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USERS GUIDE FOR THE
AERMOD TERRAIN
PREPROCESSOR (AERMAP)
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EPA-454/B-03-003
October 2004
USER'S GUIDE FOR THE
AERMOD TERRAIN PREPROCESSOR (AERMAP)
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air Quality Planning and Standards
Emissions, Monitoring, and Analysis Division
Research Triangle Park, North Carolina 27711
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NOTICE
This user's guide has been reviewed by the Office of Air Qualtiy Planning and Standards,
U.S. Environmental Protection Agency, and has been approved for publication. Mention of trade
names, products, or services does not convey, and should not be interpreted as conveying official
EPA approval, endorsement, or recommendation.
The following trademarks appear in this guide:
UNIX is a registered trademark of The Open Group
Linux is a registered trademark of Linus Torvalds
Visual Fortran is a registered trademark of Compaq Computer Corporation
Pentium is a registered trademark of Intel, Inc.
IBM is a registered trademark of International Business Machines.
Windows is a registered trademark of Microsoft Corporation.
WINZIP is a registered trademark of Nico Mak Computing, Inc.
iii
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PREFACE
The U. S. Environmental Protection Agency (EPA), in conjunction with the American
Meteorological Society (AMS), has developed a new air quality dispersion model, the
AMS/EPA Regulatory Model (AERMOD). AERMOD is a modeling system which contains: 1)
an air dispersion model, 2) a meteorological data preprocessor called AERMET, and 3) a terrain
data preprocessor called AERMAP. This user's guide focuses on the AERMAP portion of the
AERMOD modeling system.
This User's Guide for the AMS/EPA Regulatory Model Terrain Pre-processor
(AERMAP), provides technical descriptions and user instructions. Receptor and source
elevation data from AERMAP output is formatted for direct insertion into an AERMOD control
file. The elevation data are used by AERMOD when calculating air pollutant concentrations.
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ACKNOWLEDGMENTS
The User's Guide for AERMAP has been prepared by Pacific Environmental Services,
Inc., Research Triangle Park, North Carolina. This effort was funded by the U.S. Environmental
Protection Agency under Contract Numbers 68D30032 and 68D30001, with Russell F. Lee and
Warren D. Peters as Work Assignment Managers. This user's guide has been modified by Peter
Eckhoff of the U.S. Environmental Protection Agency, Research Triangle Park, North Carolina.
We are grateful to the staff of the United States Geological Survey for their helpful
suggestions and understanding of the complex relationships between the various datum standards
and their ability to convey that understanding for our programming purposes.
We also appreciate the National Geodetic Survey for posting their NADCON program to
the internet. Without NADCON, we would have had a tremendously difficult time in writing a
program to convert geographical coordinates between NAD 27 and NAD 83.
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CONTENTS
PREFACE iv
ACKNOWLEDGMENTS v
FIGURES viii
TABLES ix
1.0 INTRODUCTION 1-1
1.1 OVERVIEW 1-1
1.2 INPUT DATA REQUIREMENTS 1-2
1.3 COMPUTER HARDWARE REQUIREMENTS 1-5
2.0 OVERVIEW OF THE AERMAP TERRAIN PREPROCESSOR 2-1
2.1 BASIC CONCEPTS 2-1
2.1.1 Horizontal Datums 2-1
2.1.2 Modeling Domain 2-4
2.1.3 Sources and Receptors 2-7
2.1.4 Terrain Data Files 2-8
2.2 KEYWORD/PARAMETER APPROACH 2-10
2.3 AN EXAMPLE AERMAP INPUT FILE 2-11
2.3.1 Selecting Preprocessing Options - CO Pathway 2-12
2.3.2 Specifying a Receptor Network - RE Pathway 2-15
2.3.3 Specifying the Output File - OU Pathway 2-16
2.4 RUNNING AERMAP 2-17
2.5 SIZE LIMITATIONS AND CREATING A NEW EXECUTABLE 2-20
3.0 DETAILED KEYWORD REFERENCE 3-1
3.1 OVERVIEW 3-1
3.2 CONTROL PATHWAY INPUTS AND OPTIONS 3-2
3.2.1 Title Information 3-2
3.2.2 Options for Elevated Terrain 3-3
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3.2.3 Flagpole Receptor Height Option 3-3
3.2.4 Terrain Data Type Specifications 3-4
3.2.5 Terrain Data File Names Specifications 3-4
3.2.6 Domain Extent Specifications 3-5
3.2.7 Anchor Location Specifications 3-6
3.2.8 To Run or Not to Run - That is the Question 3-8
3.3 SOURCE PATHWAY INPUTS AND OPTIONS (OPTIONAL) 3-9
3.4 RECEPTOR PATHWAY INPUTS AND OPTIONS 3-9
3.4.1 Defining Networks of Gridded Receptors 3-10
3.4.1.1 Cartesian Grid Receptor Networks 3-10
3.4.1.2 Polar Grid Receptor Networks 3-15
3.4.2 Using Multiple Receptor Networks 3-18
3.4.3 Specifying Discrete Receptor Locations 3-19
3.4.3.1 Discrete Cartesian Receptors 3-19
3.4.3.2 Discrete Polar Receptors 3-20
3.4.3.3 Discrete Cartesian Receptors for EVALFILE Output 3-21
3 .5 OUTPUT PATHWAY INPUTS AND OPTIONS 3-22
4.0 TECHNICAL DESCRIPTION 4-1
4.1 DETERMINING RECEPTOR HEIGHT SCALES 4-1
4.2 DIGITAL ELEVATION MODEL (DEM) DATA 4-2
4.3 DATA MANIPULATION BY AERMAP 4-17
4.4 DETERMINING RECEPTOR (SOURCE) ELEVATIONS 4-18
5.0 REFERENCES 5-1
APPENDIX A. ALPHABETICAL KEYWORD REFERENCE A-l
APPENDIX B. FUNCTIONAL KEYWORD/PARAMETER REFERENCE B-l
APPENDIX C. EXPLANATION OF ERROR MESSAGE CODES C-l
C.l INTRODUCTION C-l
C.2 THE OUTPUT ERROR LOG MESSAGE SUMMARY C-l
C.3 DESCRIPTION OF THE DETAILED MESSAGE LAYOUT C-2
C.4 DETAILED DESCRIPTION OF THE ERROR/MESSAGE CODES C-4
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FIGURES
Figure Page
2-1. DEPICTION OF THE OVERLAP AND VOID AREAS AREAS CAUSED BY USING
DEM FILES WITH DIFFERENT DATUMS 2-3
2-2. RELATIONSHIP AMONG THE DEM FILES, THE DOMAIN, SOURCES AND
RECEPTORS 2-5
2-3. RELATIONSHIP OF RECEPTOR SLOPE LINE TO DEM TERRAIN NODES
AND THE DEM AND DOMAIN BOUNDARIES 2-6
2-4. EXAMPLE AERMAP OUTPUT FILE FOR THE SAMPLE PROBLEM 2-20
4-1. STRUCTURE OF A 7.5-MINUTE DEM DATA FILE 4-4
4-2. STRUCTURE OF A 1-DEGREE DEM DATA FILE 4-6
C-1. EXAMPLE OF AN AERMAP MESSAGE SUMMARY C-2
viii
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TABLES
Table Page
3-1. DATUM SWITCHES FOR ANCHOR LOCATION 3-7
4-1. DEM DATA ELEMENTS - LOGICAL RECORD TYPE A 4-7
4-2. DEM DATA ELEMENTS - LOGICAL RECORD TYPE B 4-15
B-1. DESCRIPTION OF CONTROL PATHWAY KEYWORDS B-2
B-2. DESCRIPTION OF CONTROL PATHWAY KEYWORDS AND
PARAMETERS B-3
B-3. DESCRIPTION OF SOURCE PATHWAY KEYWORDS B-5
B-4. DESCRIPTION OF SOURCE PATHWAY KEYWORDS AND PARAMETERS . . . B-6
B-5. DESCRIPTION OF RECEPTOR PATHWAY KEYWORDS B-7
B-6. DESCRIPTION OF RECEPTOR PATHWAY KEYWORDS AND
PARAMETERS B-8
B-7. DESCRIPTION OF OUTPUT PATHWAY KEYWORDS B-l 1
B-8. DESCRIPTION OF OUTPUT PATHWAY KEYWORDS AND PARAMETERS . . B-12
IX
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1.0 INTRODUCTION
The U. S. Environmental Protection Agency (EPA), in conjunction with the American
Meteorological Society (AMS), has developed a new air quality dispersion model, the
AMS/EPA Regulatory Model (AERMOD). AERMOD is designed to calculate air pollutant
concentrations in all types of terrain, from flat prairie to complex mountainous situations.
AERMOD does not process its own terrain. A preprocessor program, AERMAP, has been
developed to process this terrain data in conjunction with a layout of receptors and sources to be
used in AERMOD control files.
Terrain data is available, in the United States, from the United States Geological Survey
(USGS) and commercial sources in the form of computer terrain elevation data files. The data
have been standardized to several map scales and data formats. AERMAP has been designed to
process several of these standardized data formats. AERMAP produces terrain base elevations
for each receptor and source and a hill height scale value for each receptor. AERMAP outputs
the elevation results in a format that can be directly inserted into an AERMOD control file.
The remainder of this section provides an overall introduction to the AERMAP terrain
preprocessor including the basic input data and the hardware requirements. In Section 2, a brief
tutorial demonstrates the fundamental requirements to run AERMAP, while in Section 3, a
detailed description of each of the keywords is presented. A discussion of the technical aspects
of obtaining the hill height scale is presented in Section 4.
1.1 OVERVIEW
Regulatory dispersion models applicable for simple to complex terrain situations require
information about the surrounding terrain. With the assumption that terrain will affect air quality
concentrations at individual receptors, AERMAP first determines the base elevation at each
receptor and source. For complex terrain situations, AERMOD captures the essential physics of
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dispersion in complex terrain and therefore needs elevation data that convey the features of the
surrounding terrain. In response to this need, AERMAP searches for the terrain height and
location that has the greatest influence on dispersion for each individual receptor. This height is
the referred to as the hill height scale. Both the base elevation and hill height scale data are
produced by AERMAP as a file or files which can be directly inserted into an AERMOD input
control file.
1.2 INPUT DATA REQUIREMENTS
There are two basic types of input data that are needed to run AERMAP. First,
AERMAP requires an input runsteam file that directs the actions of AERMAP through a set of
options, and defines the receptor and source locations. The structure and syntax of an AERMAP
input runsteam file is based on the same pathways and keyword structures as in the control
runsteam files for AERMOD.
Second, AERMAP needs standardized computer files of terrain data. The data is
available in three distinct formats. There is the Digital Elevation Model (DEM) format which
follows the old USGS "Blue Book" standard (see Chapter 4.2). There is the newer Spatial Data
Transfer Standard (SDTS) which formats the DEM and other associated data in metadata form.
Finally there is the National Elevation Dataset (NED) data which is constantly updated and is
available in several formats for importing into widely used commercial software packages such
as ARCGRID, GridFloat, and BILS. Of these data formats and standards, AERMAP is
programmed to read only the USGS Blue Book format. SDTS, XYZ, and NED data has to be
converted to the Blue Book format. A SDTS and a XYZ conversion program is provided with
AERMAP. Direct input of NED data into AERMAP is being explored.
