to which it belongs. A unique
number is assigned to each region.
SHRINK shrinks the selected zones by a specified number
of cells.
Editing commands
BRUSH changes cell values in a manner similar to
stroking on paint with a paintbrush.
COLORS specifies how to draw the grid.
DRAW displays images and grids specified in the current
draw environment.
DrawBox draws a box on the grid.
DrawCircte draws a circle on the grid.
DRAWING sets the draw environment for the edit grid.
DrawLine draws a line on the grid.
DrawPolygon draws a polygon on the grid.
EDIT specifies the name of the grid to edit.
ENHANCE applies an enhancing filter to the selected area.
FillBox fills a box on the grid.
FillCEII changes the value of an individual cell on the grid.
22
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A functional list of GRID commands
A functional list of GRID commands
FillCircle fills a circle on the grid.
FillPolygon fills a polygon on the grid.
FillRegion changes the value of a connected group of cells.
FillType specifies how cell values are assigned to filled
areas.
FillValue sets the cell value for filling areas and drawing
lines.
FilterSizo sets the neighborhood size for the enhancement
filters.
FLIP flips the selected area along a horizontal axis.
GET copies the selected area from another grid into the
current edit grid.
GndMErge merges the specified grids into the current edit
grid.
IMAGE displays an image or a group of images from an
image catalog.
UneWidth sets the width for drawing lines.
MIRROR mirrors the selected area along a vertical axis
MOVE moves the selected area.
OOPS undoes changes made to the edit grid
OOPSOFF disables the oops environment.
OOPSON activates the oops environment.
PREForences sets the editing preference for operations that
change the orientation or position of the selected
area.
PUT copies the selected area into another edit grid.
QUIT terminates the current grid editing session.
RegionRemove eliminates raster features whose cell count falls
between a threshold minimum and maximum
value.
RegionSample sets the threshold minimum and maximum cell
counts for eliminating raster features.
REMAP applies a contrast stretch to enhance grid display
RemoveEdit removes edit grids from the current editing
session
23
ROTATE rotates the selected area.
SAVE saves changes made to an edit grid.
SELectAII selects the entire grid.
SELectBox selects all cells contained by a box
SELectCircle selects all cells contained by a circle.
SELectCLear clears the selected area.
SELeclPolygon selects all cells contained by a polygon.
SMOOTH applies a smoothing filter to the current selected
area.
SPecKleRemove eliminates noise within the selected area.
SPecKleSize sets the size of speckles to remove.
Data cleanup functions
BOUNDARYCLEAN smooths the boundary between zones by
expanding and shrinking the boundary.
MAJORITYFILTER replaces cells in a grid based upon the majority of
their contiguous neighboring cells.
NIBBLE replaces areas in a grid corresponding to a mask,
with the values of the nearest neighbors.
THIN thins rasterized linear features by reducing the
number of pixels representing the width of the
features.
Hydrologic functions
BASIN creates a grid delineating all drainage basins
within the analysis window.
DARCYFLOW calculates the groundwater volume balance
residual for steady state flow in an aquifer and
the seepage velocity for each cell using Darcy's
Law.
FILL fills sinks or levels peaks in a continuous grid to
remove small imperfections in the data.
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A functional list of GRID commands
A functional list of GRID commands
FLOWACCUM- creates a grid of accumulated flow to each cell,
ULATION by accumulating the weight for all cells that flow
into each downslope cell.
-LOWDi RECTI ON creates a grid of flow direction from each cell to its
steepest downslope neighbor.
FLOWLENGTH calculates distance, or weighted distance along a
flow path.
PARTICLETRACK calculates the path of a particle through a velocity
field.
POROUSPUFF calculates the time-dependent, two-dimensional
concentration distribution of a solute, introduced
instantaneously at a discrete point into a
vertically mixed aquifer.
SINK creates a grid identifying all sinks, or areas of
internal drainage.
SNAPPOUR snaps selected pour points to the cell of highest
flow accumulation within a specified
neighborhood.