The Blue Book format has been copied directly into Chapter 4.2. It consists of an overall
header followed by terrain profiles which consist of location based sub headers and evenly
spaced terrain elevation points called nodes. Each DEM file covers a section of land based on
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latitude and longitude coordinates. These data files are obtainable through several commercial
internet sites and the USGS. Several sites, as of this writing, are offering free downloads of the
USGS's SDTS formatted DEM data files. Data in the old "native" DEM format are still
available. This note has appeared on the USGS web site as of 09 September, 2004:
http://edc.usgs.gov/geodata/
"The USGS has two options for acquiring 1:24,000-Scale (7.5-minute) Digital
Elevation Model data.
1) The original DEM 7.5 minute tiled data available only in Spatial Data Transfer
Standard (SDTS) form is available at no cost via downloads from the GeoComm
International Corporation at http://gisdatadepot.com/dem and from MapMart.com
at http://www.mapmart.com , and from Advanced Topographic Development and
Images (ATDI) at http://www.atdi-us.com. (See disclaimer).
2) The National Elevation Dataset (NED) is the result of the maturation of the
USGS effort to provide 1:24,000-scale Digital Elevation Model (DEM) data for
the conterminous U.S. and 1:63,360-scale DEM data for Alaska in a seamless
form. Available data formats include ArcGrid, Floating Point, and BILS...."
DEM data can be obtained in several different scales and horizontal data spacing
resolutions. Currently AERMAP can process both the 7.5-minute and 1-degree, Blue Book
formatted, DEM data scales with any uniform distance between nodes. AERMAP is no longer
limited to spacings of 30 meters or 3 arc-seconds, respectively. The 1-degree DEM files are
available through the Internet and via anonymous FTP from the USGS Internet site at
http://edc.usgs.gov/products/elevation.html. The 7.5-minute DEM data may be purchased from
the USGS or one of the internet sites noted above. Users should check the USGS website for the
current availability status of these data.
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There are three levels of quality for DEM data. It is recommended that Level 1 data not be used
and that Level 2 or Level 3 data be used. The level of quality has been incorporated into the
DEM main header as Data Element 3. AERMAP prints this value in its output file. The user can
view this value in the DEM file using a text editor. This value (eg. 1, 2, or 3) is found in the
main header record and has a Fortran format of 16 which begins at the 145th byte and ends at the
150th byte.
According the USGS Blue Book Data User's Guide 5, 1993: "Level 2 DEM's are
elevation data sets that have been processed or smoothed for consistency and edited to remove
identifiable systematic errors. DEM data derived from hypsographic and hydrographic data
digitizing, either photogrammetrically or from existing maps, are entered into the Level 2
category after a review on a DEM Editing System. An RMSE of one-half contour interval is the
maximum permitted. There are no errors greater than one contour interval in magnitude. The
DEM record C contains the accuracy statistics acquired during quality control." Level 3 DEM's
have a maximum permitted RMSE of one-third of the contour interval. There are no errors
greater than two-thirds contour interval in magnitude.
According the USGS Blue Book : "All 1-degree DMA Data Terrain Elevation Data Level
l's (DTED-l's) have been classified as Level 3 because the hypsographic information, when
plotted at 1:250,000 scale, is consistent with the planimetric features normally found on
1:250,000-scale topographic maps. Inconsistencies may exist, but these are regarded as isolated
cases to be tempered by the 90-percent confidence level for the overall product. NOTE: The
USGS classification of "level 3" for 1-degree DEM's is not to be confused with the DMA's
"DTED level 1." In the DMA, the term [ed. DTED] level is related to the spatial resolution of
the data and not to the source of the data."
The 1-degree DEM data are produced by the Defense Mapping Agency (DMA) in
1-degree by 1-degree units that correspond to the east or west half of 1:250,000 scale USGS
topographic quadrangle map series. These data are complete and available for the entire
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contiguous United States, Hawaii, and portions of Alaska, Puerto Rico and the Virgin Islands. A
file consists of a regular array of elevations referenced horizontally on the latitude/longitude
coordinate system of the World Geodetic System (WGS). The array consists of profiles of
terrain elevations, where a profile is a series of elevation points, or nodes, arranged from south to
north for one longitude. Each profile for the 1-degree data has a constant number of elevation
points. The horizontal spacing between each data point is 3 arc-seconds - the east-west distance
is therefore latitude dependent and corresponds to about 70 - 90 meters for the North American
continent. The elevations are expressed in meters.
1.3 COMPUTER HARDWARE REQUIREMENTS
The current revision to the AERMAP terrain preprocessor was developed on an
IBM-compatible personal computer (PC) using Compaq Visual Fortran Compiler (Version 6.6).
AERMAP has been designed to run on a PC with a Pentium class or higher central processing
unit (CPU) chip, a minimum of 64 MB of RAM, and Windows 95 or higher Windows operating
system. However, the program was written to be Fortran compliant and therefore should be
recompilable on other types of computer systems such as DOS, UNIX, or Linux-based systems.
The amount of hard disk drive storage space required for a particular application will
depend on the number and type of raw terrain (DEM) data files required to encompass the study
area. A single 7.5-minute DEM file requires about 1.1 MB of space, while a single 1-degree
DEM file requires about 10 MB of space. Additional hard disk drive space will be needed to
store 7.5 minute SDTS formatted DEM data which requires about 110KB of space per file.
SDTS data needs to be converted to the old DEM format. Each conversion of an SDTS
file produces a natively formatted DEM file of about 1.1 MB. A conversion program,
SDTS2DEM, is located on the Support Center for Regulatory Air Models web site at
http ://www. epa. gov/scram0001 as part of the AERMAP package.
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AERMAP processes a 100 km x 100 km domain which includes about 80 7.5-minute
DEM files and 360 receptors in less than 32 minutes on 733 MHz Pentium III computer.
AERMAP processes the 80 DEM files in about 5 minutes and processes the 360 receptors in
about 26.5 minutes.
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2.0 OVERVIEW OF THE AERMAP TERRAIN PREPROCESSOR
This section presents the basic concepts, including the keyword approach, of the
AERMAP preprocessor used in generating the runsteam (control) file and a short tutorial on
creating a simple AERMAP run.
2.1 BASIC CONCEPTS
AERMAP relies on the Universal Transverse Mercator (UTM) coordinate system to
identify the location of sources and receptors. This coordinate system is one method of
portraying the meridians and parallels of the earth's surface on a flat plane. The UTM system is
comprised of zones, with each zone being 6° of longitude in width. Zones are numbered from
1-60 eastward from the 180 degree International Dateline meridian at 6-degree intervals of
longitude. UTM zones 11-19 cover the contiguous United States (US DOI, 1993).
2.1.1 Horizontal Datums
The Earth is a slightly flattened sphere often referred to as an oblate ellipsoid or spheroid.
There are many mathematical methods and measurements that have been used to define the
shape of the earth (USGS,1987). The three most prevalent methods for the United States are the
Clarke 1866 spheroid, the World Geodetic Systems (WGS) of 1972 and 1984, and Geodetic
Reference System (GRS) of 1980. Projections of latitude and longitude have been placed on
each one of these spheriod/reference systems. The projections are called datums. The North
American Datum (NAD) of 1927, projected on the Clarke 1866 spheroid, was created using a
triangulation method centered on Meades Ranch, Kansas. Beginning with NAD 83 and WGS
72, the projections are Earth-centered. The NAD of 1983 is based on terrestrial and satellite data
while WGS 72 and WGS 84 are based on satellite data. NAD 83 and WGS 84 are almost
identical with no appreciable differences. For all practical purposes they are considered the
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same for AERMAP applications. Here are some common ellipsoid/reference system names and
the datums associated with them:
1. CLARKE 1866
a. NAD27 datum
b. OLD HAWAIIAN datum
c. PUERO RICAN datum
d. GUAM datum
2. GRS80/WGS84
a. NAD83 datum
b. WGS84 datum
3. WGS72
a.WGS72 datum
In layman's terms, this means that a location on Earth will have different coordinates depending
upon the datum used to define that location.
Since two or more different datums can exist for each of the two DEM scales (1-degree
and 7.5-minute) used in AERMAP, datum conversion was added to AERMAP. Datum
conversion from NAD 27 to NAD 83 is performed using the National Geodetic Survey's
NADCON software version 2.1. The main NADCON algorithms have been incorporated into
AERMAP. NADCON is designed to convert coordinates in the Continental United States
(CONUS), Old Hawaiian, Puerto Rico (and Virgin Islands), and four Alaskan datums to NAD 83
using 7 pairs of respective conversion parameter files that have LAS and LOS file extensions.
These files need to be loaded along with the AERMAP executable. These files are used to
convert receptors and sources coordinates of the old datum of the areas mentioned above to NAD
83. The files are included with the AERMAP package on the SCRAM web site,
(http://www.epa.gov/scram001 /). NADCON is used only with the 7.5-minute DEM files.
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The datum of the anchor point is enter at the end of the ANCHOR keyword statement.
For applications outside the NADCON coverage area, the user needs to enter "0". Inside one of
the areas above, the user needs to enter the number representing the datum for the ANCHOR
point. By selecting "0", no conversions will be done.
Datum conversion for the 1-degree data, from WGS 72 to GRS 80 / WGS 84, is not
performed. Differences between the datums of around 7 meters are found in the arctic near
Alaska and increase to around 17 meters in the tropics near Puerto Rico. Considering the
differences are less than the approximate 93 meters between the 1-degree nodes, the conversion
is considered inconsequential.
The difference in 7.5 minute DEM based horizontal datums can have an effect on
receptor and source elevation points. The location of a point in one datum will be different from
the location of a point under another datum (see Figure 2-1).
In DEM
On earth
files
l, dil
iff
same node
5rent locatio
DEM #4
NAD 27
coorc
ns.
A
/ \
1 \
Jinates.
DEM #5
NAD 83
DEM #6
NAD 27
1=
!!!
DEM #7
NAD 27 I
Overlap ar
\A
No DEM c<
with
r Void Area
DEM #8
NAD 27
ea between DEM files
rith two different datums
Dverage (Void) area betv\
wo different datums (eg
§1111111^:
(eg h
/een
NAD
DEM #9
NAD 27 ;
JAD 27 & i
DEM files
27 & 83)
33)
FIGURE 2-1 DEPICTION OF THE OVERLAP AND VOID AREAS CAUSED BY USING
DEM FILES WITH DIFFERENT DATUMS
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For 7.5 minute DEM files of different datums, the datum coordinate difference for a given point
in the CONUS can be close to zero in the Great Lakes region to more than 100 meters in the
Pacific Northwest and down in Florida. In Hawaii, the difference is more than 300 meters.
Since adjacent 7.5 minute DEM files have common map corners with each other (stated in
latitude and longitude), the use of DEM files with different datums can shift a map so that gaps
and overlaps occur between the adjacent DEM files as depicted in Figure 2-1. Receptors can fall
into these gaps and overlaps.
From the NADCON subroutine in AERMAP, a 7.5-minute DEM coordinate shift from
NAD27 to NAD83 is calculated for each receptor and source. The shift is applied in both
directions so that each point has coordinates under both datums. This way, if the ANCHOR
point is NAD 83, coordinates shifted to NAD 27 can be used with NAD 27 elevation files.
AERMAP then determines the single closest DEM elevation value in each quadrant to the
northwest, northeast, southeast and southwest of the receptor or source. These four elevations
are weighted by distance to the receptor to estimate an elevation for that receptor (See Section
4.4 for equations). The resulting value is the elevation that is written to file for inclusion into an
AERMOD input file. The source elevation is calculated the same way.
2.1.2 Modeling Domain
The AERMAP terrain preprocessor requires the user to define a modeling domain. A
modeling domain is defined as the area that contains all the receptors and sources being modeled
with a buffer to accommodate any significant terrain elevations. This domain can span over
multiple UTM zones and multiple adjacent DEM files provided by the user. The domain can be
specified either in the UTM or the latitude/longitude coordinate system. The preprocessor
converts the domain coordinates to the units of the DEM data, i.e., UTM when using 7.5-minute
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data and latitude/longitude when using the 1-degree data. The domain must be a quadrilateral in
the same orientation as the DEM coordinates. Figure 2-2 illustrates the relationship among the
DEM data files, the domain, and receptors.
DEM File #1
DEM File #2
Domain Boundary
Source
*
Discrete & Gridded
Receptors
DEM File #3
DEM File §4
FIGURE 2-2 RELATIONSHIP AMONG THE DEM FILES, THE DOMAIN, SOURCES AND
RECEPTORS
Significant terrain elevations include all the terrain that is at or above a 10% slope from
each and every receptor (See Chapter 4.1 for a more detailed discussion). Additional DEM files
may be needed to calculate the hill height scale for each receptor and the domain may need to be
expanded to include all significant nodes. It is up to the user to assure all such terrain nodes are
covered (See Figure 2-3).
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DEM File #1
DEM File #2
Domain Boundary
Horizontal
elevation
levels
Mandatory inclusion of DEM terrain nodes above
10% slope from each and every receptor.
Nodes must be inside Domain.
When a DEM terrain node DEM terrain nodes
breaks through the 10% excludable when
slope, additional DEM files below 10% slope
are required and the domain
needs to be expanded to
include this node.
Receptor
DEM File #3
DEM File #4
FIGURE 2-3. RELATIONSHIP OF RECEPTOR SLOPE LINE TO DEM TERRAIN NODES
AND THE DEM AND DOMAIN BOUNDARIES
During setup processing AERMAP checks all of the sources and receptors specified to
ensure that they lie within the domain and within the area covered by the DEM files. AERMAP
generates a fatal error message and will stop before calculating elevations when:
1) a receptor or source is found to lie outside the domain,
2) a receptor or source is found to lie outside of the DEM files.
If the domain extends beyond the area covered by the DEM data, further processing will
continue provided no fatal error messages are generated from the above two conditions. Smaller
domains and fewer DEM files can decrease processing time. Appropriate error messages are
produced if the domain corners do not lie within a DEM file or the receptors are outside the
DEM files.
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2.1.3 Sources and Receptors
The receptors are specified in the AERMAP terrain preprocessor in a manner identical to
the AERMOD dispersion model. AERMAP allows the user to specify discrete receptors as well
as Cartesian and polar grid networks. However, there are some special considerations for
AERMAP.
In AERMOD, when specifying discrete polar receptors, it is necessary to specify the
position of a "source" relative to which the receptor is assigned. The locations of these sources
can be specified on the optional source pathway (see Section 3.3).
All the source and receptor coordinates are referenced to a set of local coordinates which
are called ANCHOR coordinates. The ANCHOR coordinates are referenced to a set of UTM
coordinates. The datum of the referenced UTM coordinates needs to be specified on the
ANCHOR input line. This datum value will be used by the program to align the various sources
and receptors coordinates to the node coordinates of the individual DEM files. In cases where
the datums are different, the source and receptor coordinates will be shifted accordingly. A "0"
datum specification, needs to be used by international users or in the cases where the DEM files
do not have a datum stated. This will cause the program to use the coordinates as found. There
will be no shifting of coordinates due to datum differences. Fourteen conversion files for the 7.5
minute DEM data are needed if "0" is not used. These files cover coordinate shifts for the
Continental United States (CONUS), Alaska, Hawaii, Guam, Puerto Rico and the Virgin Island.
The modeling domain can cross UTM zones. However, if the receptor locations are
specified in UTM coordinates, then they must all be referenced to the same UTM zone. When
using 7.5-minute DEM data, AERMAP will check for zone changes in the receptor network, and
adjust the coordinates accordingly.
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The user has the option of having AERMAP determine the terrain or base elevations for
the receptors from the DEM data or to provide the receptor elevations. This option is set in the
COntrol pathway. If the user requests AERMAP to determine the receptor base elevations from
the DEM file(s) and provides the receptor elevations as well, the program will ignore the user
input elevations. AERMAP determines the receptor elevation of each of the receptors by a
distance-weighted two-dimensional interpolation of the elevation values at the four nearest DEM
nodes surrounding the receptor location (See section Section 4.4 for equations.). The same
procedure is applied to source elevations if source locations are identified.
If the user provides the receptor elevations, AERMAP will use these elevations rather
than extracting them from the digital data. Note that the DEM files are required even if the user
is providing the receptor heights because the DEM data are used to obtain the hill height scale
for each receptor. If the user specifies the receptor elevations, they can be entered in either feet,
meters, or decimeters. The output receptor elevations will always be in meters. If the user
indicates that receptor heights are provided but does not have the receptor heights in the input
file, then a height of 0 meters is written to the output file and a warning message will be
generated.
2.1.4 Terrain Data Files
The appropriate 7.5-minute and 1-degree DEM file(s) can be obtained from the USGS or
from commercial sites on the internet. If more than one DEM file is required, then each DEM
file specified in the input runstream must have at least one other DEM file adjacent to it
otherwise the isolated DEM file(s) will be flagged. AERMAP prints to the output file an array
of DEM files and lets the user know that a DEM file is missing from the array by stating "No
Map Present" in place of a DEM map name. This makes it easier for the user to troubleshoot for
misspelled DEM map names, errant or missing DEM files.
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When designing a study and planning to download the required terrain data, keep several
things in mind. A 1-degree DEM file or a 7.5 minute DEM file (with node spacing of 10
meters), can be as large as 10 MB. AERMAP creates an additional temporary binary file
corresponding to each DEM file which can also be as much as 6 Mb each in size, depending on
the size of the domain. A 7.5-minute DEM file, with 30 meter node spacing, can be as large as
1.2 MB but only covers l/64th of the same area as a 1-degree DEM file. Approximately 80 to 90
7.5-minute DEM files are needed for a study outward to 50 kilometers from a source.
The new Spatial Data Transfer Standard (SDTS) is being promoted by the USGS to
eventually replace the old "native" DEM files. The SDTS files are available on the internet and
can be found zipped in a "tar" format. Each SDTS file contains over a dozen files that are used
to reconstitute the SDTS data back into the old "native" DEM format. The "native" format is
read directly by AERMAP. To reconstitute a DEM file: 1) unzip the SDTS file, 2) un-"tar" the
files, 3) use SDTS2DEM to convert the SDTS files back to the native DEM format. A batch file,
DEMFILZ.BAT, was constructed and is available on the EPA web site, SCRAM, for
reconstituting DEM files. The DEMFILZ is not fully automatic and requires some responses to
batch file prompts. Detailed information and instructions are part of DEMFILZ batch file
coding.
The USGS offered DEM data files are in a UNIX-compressed format and must be
uncompressed with a utility that can work with UNIX files. These programs are widely
available as shareware and freeware programs. One example is the WINZIP program from
Nico Mak Computing, Inc. The uncompressed file does not include record delimiters that are
recognized by the Windows Operating System, and therefore may not be used directly with
AERMAP. For Windows users only, the utility program CRLF.EXE, included with AERMAP,
adds a carriage return and line feed to the end of each record in the uncompressed DEM data file
to create a DOS-compatible file. To use this utility, start the Command Prompt and simply type
CRLF followed by the input file name and output file name (without the DOS redirection
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symbols, "<", The output file is now ready to use in AERMAP. This process is for files
that are already in the old "native" DEM format.
2.2 KEYWORD/PARAMETER APPROACH
The input runsteam file needed to run the AERMAP preprocessor is based on an
approach that uses descriptive keywords and parameters, and allows for a flexible structure and
format. A brief overview of the approach is provided here. A complete description of this
approach can be found in the AERMOD User's Guide (EPA, 1998).
The input runsteam file is divided into four functional "pathways." These pathways are
identified by two-character identifiers at the beginning of each record in the runsteam. The
pathways for AERMAP are:
CO - for specifying overall job COntrol options;
SO - for specifying the SOurce location information (optional);
RE - for specifying the REceptor information; and
OU - for specifying the OUtput file information.
The optional source pathway may be used to specify source locations for the purpose of
extracting source elevations from the DEM data and/or for specifying the origin of discrete or
gridded polar receptors.
Each line, or image, in the input runsteam consists of a pathway identifier, an eight-
character keyword and a parameter list. The keywords and parameters that make up an input
runstream file can be thought of as a command language through which the user communicates
with the preprocessor what is to be accomplished for a particular run. The keywords specify the
type of option or input/output data and the parameters following the keyword define the specific
options or actual file names.
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There are several rules of syntax for structuring an input runstream. Briefly, they are:
1) All inputs for a particular pathway must be contiguous;
2) Each record in the runstream file must be 132 characters or less, which includes
the pathway, the keyword and any parameters;
3) Alphabetic characters can be input as either upper or lower case because
AERMAP converts all character input to upper case internally (except for the title
parameters and filenames);
4) Several keywords are mandatory and must be present in every runstream file;
5) With a few exceptions, the order of the keywords is not critical;
6) Blank lines can be used to improve readability; asterisks in the first two columns
(the pathway field) identify the record as a comment.
2.3 AN EXAMPLE AERMAP INPUT FILE
This section describes the three required pathways that constitute an AERMAP input file
the control (CO) pathway, the receptor (RE) pathway, and the output (OU) pathway. The
optional source (SO) pathway is described in Section 3.3.
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2.3.1 Selecting Preprocessing Options - CO Pathway
The mandatory keywords for the CO pathway are listed below. These keywords
primarily control file types and names and the definition of the modeling domain. A complete
discussion of all keywords is in Section 3 and a listing of all keywords is provided in Appendix
B.
STARTING -
Indicates the beginning of inputs for the pathway; this keyword is
mandatory on each of the pathways.
TITLEONE -
A user-specified title line (up to 68 characters) that will appear on
each page of the printed output file (an optional second title line is
also available with the keyword TITLETWO).
DATATYPE
specifies the type of raw terrain data being supplied to the
preprocessor.
DATAFILE
Identifies the raw terrain files being supplied in this run.