STREAMLINE converts a grid representing a raster linear
network to a line coverage.
STREAMLINK assigns unique values to sections of a raster linear
network between intersections.
STREAMORDER assigns a numeric order to segments of a grid
representing branches of a linear network.
WATERSHED determines the contributing area above a set of
cells in a grid.
Visibility tools
VISDECODE returns a list of observation points that can be
seen by cell locations with a specified value in the
VALUE item of the output grid from the
VISIBILITY function.
VISENCODE returns the VISIBLE-CODE value or values that
are assigned to each cell location on the output
grid created by the VISIBILITY function which
can be seen by up to sixteen specified points
VISIBILITY performs visibility analysis on a grid by
determining how many observation points can be
seen from each cell location of the input grid, or
which cell locations can be seen by each
observation point.
Data conversion
in ARC
ASCIIGRID converts an ASCII file to a grid.
ADRGGRID converts ADRG data into a grid.
DEMLATTICE converts a DEM in USGS or TAME format to a
lattice.
DTEDGRID converts a US DMA DTED file into a grid.
FLOATGRID converts a file of binary floating point numbers
into a grid.
GRIDASC1I converts a grid to an ASCII file.
GRIDFLOAT converts a cell value of a grid into a file of binary
floating point numbers.
GRIDIMAGE converts a grid into the specified output image
format.
GRIDMOSS converts a grid into a MOSS raster export file.
GRIDSVF converts a grid to an ARC/INFO single-variable
file (SVF).
IMAGEGRID converts an image into a grid or set of grids.
LATTICEDEM converts a lattice to a DEM in USGS format.
MOSSGRID converts a MOSS raster export file into a grid.
SVFGRID converts an ARC/INFO single-variable file into a
grid.
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A functional list of GRID commands
A functional list of GRID commands
In GRID
GRIDLINE converts a grid representing rasterized linear
features to a line coverage.
GRIDPOINT converts a grid representing raster point features
into a point coverage.
GRIDPOLY converts a grid to a polygon coverage.
LINEGRID creates a grid from line features in a coverage.
POINTGRID creates a grid from points in a coverage.
POLYGRID creates a grid from polygons in a coverage.
Grid display
In ARCPLOT
CELLVALUE returns the value and attributes for the cell
containing a specified point.
IMAGE displays a raster image or a group of images from
an image catalog on the screen.
GRIDCOMPOSITE displays three grids as a composite image.
GRIDDIRECTION draws arrows whose direction is determined by
the values of grid cells.
GRIDNET draws a fishnet or mesh of lines delineating the
boundary of cells in a grid, or the boundary of a
grid.
GRIDNODATA- sets the shade symbol or colormap index for
SYMBOL displaying grid cells with NODATA.
GRIDPAINT displays a grid using the item value, stretch or
lookup table, and an ASCII colormap file.
GRIDQUERY displays the set of cells in a grid that satisfy a
logical expression.
GRIDSHADES shades a grid using a symbolized or transformed
item value to determine color.
DRAWSIG
DRAWZONESHAPE
HISTOGRAM
LOADCOLORMAP
SAVECOLORMAP
SCATTERGRAM
SHADEGRID
STACKHISTOGRAM
STACKSCATTER-
GRAM
STACKSHADE
In GRID
displays class signatures as ellipses in a two
dimensional graph
draws ellipses approximating the shape and
orientation of each zone.
displays the frequency distribution of values in a
grid.
loads the colors of an ASCII colormap file into the
current shadeset.
saves the colors corresponding to symbols in the
current shadeset to an ASCII colormap file,
displays a graph showing in a two dimensional
space the distribution of one grid's cells' values
against another grid.
a menu-based tool for generating shade sets and
remap tables that can be used to create a custom
display of a grid.
displays a set of histograms, ones for each layer of
a stack.
displays a set of graphs, one for each pair of a
stack's layers, showing in a two dimensional space
the distribution of cell values
displays all layers of a stack in a layout fashion
using the current shade set.
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