DOMAINXY or
DOMAINLL
Defines the extent of the domain in UTM (meters) or
Lat/Long (decimal degrees).
ANCHORXY-
Defines the relationship between the user-coordinate system and
the UTM coordinate system.
RUNORNOT-
A special keyword that tells the program whether to run the full
preprocessor executions or not. If the user selects not to run, then
the input runstream file will be processed and any input errors
reported, but no calculations will be made.
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FINISHED - Indicates that the user is finished with the inputs for this pathway;
this keyword is also mandatory on the other pathways.
The order of the keywords within this pathway is not critical, although the intent of the
input runstream file may be easier to decipher if a consistent and logical order is followed. It is
suggested that users follow the order in which the keywords are presented in Section 3, unless
there is a clear advantage to doing otherwise.
A minimal but complete runstream file for the CO pathway may look something like this:
CO
STARTING
TITLEONE
A Simple Example Problem for the AERMAP Preprocessor
DATATYPE
DEMI
DATAFILE
CHATT-W.DEM
DOMAINXY
620000.0 3920000.0 16 625000.0 3925000.0 16
ANCHORXY
0.0 0.0 622500 3922500 16 1
RUNORNOT
RUN
CO
FINISHED
The first and last keywords identify the beginning and end of the COntrol pathway. The
TITLEONE keyword provides a means of entering information about the run that will be
included as a comment card in the output file. The parameter field for the TITLEONE keyword
should not be in quotation marks. The preprocessor reads whatever appears in columns 13-80
of the TITLEONE record as the title field, without changing the lower case to upper case letters.
Leading blanks are therefore significant if the user wishes to center the title within the field.
Similar rules apply to the optional TITLETWO keyword.
In the current version, two types of raw terrain DATATYPE are allowed the
7.5-minute and 1-degree DEM data. In this example, 1-degree DEM data is being used, which is
identified by the parameter DEMI. The extent of the domain can be specified in one of two
ways DOMAINXY or DOMAINLL depending on whether the user specifies the domain
extent in UTM coordinates (DOMAINXY) or longitude/latitude coordinates (DOMAINLL). In
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this example, UTM coordinates are specified, with the southwest corner of the domain at 620000
Easting (E) and 3920000 Northing (N) in zone 16, while the northeast corner of the domain is at
625000 E and 3925000 N in zone 16. NOTE: Since longitude increases from east to west over
North America, the domain is defined by the southeast and northwest corners when DOMAINLL
is used.
The ANCHORXY keyword specifies the relationship between the coordinate system
employed by the user to define source and receptor locations and the UTM coordinate system.
The data provided on the ANCHORXY keyword are used to convert the source and receptor
locations to UTM coordinates by AERMAP. If the UTM coordinate system is used for receptor
locations, then the x- and y-coordinates for the point used to anchor the two systems are the
same. In this example, the origin of a user-specified system (0.0, 0.0) is anchored to a point with
UTM coordinates of 622500E, 3922500N in Zone 16. The entered datum value is 1 which
indicates the anchor point is referenec to NAD 27.
The only remaining mandatory keyword for the CO pathway is RUNORNOT. If the user
is unsure about the syntax or operation of keywords or parameters, or is setting up a complex
runstream file to run for the first time, it may be useful to set the preprocessor NOT to run. With
this parameter set, AERMAP simply reads and analyzes the entire input file and reports any
errors or warning messages that are generated. All of the inputs are summarized in the output
file for the user to review just as if the parameter was set to RUN. Once the input file has been
debugged using these descriptive error/warning messages, then the RUNORNOT switch can be
set to RUN, as is done in this example.
Since the pathway ID is required to begin in column 1 (see Section 2.4.8 of the
AERMOD user's guide for a discussion of this restriction), the preprocessor will assume that the
previous pathway is in effect if the pathway field is left blank, as has been done in this example
for all runstream images between the STARTING and FINISHED keywords. The preprocessor
will do the same for blank keyword fields, which will be illustrated in the next section.
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In addition to these mandatory keywords on the CO pathway, the user may select
optional keywords to specify whether or not receptor terrain elevations need to be generated or
whether they are supplied (the default is to generate terrain elevations) and to allow the use of
receptor heights above ground-level for flagpole receptors. These options are described in more
detail in Section 3.
2.3.2 Specifying a Receptor Network - RE Pathway
In this section, our example will illustrate the use of a single polar receptor network
centered on the origin of the user-specified coordinate system, perhaps the stack location. Other
options available on the REceptor pathway include specifying a Cartesian grid receptor network,
and specifying discrete receptor locations in either a polar or a Cartesian system. These other
options are described in more detail in Section 3.
For this example, a polar network with receptors located at five downwind distances for
every 10-degree flow vector around a source is specified. The RE pathway for this example is:
RE
STARTING
GRIDPOLR
POL1
STA
POL1
ORIG
0.0
0.0
POL1
DIST
100.
200.
300. 500. 1000.
POL1
GDIR
36
10.
10.
POL1
END
RE
FINISHED
The GRIDPOLR keyword can be thought of as a "sub-pathway," in that all of the
information for a particular polar network must be in contiguous records. Note, too, that there is
a set of secondary keywords, including something that looks like a STArting and ENDing that
identify the start and end of the sub-pathway. The order of secondary keywords within the
sub-pathway is not critical, similar to the primary pathways. Each image in this sub-pathway
must be identified with a network ID (up to eight alphanumeric characters), in this case it is
"POL 1." The "POL 1" coordinates are referenced back to the ANCHOR point. Multiple
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networks may be specified in a single preprocessor run. The preprocessor waits until the END
secondary keyword is encountered before processing begins. Other secondary keywords that
may be used include terrain heights for receptors on elevated terrain or flagpole receptor heights
if those options are being exercised by the user. The use of these optional secondary keywords is
described in detail in Section 3.4.
For this example, the ORIG secondary keyword specifies the location of the origin, in
(X,Y) coordinates, for the polar network being defined. The ORIG keyword is optional, and the
program will default to an origin of (0.0, 0.0) if it is omitted. This is with respect to the
ANCHOR coordinates. The DIST keyword identifies the distances in meters along each
direction radial (flow vector) at which the receptors are located. In this example, there are five
distances. More receptors could be added by adding values to the input image or by repeating
the DIST secondary keyword with the additional distances. The GDIR keyword specifies that
the program will Generate DIRection radials for the network. In this example, there are 36
directions, beginning with the 10-degree flow vector (the first parameter) and incrementing
every 10 degrees clockwise (the last parameter). As a result, there are 36 directions * 5
distances, or 180 receptors for this example. Rather than let AERMAP generate the direction
radials, the user may elect to define Discrete DIRection radials instead by using the DDIR
keyword in place of the GDIR keyword (see Section 3.4.1.2).
2.3.3 Specifying the Output File - OU Pathway
The RECEPTOR keyword on the output pathway is used to specify the output filename
for the receptor data generated by AERMAP. For this example, the output pathway may look
like this:
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OU STARTING
RECEPTOR AERMAP.OUT
OU FINISHED
where AERMAP.OUT is the name of the file that will contain the receptor data, including
receptor elevations and height scales, generated by AERMAP. The AERMAP.OUT file may
then be included in a runstream for the AERMOD model. If the optional source pathway is used
to specify source locations and terrain elevations are extracted from the DEM data, then the
output filename for the source location data would be specified using the SOURCLOC keyword
on the OU pathway (see Section 3.5).
2.4 RUNNING AERMAP
Now that we have a complete and error-free runstream input file, we are ready to run the
preprocessor and review the results. The PC-executable file for AERMAP available on the
EPA's Support Center for Regulatory Air Models (SCRAM) website on the Internet
(www.epa.gov/scram001) opens the runstream input and output message files without the need
to "redirect" the I/O on the command line using the DOS redirection symbols '<' and '>'. The
command line to run the sample problem might look something like this on the PC:
C:\> AERMAP
AERMAP assumes that the input runstream input file is named AERMAP.INP. AERMAP.OUT
is opened as the output message file containing an echo of the input runstream and a listing of
any warning or error messages generated by AERMAP. As described in Section 2.3.3, the
filename for the data file containing the terrain elevations and height scales for all of the
receptors is specified within the input runstream on the output pathway. The DOS prompt is
represented by the characters "C:\>", but may appear different on different machines, depending
on how the user configures his/her system. The important points are that the AERMAP
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executable file must be in the directory from which you are attempting to run the program. The
input file must be located in the directory from which the program is being executed. The output
file is written to the directory from which the program is being executed. Also needed are the 7
*.LAS and the 7 *.LOS files that are needed by the NADCON subroutine for converting the 7.5-
minute datums to NAD 83. These 14 files need to be in the same subdirectory as the AERMAP
executable.
When AERMAP is executed, an update on the status of processing is displayed on the PC
monitor. AERMAP first indicates that the setup information in the input runstream file is being
processed, followed by initializing the terrain data, and then displays the receptor number
currently being processed. If the preprocessor stops after completing the setup processing, then
either the RUNORNOT parameter was set to NOT, or a fatal error was encountered during the
setup processing. The user should review the message file (AERMAP.OUT in this example) to
determine why AERMAP was unsuccessful, correct the input and rerun AERMAP.
Any error message generated by the operating system rather than AERMAP is displayed
on the screen and not written to the message file. One such message might be that there is
insufficient memory available to run the program. Handling of system error messages may
require some knowledge of user's operating ssytem whether it be Windows, Unix, Linux, DOS,
MAC, etc. Sometimes the meaning of the message is obvious. Sometimes they can be obscure.
The message file specified on the command line will always be generated by the program
which will contain any error, warning or diagnostic messages that were generated during the run.
By default, the program will echo each line of the input runstream file to the message file to
provide a convenient record of the inputs as originally read into the preprocessor. However, for
some applications, the length of the input runstream file may be too cumbersome to include the
entire set of inputs at the beginning of each output file. This situation may happen, for example,
if a large number of discrete receptor locations are used. For this reason, the user is provided
with the option to "turn off the echoing of the input file at any point within the runstream file.
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This is accomplished by entering the keywords "NO ECHO" in the first two fields anywhere
within the runstream file. In other words, place NO in the pathway field, followed by a space
and then ECHO. None of the input runstream images after the NO ECHO will be echoed to the
output file. Thus, a user may choose to place NO ECHO after the Control pathway in order to
keep the control options echoed, but suppress echoing the rest of the input file.
If the original input file might be lost or destroyed, use of the NO ECHO option would
not be a wise choice. If the NO ECHO is omitted, the original runstream (input) data are echoed
to the message file. The runstream data can be copied to another filename and used as an input
file to reproduce that particular application. The data are echoed at the beginning of this file and
AERMAP keys on the "RE FINISHED" image to stop processing the runstream file.
The output data file specified on the output pathway of the input runstream contains the
receptor pathway as entered by the user in the input file with the addition of the receptor terrain
elevations (if requested) and receptor height scales as calculated by AERMAP. This output data
file can now be used for the REceptor pathway of an AERMOD input file. Several header
records are included in the output data file to identify the version of AERMAP used to generate
the file and other information useful for interpreting the results. An example of the AERMAP
output file for the sample problem is shown in Figure 2-4.
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** AERMAP - VERSION 98022
** A Simple Example Problem for the AERMAP Preprocessor
¦A* "A*
** A total of 1 1-degree DEM files were used
** DOMAINXY 620000.0 3920000.0 16 625000.0 3925000.0 16
** ANCHORXY 0.0 0.0 622500 3922500 16 1
** Terrain heights were extracted by default
ELEVUNIT
METERS
GRIDPOLR
POL1
POL1
STA
ORIG 0.0
0
. 0
POL1
DIST 100.
200.
300. 500
1000.
POL1
GDIR 36
10.
10.
GRIDPOLR
POL1
ELEV
1
465.97
451.61
426.67
416.84
535. 88
GRIDPOLR
POL1
ELEV
2
462.35
443.92
416.04
403.33
491.90
GRIDPOLR
POL1
ELEV
3
458.98
437.87
408.39
392.52
451.40
GRIDPOLR
POL1
ELEV
4
456.31
431.12
401.68
377 .89
407.62
GRIDPOLR
POL1
ELEV
5
453.52
424.67
398.19
360.74
358.05
GRIDPOLR
POL1
ELEV
6
450.14
420.11
394.95
345.67
336.48
GRIDPOLR
POL1
ELEV
7
447.18
417.53
390.88
341.64
337.38
GRIDPOLR
POL1
ELEV
8
444 .76
413.26
387.52
341.08
369.71
GRIDPOLR
POL1
ELEV
9
442.99
410.57
383.17
340.11
403.53
GRIDPOLR
POL1
HILL
1
548
. 00
547.00
547.00
536.00
539. 00
GRIDPOLR
POL1
HILL
2
548
. 00
547.00
547.00
547.00
547.00
GRIDPOLR
POL1
HILL
3
548
. 00
547 . 00
547.00
547.00
547.00
GRIDPOLR
POL1
HILL
4
548
. 00
547.00
547.00
547.00
547.00
GRIDPOLR
POL1
HILL
5
548
. 00
548.00
547.00
547.00
540.00
GRIDPOLR
POL1
HILL
6
548
. 00
548 . 00
547.00
547.00
540. 00
GRIDPOLR
POL1
HILL
7
548
. 00
548.00
548.00
547.00
548.00
GRIDPOLR
POL1
HILL
8
548
. 00
548.00
548.00
548.00
536.00
GRIDPOLR
POL1
HILL
9
548
. 00
548 . 00
548.00
548.00
536. 00
GRIDPOLR POL1 END
FIGURE 2-4 EXAMPLE OF AN AERMAP OUTPUT FILE FOR THE SAMPLE PROBLEM
2.5 SIZE LIMITATIONS AND CREATING A NEW EXECUTABLE
AERMAP was rewritten using allocatable arrays. Therefore, the only limitation may be
if users want to store large number of DEM files on their hard drives.
AERMAP was written to Fortran 90 standards. A user should be able to recompile
AERMAP for different operating systems without having to change any of the underlying source
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code. See Appendix D for a listing of compiler option settings for compiling AERMAP with
Compaq Visual Fortran.
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3.0 DETAILED KEYWORD REFERENCE
This section of the AERMAP User's Guide provides a detailed reference for all of the
input keyword options for the AERMAP preprocessor. The information provided in this section
is more complete and detailed than the information provided in Section 2. Since this section is
intended to meet the needs of experienced modelers who may need to understand completely
how particular options are implemented in the preprocessor, the information for each keyword
should stand on its own. This section assumes that the reader has a basic understanding of the
keyword/parameter approach used by the AERMOD model and the AERMAP preprocessor for
specification of input options and data. Novice users should first review the contents of Section
2 or the AERMOD User's Guide in order to obtain that understanding.
3.1 OVERVIEW
The information in this section is organized by function, i.e., the keywords are grouped
by pathway, and are in a logical order based on their function within the preprocessor. The order
of keywords presented here is the same as the order used in the functional keyword reference in
Appendix B, and the Quick Reference section at the end of the volume. The syntax for each
keyword is provided, and the keyword type is specified - either mandatory or optional and either
repeatable or non-repeatable. Unless noted otherwise, there are no special requirements for the
order of keywords within each pathway, although the order in which the keywords are presented
here and in Appendix B is recommended. Any keyword which has special requirements for its
order within the pathway is so noted following the syntax and type description.
The syntax descriptions in the following sections use certain conventions. Parameters
that are in all capital letters and underlined in the syntax description are secondary keywords that
are to be entered as indicated for that keyword. Other parameters are given descriptive names to
convey the meaning of the parameter, and are listed with an initial capital letter. Many of the
parameter names used correspond to variable names used in the computer code of the
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preprocessor. Parentheses around a parameter indicate that the parameter is optional for that
keyword. The default that is taken when an optional parameter is left blank is explained in the
discussion for that keyword.
3.2 CONTROL PATHWAY INPUTS AND OPTIONS
The COntrol pathway contains the keywords that provide the overall control of the
preprocessor run. These include the specification of the terrain data, the geographic extent of the
scenario, and others that are described below. The CO pathway must be the first pathway in the
runstream input file.
3.2.1 Title Information
There are two keywords that allow the user to specify up to two lines of title information.
The title is included as comment cards in the output data file. The first keyword, TITLEONE, is
mandatory, while the second keyword, TITLETWO, is optional. The syntax and type for the
keywords are summarized below:
Syntax:
CO TITLEONE Titlel
CO TITLETWO Title2
Type:
TITLEONE - Mandatory, Non-repeatable
TITLETWO - Optional, Non-repeatable
The parameters Titlel and Title2 are character parameters of length 68, which are read as a
single field from columns 13 to 80 of the input record. The title information is taken as it
appears in the runstream file without any conversion of lower case to upper case letters. If the
TITLETWO keyword is not included in the runstream file, then the second line of the title in the
output data file will appear blank.
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3.2.2 Options for Elevated Terrain
The optional TERRHGTS keyword controls whether the receptor elevations and optional
source elevations should be extracted from the DEM data files or that the user-provided receptor
terrain elevations should be used. The syntax and type of the TERRHGTS keyword are
summarized below:
Syntax:
CO TERRHGTS EXTRACT or PROVIDED
Type:
Optional, Non-repeatable
where the EXTRACT secondary keyword instructs the preprocessor to determine the terrain
heights from the DEM data files provided by the user. The PROVIDED secondary keyword
forces the preprocessor to use the user-specified elevations that are entered on the receptor
pathway and optional source pathway. Any terrain heights that are entered on the receptor
pathway are ignored if EXTRACT terrain option is specified, and a non-fatal warning message is
generated. The default option is to EXTRACT receptor elevations if no TERRHGTS keyword is
present in the input runstream.
3.2.3 Flagpole Receptor Height Option
The FLAGPOLE keyword specifies that receptor heights above local ground level (i.e.
flagpole receptors) are allowed on the REceptor pathway. The FLAGPOLE keyword may also
be used to specify a default flagpole receptor height other than 0.0 meters. The syntax and type
of the FLAGPOLE keyword are summarized below:
Syntax:
CO FLAGPOLE (Flagdf)
Type:
Optional, Non-repeatable
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where Flagdf is an optional parameter to specify a default flagpole receptor height. If no
parameter is provided, then a default flagpole receptor height of 0.0 meters is used. Any flagpole
receptor heights that are entered on the Receptor pathway are ignored if the FLAGPOLE
keyword is not present on the Control pathway, and a non-fatal warning message is generated.
In this case, the flagpole receptor heights are not included in the output file from AERMAP.
3.2.4 Terrain Data Type Specifications
The DATATYPE keyword is needed to specify the type of the raw terrain data being
provided to the preprocessor. The current version of AERMAP accepts either the 1-degree DEM
data or the 7.5-minute DEM data. The syntax and type of the keyword are summarized below:
Syntax:
CO DATATYPE DEMI or DEM7
Type:
Mandatory, Non-repeatable
where the secondary keyword DEMI specifies that 1-degree DEM data will be used, and DEM7
specifies that 7.5-minute DEM data will be used. Only one type of DEM data may be used in a
given AERMAP run.
3.2.5 Terrain Data File Names Specifications
The DATAFILE keyword is needed to specify the names of the raw terrain data being
provided to the preprocessor. The keyword is repeatable so that multiple raw terrain file names
can be specified. The maximum allowable number of files is determined by the NDEM
parameter in the computer code. The syntax and type of the keyword are summarized below:
Syntax: CO DATAFILE filename
Type: Mandatory, Repeatable
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If the specified file is not found on the computer, the program will generate a fatal error message.
3.2.6 Domain Extent Specifications
The DOMAINXY or the DOMAINLL keyword is used to define the geographic extent of
the domain that includes all the receptors and sources specified in this run and within which the
raw terrain data points will be included in calculation of the receptor height scales. Either of the
two keywords may be used to specify the domain extent. The DOMAINXY keyword allows the
user to specify the domain in UTM coordinates while the DOMAINLL keyword allows the user
to specify it in the World Geodetic System (latitude / longitude). The syntax and type of the
keywords are summarized below:
Syntax: CO DOMAINXY Xdmin Ydmin Zonmin Xdmax Ydmax Zonmax
CO DOMAINLL Lonmin Latmin Lonmax Latmax
Type: Mandatory, Non-repeatable
For the DOMAINXY keyword, Xdmin, Ydmin and Zonmin are the UTM Easting coordinate,
UTM Northing coordinate and the UTM zone for the lower left (southwest) corner of the
domain; Xdmax, Ydmax and Zonmax are the UTM Easting coordinate, UTM Northing
coordinate and the UTM zone for the upper right (northeast) corner of the domain. The UTM
coordinates are specified in meters. For the DOMAINLL keyword, Lonmin and Latmin are the
longitude and latitude in decimal degrees for the lower right (southeast) corner of the domain;
Lonmax and Latmax are the longitude and latitude in decimal degrees for the upper left
(northwest) corner of the domain. Note that longitude is entered first, followed by latitude. The
current version of AERMAP uses a positive value for west longitude. The DOMAIN
coordinates are not shifted for different NADs.
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3.2.7 Anchor Location Specifications
The ANCHORXY keyword is used to relate the origin of the user-specified coordinate
system in the receptor grid to the UTM coordinate system. The user has the option of specifying
the receptor locations in either UTM coordinates or in some arbitrary user-specified coordinate
system. For any further processing of the terrain data, the preprocessor needs to determine the
location of the receptors in UTM coordinates. This is done with this keyword by specifying the
coordinates of anyone geographic location in the two coordinate systems. The syntax and type
of the keyword are summarized below:
Syntax: CO ANCHORXY Xauser Yauser Xautm Yautm Zautm Nada
Type: Mandatory, Non-repeatable
where Xauser and Yauser are the coordinates of any geographic location, typically the origin
(0,0), in the user coordinate system and Xautm, Yautm and Zautm are the UTM coordinates of
the same point in UTM Easting, Northing and Zone. If the user specifies the receptor locations
in UTM coordinates, the values of Xauser and Xautm will be identical, and so will those of
Yauser and Yautm. Nada represents the horizontal datum that was used to establish the anchor
point. Nada values range from 0 to 6. All receptor and source locations are referenced to this
point.
The following is a list of applicable Nada values and the datums Nada references. These
values follow the convention used in the USGS Blue Book and the list follows the convention
used in the DEM file headers all except for the use of "0" (zero). In Table 4-1, which was
extracted from the Blue Book, also lists these codes under Data Element 27. Ellipsoid and
spheroid are often used interchangeably in the literature.
3-6
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NADA
Description
0
No conversion between NAD 27 and NAD 83 for the DEM nodes, receptors, or
sources, and for international use.
1
North American Datum of 1927 (based on Clarke 1866 ellipsoid).
Shift to NAD83 (DEM7)
2
World Geodetic System of 1972 (based on WGS 72 ellipsoid).
No shift (DEMI)
3
World Geodetic System of 1984* ("identical" to the GRS 80 ellipsoid).
No Shift (DEMI)
4
North American Datum of 1983* (based on WGS 80 ellipsoid)
No shift (DEM7)
5
Old Hawaii Datum (based on Clarke 1866 ellipsoid but not NAD 27)
Shift to NAD83 (DEM7)
6
Puerto Rico/ Virgin Island Datum (based on Clarke 1866 ellipsoid)
Shift to NAD83 (DEM7)
TABLE 3-1. DATUM SWITCHES FOR ANCHOR LOCATION
* Note: The GRS80 and WGS84 ellipsoids are considered to be the same.
Actually, there is a very small difference in the flattening which results in the
semi-minor axis, b, being different by 0.0001 meters. There is no known
application for which this difference is significant. The WGS84 and NAD83
datum are considered the same for all practical purposes.
NADCON is used to convert from NAD 27, Old Hawaiian, or Puerto Rico datums to NAD83
and vice versa.
Internal to the AERMAP model, a datum code is read from each DEM header and all 7.5
minute data are converted to NAD 83. NADCON produces the shift values in both meters and
degrees, minutes, seconds that are added to the receptor and source. NADCON is only called for
3-7
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converting 7.5-minute DEM coordinates from one datum to another. There are additional
parameter files required which have the *.LAS and *.LOS extensions for the CONUS, Hawaii,
Puerto Rico/Virgin Islands, Alaska and three Alaskan Island Groups (St. George, St. Paul, and
St. Lawrence). These 14 files need to be included in the same subdirectory as the AERMAP
input file.
Note: For international users, setting Nada to "0" will bypass NADCON and the
need to enter any parameter files.
The two 1-degree datums, WGS 72 and WGS 84, are both Earth-centric datums. The
difference in point locations varies with latitude from about 7 meters for areas north of Alaska to
about 17 meters for areas near 20 degrees north latitude. With a node spacing of approximately
90 meters, the difference between the two 1-degree datums is thought to be inconsequential. No
conversions are done between the two datum types.
3.2.8 To Run or Not to Run - That is the Question
Because of the error handling and the "defensive programming" that has been employed
in the design of the AERMAP model, it is intended that the program will read through all of the
inputs in the runstream file regardless of any errors or warnings that may be encountered. If a
fatal error occurs in processing of the runstream information, then further program calculations
will be aborted. Otherwise, the program will attempt to run. Because of the great many options
available in the AERMAP preprocessor, and the potential for wasted resources if a large run is
performed with some incorrect input data, the RUNORNOT keyword has been included on the
Control pathway to allow the user to specify whether to RUN the preprocessor and perform all of
the calculations, or NOT to run and only process the input runstream data and summarize the
setup information. The syntax and type of the RUNORNOT keyword are summarized below:
3-8
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Syntax: co runornot run or not
Type: Mandatory, Non-repeatable
3.3 SOURCE PATHWAY INPUTS AND OPTIONS (OPTIONAL)
The optional SOurce pathway is used to define source locations for the purpose of
generating source elevations from the DEM data and/or for identifying the origins of discrete
polar receptors. There is only one keyword available on the source pathway, besides
STARTING and FINISHED. The syntax and type of the LOCATION keyword are summarized
below:
Syntax:
SO LOCATION
Srcid
Srctyp Xs Ys (Zs)
Type:
Mandatory if
using
Discrete Polar Receptors,
Mandatory if
using
source ID for origin of polar grid, Repeatable
where Srcid is an alphanumeric source ID of up to eight characters, Srctyp is the source type,
which is identified by one of the secondary keywords - POINT. VOLUME. AREA.
ARE APPLY, or AREACIRC. Xs and Ys are the x-coordinate (East) and y-coordinate (North) of
the source location in meters, and Zs is the optional source elevation in meters above mean sea
level. This keyword is mandatory if any discrete polar receptors are being used or if a source ID
is used to specify the origin for a polar grid. The keyword can be repeated up to a maximum
number of sources whose value is determined by the NSRC parameter in the computer code.
3.4 RECEPTOR PATHWAY INPUTS AND OPTIONS
The REceptor pathway contains keywords that define the receptor information for a
particular run. The RE pathway contains keywords that allow the user to define Cartesian grid
receptor networks and/or polar grid receptor networks, with either uniform or non-uniform grid
spacing, as well as discrete receptor locations referenced to a Cartesian or a polar system. The
3-9
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program is initially setup to allow ten (10) gridded receptor networks of either (or both) types in
a single run, plus discrete receptors of either type, up to a maximum limit on the total number of
receptors. The limit on the total number of receptors in a given run is controlled by a Fortran
PARAMETER in the computer code (AERMAP.INC). The number of receptor networks
allowed is also controlled by a PARAMETER statement in AERMAP.INC, and may be easily
changed by the user and the program recompiled.
The default units for receptor elevations input to the AERMAP preprocessor are in
meters, however, the user may specify receptor elevations to be input in units of feet by adding
the optional RE ELEVUNIT FEET card immediately after the RE STARTING card. Regardless
of the input elevation units, AERMAP outputs all elevations in meters, and the RE ELEVUNIT
METERS card is added to the output file following the RE STARTING card.
3.4.1 Defining Networks of Gridded Receptors
Two types of receptor networks are allowed by the AERMAP preprocessor. A Cartesian
grid network, defined through the GRIDCART keyword, includes an array of points identified
by their x (east-west) and y (north-south) coordinates. A polar network, defined by the
GRIDPOLR keyword, is an array of points identified by direction and distance from a
user-defined origin. Each of these keywords has a series of secondary keywords associated with
it that are used to define the network, including any receptor elevations for elevated terrain and
flagpole receptor heights. The GRIDCART and GRIDPOLR keywords can be thought of as
"sub-pathways," since their secondary keywords include a STArt and an END card to define the
start and end of inputs for a particular network.
3.4.1.1 Cartesian Grid Receptor Networks.
Cartesian grid receptor networks are defined by use of the GRIDCART keyword. The
GRIDCART keyword may be thought of as a "sub-pathway," in that there are a series of
3-10
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secondary keywords that are used to define the start and the end of the inputs for a particular
network, and to select the options for defining the receptor locations that make up the network.
The syntax and type of the GRIDCART keyword are summarized below:
Syntax:
RE GRIDCART Netid
STA
XYINC
Xinit Xnum Xdelta Yinit
Ynum Ydelta
or
XPNTS
Gridxl Gridx2 Gridx3 ...
Gridxn, and
YPNTS
Gridyl Gridy2 Gridy3 ...
Gridyn
ELEV
Row Zelevl Zelev2 Zelev3
... Zelevn
FLAG
Row Zflagl Zflag2 Zflag3
... Z flagn
END
Type:
Optional, Repeatable
where the parameters are defined as follows:
3-11
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Netid
Receptor network identification code (up to eight alphanumeric
characters)
STA
Indicates the STArt of GRIDCART inputs for a particular network,
repeated for each new Netid
XYINC
Keyword identifying uniform grid network generated from x and y
increments
Starting x-axis grid location in meters
Number of x-axis receptors
Spacing in meters between x-axis receptors
Starting y-axis grid location in meters
Number of y-axis receptors
Spacing in meters between y-axis receptors
Xinit
Xnum
Xdelta
Yinit
Ynum
Ydelta
XPNTS
Keyword identifying grid network defined by a series of discrete x
and v coordinates (used with YPNTS)
Value of first x-coordinate for Cartesian grid (m)
Value of 'nth' x-coordinate for Cartesian grid (m)
Gridxl
Gridxn
YPNTS
Keyword identifying grid network defined by a series of discrete x
and v coordinates (used with XPNTS)
Value of first y-coordinate for Cartesian grid (m)
Value of 'nth' y-coordinate for Cartesian grid (m)
Gridyl
Gridyn
ELEV
Keyword to specify that receptor elevations follow (optional)
Indicates which row (y-coordinate fixed) is being input (Row=l
means first, i.e., southmost row)
An array of receptor terrain elevations (m) for a particular Row
(default units of meters may be changed to feet by use of RE
ELEVUNIT keyword), number of entries per row equals the number of
x-coordinates for that network
Row
Zelev
FLAG
Keyword to specify that flagpole receptor heights follow
(optional)
Indicates which row (y-coordinate fixed) is being input (Row=l
means first, i.e., southmost row)
An array of receptor heights (m) above local terrain elevation for
a particular Row (flagpole receptors), number of entries per row
equals the number of x-coordinates for that network
Row
Z flag
END
Indicates the END of GRIDCART inputs for a particular network,
repeated for each new Netid
3-12
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The ELEV and FLAG keywords are optional inputs, and are only needed if elevated
terrain or flagpole receptor heights are to be provided. If the ELEV keyword is used and the
preprocessor is being run with the TERRHGTS option set to EXTRACT (see Section 3.2.2), then
the elevated terrain height inputs will be ignored by the preprocessor, and a non-fatal warning
message will be generated. If the TERRHGTS option is set to PROVIDED, and no elevated
terrain heights are entered, the elevations will default to 0.0 meters, and warning messages will
also be generated. If the FLAG keyword is used and the FLAGPOLE option has not been
specified on the CO pathway (see Section 3.2.3), then the flagpole data will be ignored when the
output receptor data are generated. If the FLAGPOLE option is selected, and the FLAG
keyword is not used, then the default flagpole height will be output with the receptor data.
The order of cards within the GRIDCART subpathway is not important, as long as all
inputs for a particular network are contiguous and start with the STA secondary keyword and
end with the END secondary keyword. It is not even required that all ELEV cards be
contiguous, although the input file will be more readable if a logical order is followed. The
network ID is also not required to appear on each runstream image (except for the STA card).
The program will assume the previous ID if none is entered, similar to the use of continuation
cards for pathway and keywords. Thus, the following two examples produce the same 8X4
Cartesian grid network:
3-13
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RE
GRIDCART
CAR1
STA
RE
GRIDCART
CAR1
XPNTS
-500.
-400
-200.
-100.
100
200
. 400.
500.
RE
GRIDCART
CAR1
YPNTS
-500.
-250
250.
500.
RE
GRIDCART
CAR1
ELEV
1
10.
10.
10. 10.
10.
10.
10.
10.
RE
GRIDCART
CAR1
ELEV
2
20.
20.
N)
O
N)
O
20.
20.
20.
20.
RE
GRIDCART
CAR1
ELEV
3
30.
30.
30. 30.
30.
30.
30.
30.
RE
GRIDCART
CAR1
ELEV
4
40.
40.
o
o
40.
40.
40.
40.
RE
GRIDCART
CAR1
FLAG
1
10.
10.
10. 10.
10.
10.
10.
10.
RE
GRIDCART
CAR1
FLAG
2
20.
20.
N)
O
N)
O
20.
20.
20.
20.
RE
GRIDCART
CAR1
FLAG
3
30.
30.
30. 30.
30.
30.
30.
30.
RE
GRIDCART
CAR1
FLAG
4
40.
40.
o
o
40.
40.
40.
40.
RE
GRIDCART
CAR1
END
RE
GRIDCART
CAR1
STA
XPNTS
-500.
-400
-200.
-100.
100
200
. 400.
500.
YPNTS
-500.
-250
250.
500.
ELEV
1
8*10
FLAG
1
8*10
ELEV
2
8*20
FLAG
2
8*20
ELEV
3
8*30
FLAG
3
8*30
ELEV
4
8*40
FLAG
4
8*40
RE
GRIDCART
CAR1
END
The Row parameter on the ELEV and FLAG inputs may be entered as either the row
number, i.e., 1, 2, etc., or as the actual y-coordinate value, e.g., -500., -250., etc. in the example
above. The program sorts the inputs using Row as the index, so the result is the same. The
above example could therefore be entered as follows, with the same result:
RE GRIDCART CAR1 STA
XPNTS
-500.
-400
YPNTS
-500.
-250
ELEV
-500.
8*10.
FLAG
-500.
8*10.
ELEV
-250.
8*20.
FLAG
-250.
8*20.
ELEV
250.
8*30.
FLAG
250.
8*30.
ELEV
500.
8*40.
FLAG
500.
8*40.
-200. -100. 100. 200. 400. 500.
250. 500.
RE GRIDCART CAR1 END
3-14
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Of course, one must use either the row number or y-coordinate value consistently within each
network to have the desired result.
The following simple example illustrates the use of the XYINC secondary keyword to
generate a uniformly spaced Cartesian grid network. The resulting grid is 11 x 11, with a
uniform spacing of 1 kilometer (1000. meters), and is centered on the origin (0., 0.). No elevated
terrain heights or flagpole receptor heights are included in this example.
RE
GRIDCART
CGI
STA
XYINC
-5000.
11 1000.
-5000.
11 1000.
RE
GRIDCART
CGI
END
3.4.1.2 Polar Grid Receptor Networks.
Polar receptor networks are defined by use of the GRIDPOLR keyword. The
GRIDPOLR keyword may also be thought of as a "subpathway," in that there is a series of
secondary keywords that are used to define the start and the end of the inputs for a particular
network, and to select the options for defining the receptor locations that make up the network.
The syntax and type of the GRIDPOLR keyword are summarized below:
Syntax:
RE GRIDPOLR Netid
STA
ORIG
Xinit Yinit,
or
ORIG
Srcid
DIST
Ringl Ring2
Ring3 ... Ringn
DDIR
Dirl Dir2
Dir3 ... Dirn,
or
GDIR
Dirnum Dirini
Dirinc
ELEV
Dir Zelevl Zelev2 Zelev3 ...
Zelevn
FLAG
Dir Zflagl Zflag2 Zflag3 ...
Z flagn
END
Type:
Optional, Repeatable
3-15
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where the parameters are defined as follows:
Netid
Receptor network identification code (up to eight alphanumeric
characters)
STA
Indicates STArt of GRIDPOLR inputs for a particular network, repeat
for each new Netid
ORIG
Xinit
Yinit
Srcid
Keyword to specify the origin of the polar network (optional)
x-coordinate for origin of polar network
y-coordinate for origin of polar network
Source ID of source used as origin of polar network
DIST
Ringl
Ringn
Keyword to specify distances for the polar network
Distance to the first ring of polar coordinates
Distance to the 'nth' ring of polar coordinates
DDIR
Dirl
Dirn
Keyword to specify discrete direction radials for the polar network
First direction radial in degrees (1 to 360)
The 'nth' direction radial in degrees (1 to 360)
GDIR
Dirnum
Dirini
Dirinc
Keyword to specify generated direction radials for the polar
network
Number of directions used to define the polar system
Starting direction of the polar system
Increment (in degrees) for defining directions
ELEV
Dir
Zelev
Keyword to specify that receptor elevations follow (optional)
Indicates which direction is being input
An array of receptor terrain elevations for a particular direction
radial (default units of meters may be changed to feet by use of RE
ELEVUNIT keyword), number of entries per radial equals the number
of distances for that network
FLAG
Dir
Z flag
Keyword to specify that flagpole receptor heights follow (optional)
Indicates which direction is being input
An array of receptor heights above local terrain elevation for a
particular direction (flagpole receptors)
END
Indicates END of GRIDPOLR subpathwav, repeat for each new Netid
The ORIG secondary keyword is optional for the GRIDPOLR inputs. If omitted, the
program assumes a default origin of (0..0..) in x.v coordinates. The ELEV and FLAG keywords
3-16
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are also optional inputs, and are only needed if elevated terrain or flagpole receptor heights are to
be provided. If elevated terrain is being provided, then the ELEV inputs are needed for each
receptor. If the ELEV keyword are used and the program is being run with the TERRHGTS
option set to EXTRACT (see Section 3.2.2), then the elevated terrain height inputs will be
ignored by the preprocessor, and a non-fatal warning message will be generated. If the
TERRHGTS option is set to PROVIDED and no elevated terrain heights are entered, the
elevations will default to 0.0 meters, and warning messages will also be generated. If the FLAG
keyword is used and the FLAGPOLE option has not been specified on the CO pathway (see
Section 3.2.3), then the flagpole data will be ignored when the output receptor data are
generated. If the FLAGPOLE option is selected, and the FLAG keyword is not used, then the
default flagpole height will be output with the receptor data.
As with the GRIDCART keyword described above, the order of cards within the
GRIDPOLR subpathway is not important, as long as all inputs for a particular network are
contiguous and start with the STA secondary keyword and end with the END secondary
keyword. It is not even required that all ELEV cards be contiguous, although the input file will
be more readable if a logical order is followed. The network ID is also not required to appear on
each runstream image (except for the STA card). The program will assume the previous ID if
none is entered, similar to the use of continuation cards for pathway and keywords.
The following example of the GRIDPOLR keyword generates a receptor network
consisting of 180 receptor points on five concentric distance rings centered on an assumed
default origin of (0.,0.). The receptor locations are placed along 36 direction radials, beginning
with 10. degrees and incrementing by 10. degrees in a clockwise fashion.
RE
GRIDPOLR
POL1
STA
DIST
100.
300.
500.
1000.
2000.
GDIR
36
10.
10.
RE
GRIDPOLR
POL1
END
3-17
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Another example is provided illustrating the use of a non-zero origin, discrete direction radials
and the specification of elevated terrain and flagpole receptor heights:
RE
GRIDPOLR
POL1
STA
ORIG
500.
500
DIST
100.
300
500.
1000. 2000.
DDIR
90.
180
270.
360.
ELEV
90.
5.
10
15.
20.
25.
ELEV
180.
5.
10
15.
20.
25.
ELEV
270.
5.
10
15.
20.
25.
ELEV
360.
5.
10
15.
20.
25.
FLAG
90.
5.
10
15.
20.
25.
FLAG
180.
5.
10
15.
20.
25.
FLAG
270.
5.
10
15.
20.
25.
FLAG
360.
5.
10
15.
20.
25.
RE
GRIDPOLR
POL1
END
As with the GRIDCART keyword described earlier, the user has the option of specifying the
radial number (e.g. 1, 2, 3, etc.) on the ELEV and FLAG inputs, or the actual direction
associated with each radial.
3.4.2 Using Multiple Receptor Networks
For some modeling applications, the user may need a fairly coarsely spaced network
covering a large area to identify the area of significant impacts for a plant, and a denser network
covering a smaller area to identify the maximum impacts. To accommodate this modeling need,
the AERMAP preprocessor allows the user to specify multiple receptor networks in a single run.
The user can define either Cartesian grid networks or polar networks, or both. With the use of
the PRIG option in the GRIDPOLR keyword, the user can easily place a receptor network
centered on the facility being permitted, and also place a network centered on another
background source known to be a significant contributor to high concentrations. Alternatively,
the polar network may be centered on a receptor location of special concern, such as a nearby
Class I area.
3-18
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As noted in the introduction to this section, the program initially allows up to 10 receptor
networks in a single run. This limit can be changed by modifying the Fortran PARAMETER
statement in the AERMAP.INC file and recompiling the program. There are also limits on the
number of distances or directions (or the number of x-points and the number of y-points for
Cartesian grids) that can be specified for each network. These are initially set to 100 distances
or x-points and 100 directions or y-points. These limits are also controlled by Fortran
PARAMETER statements in AERMAP.INC, and may be modified.
3.4.3 Specifying Discrete Receptor Locations
In addition to the receptor networks defined by the GRIDCART and GRIDPOLR
keywords described above, the user may also specify discrete receptor points for modeling
impacts at specific locations of interest. This may be used to model critical receptors, such as
the locations of schools or houses, nearby Class I areas, or locations identified as having high
concentrations by previous modeling analyses. The discrete receptors may be input as either
Cartesian x,y points (DISCCART keyword) or as polar distance and direction coordinates
(DISCPOLR keyword). Both types of receptors may be identified in a single run. In addition,
for discrete polar receptor points the user specifies the source location used as the origin for the
receptor on the SO LOCATION card (see Section 3.3).
3.4.3.1 Discrete Cartesian Receptors.
Discrete Cartesian receptors are defined by use of the DISCCART keyword. The syntax
and type of this keyword are summarized below:
Syntax:
RE DISCCART Xcoord Ycoord (Zelev) (Zflag)
Type:
Optional, Repeatable
3-19
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where the Xcoord and Ycoord parameters are the x-coordinate and y-coordinate (m),
respectively, for the receptor location. The Zelev parameter is an optional terrain elevation (m).
The Zflag parameter is the optional receptor height above ground (m) for modeling flagpole
receptors. All of the parameters are in units of meters, except for Zelev, which defaults to meters
but may be specified in feet by use of the RE ELEVUNIT keyword. Note that the output
elevations will always be in meters, regardless of input units.
If neither the elevated terrain option (Section 3.2.7) nor the flagpole receptor height
option (Section 3.2.8) are used, then the optional parameters are ignored if present. If only the
elevated terrain height option is used (no flagpoles), then the third parameter (the field after the
Ycoord) is read as the Zelev parameter. If only the flagpole receptor height option is used (no
elevated terrain), then the third parameter is read as the Zflag parameter. If both options are
used, then the parameters are read in the order indicated for the syntax above. If the optional
parameters are left blank, then default values will be used. The default value for Zelev is 0.0,
and the default value for Zflag is defined by the CO FLAGPOLE card (see Section 3.2.8). Note:
If both the elevated terrain and flagpole receptor height options are used, then the third parameter
will always be used as Zelev, and it is not possible to use a default value for Zelev while entering
a specific value for the Zflag parameter.
3.4.3.2 Discrete Polar Receptors.
Discrete polar receptors are defined by use of the DISCPOLR keyword. The syntax and
type of this keyword are summarized below:
Syntax:
RE DISCPOLR Srcid Dist Direct (Zelev) (Zflag)
Type:
Optional, Repeatable
where the Srcid is the alphanumeric source identification for one of the sources defined on the
SO pathway which will be used to define the origin for the polar receptor location. The Dist and
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Direct parameters are the distance in meters and direction in degrees for the discrete receptor
location. Degrees are measured clockwise from north. The Zelev parameter is an optional
terrain elevation for the receptor. The unit of Zelev is in meters, unless specified as feet by the
RE ELEVUNIT keyword. The Zflag parameter is the optional receptor height above ground
(meters) for modeling flagpole receptors.
If neither the elevated terrain option (Section 3.2.7) nor the flagpole receptor height
option (Section 3.2.8) is used, then the optional parameters are ignored if present. If only the
elevated terrain height option is used (no flagpoles), then the third parameter (the field after the
Ycoord) is read as the Zelev parameter. If only the flagpole receptor height option is used (no
elevated terrain), then the third parameter is read as the Zflag parameter. If both options are
used, then the parameters are read in the order indicated for the syntax above. If the optional
parameters are left blank, then default values will be used. The default value for Zelev is 0.0,
and the default value for Zflag is defined by the CO FLAGPOLE card (see Section 3.2.8). Note:
If both the elevated terrain and flagpole receptor height options are used, then the fourth
parameter will always be used as Zelev, and it is not possible to use a default value for Zelev
while entering a specific value for the Zflag parameter.
3.4.3.3 Discrete Cartesian Receptors for EVALFILE Output.
The EVALCART keyword is used to define discrete Cartesian receptor locations, similar
to the DISCCART keyword, but it also allows for grouping of receptors, e.g., along arcs. It is
designed to be used with the EVALFILE option of AERMOD. The syntax and type for the
EVALCART keyword are summarized below:
Syntax: RE EVALCART Xcoord Ycoord Zelev Zflag Arcid (Name)
Type: Optional, Repeatable
3-21
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where the Xcoord and Ycoord parameters are the x-coordinate and y-coordinate (m),
respectively, for the receptor location. The Zelev parameter is the terrain elevation (m) for the
receptor. The Zflag parameter is the receptor height above ground (m) for modeling flagpole
receptors. All of the parameters are in units of meters, except for Zelev, which default to meters
but may be specified in feet by use of the RE ELEVUNIT keyword. Note that the output
elevations will always be in meters, regardless of the input units. The Arcid parameter is the
receptor grouping identification, which may be up to eight characters long, and may be used to
group receptors by arc. The Name parameter is an optional name field that may be included to
further identify a particular receptor location. The Name parameter is ignored by the
preprocessor program and the AERMOD model.
3.5 OUTPUT PATHWAY INPUTS AND OPTIONS
The OUtput pathway is used to define filenames for the receptor and optional source
location output data. There are only two keywords available on the output pathway, besides
STARTING and FINISHED, one for receptor output data and the other for source location
output data. The syntax and type of the RECEPTOR keyword are summarized below:
Syntax: ou receptor Recfil
Type: Mandatory, Non-repeatable
where Recfil specifies the filename (up to 60 characters) for the receptor output data.
The syntax and type of the SOURCLOC keyword are summarized below:
Syntax: ou sourcloc srcfile
Type: Optional, Non-repeatable
3-22
-------
where Srcfil specifies the filename (up to 60 characters) for the source location output data. The
SOURCLOC keyword must be specified if the runstream contains a source pathway and the user
specifies that terrain heights are to be extracted from the DEM data.
3-23
-------
4.0 TECHNICAL DESCRIPTION
This section describes the technical details of the AERMAP preprocessor. This is meant
to give the user a better understanding of the working of this preprocessor.
4.1 DETERMINING RECEPTOR HILL HEIGHT SCALES
For applications involving elevated terrain, the AERMOD model requires a hill height
scale which is used to calculate the critical dividing streamline height, Hcrit, for each receptor.
The primary purpose of the AERMAP terrain preprocessor is to determine the hill height scale
(hc) for each receptor, based on the following procedure:
1. Read the header record of each DEM file named in the runstream (input) and retain the
"highest elevation" value found in each record.
2. Determine and store the elevation height for each receptor (and source).
3. For each receptor, use the receptor elevation height as the initial controlling hill height
scale.
4. Search for the controlling hill height in the DEM file in which the receptor is located.
This is done by calculating the slope between the receptor and each node based on
respective distance and elevation difference ( See Figure 2-3). If the slope is 10% or
greater, the DEM node elevation is compared to the controlling hill height scale. If
higher, the controlling hill height scale is replaced by the node elevation value as the new
controlling hill height scale. All the nodes within the DEM file that are within the
DOMAIN are searched.
4-1
-------
5. Using the respective highest elevation value of each remaining DEM file,
calculate the slope between the receptor and the nearest point on each of the
remaining DEM files. Use the respective highest elevation and the receptor
elevation to calculate an initial slope. If the initial slope is greater than 10% for a
particular DEM file, use the steps in procedure 4 to search for a controlling hill
height in this DEM file. If a higher value is found, update the controlling hill
height.
6. Repeat Procedure 5 until all applicable DEM files have been searched for a controlling
hill height scale for each receptor.
4.2 DIGITAL ELEVATION MODEL (DEM) DATA
The USGS distributes DEM data in several scales from the 1-degree series at a scale of
1:250,000 down to the 7.5-minute series at a scale of 1:24,000. AERMAP can process any of
these scales. However, AERMAP has not been programmed to process more than one scale at a
time nor has it been yet tested using more than one basic quadrangle size (eg 7.5 x 18 minutes,
7.5 x 15 minutes, 7.5 x 11.5 minutes, and 7.5 x 10 minutes) as found in the State of Alaska.
Outside of Alaska, the normal block size for a 7.5-minute series file is 7.5 x 7.5 minutes. It is
preferred that the user use the 7.5-minute data whenever possible. The 1-degree DEM series
provides coverage in 1 X 1-degree blocks; two such files provide the same coverage as a
standard 1:250,000-scale map series quadrangle. The 1-degree data also has different block size
for the State of Alaska and like the 7.5-minute series, the block sizes are dependent upon the
latitude. The 1-degree block sizes are discussed below.
A 7.5-minute DEM has the following characteristics:
The data consist of a regular array of elevations referenced horizontally in the
UTM coordinate system.
4-2
-------
The unit of coverage is a 7.5-minute quadrangle.
The data are ordered from south to north in profiles that are ordered from west to
east.
The data are stored as profiles in which the horizontal spacing of the elevations
along and between each profile is either 10 or 30 m.
The profiles do not always have the same number of elevations (nodes) because
of the variable angle between the quadrangle's true north and the grid north of the
UTM coordinate system.
Elevations for the continental U.S. are either meters, feet, decimeters, or decifeet
referenced to mean sea level. DEM's of low-relief terrain or generated from
contour maps with intervals of 10 ft (3 m) or less are generally recorded in feet.
DEM's of moderate to high-relief terrain or generated from maps with terrain
contour intervals greater than 10 ft are generally recorded in meters. A rare few
are in decifeet or decimeters.
Profiles for 7.5-minute DEM.'S are generated by using a UTM Cartesian coordinate
system as a base. The profiles are clipped to the straight-line intercept among the four
geographic corners of the quadrangle an approximation of the geographic map boundary as
shown in Figure 4-1.
4-3
-------
B» 1
3C m
' -.*» 30>-v r-3' ~
' GcV pc-^:^
>« a j^on*,-# i
arwa ~-e»=.i- s <_*v»
FIGURE 4-1 STRUCTURE OF A 7.5-MINUTE DEM DATA FILE
The UTM coordinates of the four corners (i.e., Pt 1, Pt 2, Pt 3 and Pt 4 in Figure 4-1) of the 7.5-
minute DEM's are listed in the type A (header) record, data element 11. The UTM coordinates
of the starting points of each profile are listed in the type B record (profiles), shown in Table 4-2,
data element 3. Because of the variable orientation of the quadrilateral in relation to the UTM
coordinate system, profiles intersect the east and west boundaries of the quadrangle, as well as
the north and south boundaries, as shown in Figure 4-1. In addition, 7.5-minute DEM's have
profile easting values that are continuous from one DEM to the adjoining DEM only if the
adjoining DEM is contained within the same UTM zone. This is illustrated in Figure 4-1 with
the use of non-filled in circles outside the border of the quadrangle. The non-filled in circles
represent nodes located in adjacent DEM files.Note: the spacing in the x and y directions can
also be 10 meters as well as the stated 30 meters. Finer resolutions may exist in the future and
AERMAP should be able to process them.
4-4
-------
The 1-degree DEM data has the following characteristics (U.S. Dept. of Interior, 1993):
The data consist of a rectangular array of elevations referenced horizontally on
the geographic (latitude/longitude) coordinate system (Figure 4-2).
The unit of coverage is a 1-degree by 1-degree block. Elevation data on the
integer degree lines (all four sides of the DEM file) correspond with the same
node elevations of the surrounding eight DEM blocks. Four blocks are located on
the DEM sides and four DEMs have a common point in the corners.
Elevations are in meters relative to mean sea level.
The data are ordered from south to north in profiles that are ordered from west to
east.
Spacing of the elevations along each profile is 3 arc-seconds. The first and the
last data points are the integer degrees of latitude. A profile, therefore, contains
1201 elevations.
Spacing between profiles varies by latitude; however, the first and last data points
are at the integer degrees of longitude. For the contiguous United States, the
spacing is 3 arc-seconds. Between 50 degrees N and 70 degrees N, the spacing is
6 arc-seconds. For the remainder of Alaska, north of 70 degrees N the spacing is
9 arc-seconds.
4-5
-------
P'. 3
A* ¦ 3 arc itcordS
A* - 3 arc stccxids
¦ Eieviiion coin*
* P -*i com bio**} profile
Q * Comnr of D£M polygon
(r bi«*f
Pt 1
PI *
p*
Ax
FIGURE 4-2 STRUCTURE OF A 1 -DEGREE DEM DATA FILE FOR THE LOWER
LATITUDES
There are two types of records in the DEM files. The first is a header record consisting
of general information about the DEM data file. This record appears only once in the file and is
always the first record. The second record type contains the elevation data along each profile.
This second record is repeated for each profile. The structure of these two record types are
described in Tables 4-1 and 4-2, respectively. A complete description of the record structure is
in a publication issued by the USGS (U.S. Dept. of Interior, 1993) and available on the Internet.
4-6
-------
Table 4-1. DEM Data Elements - Logical Record Type A (File Header)
Type Physical Record Format
Data (FORTRAN ASCII Starting Ending Comment
Element Notation) Format byte byte
1 File name
ALPHA
A40
40
DEM quadrangle name.
Free Format Text
Filler
ALPHA
A40
41
81
Free format descriptor field, contains useful information related to
digital process such as digitizing instrument, photo codes, slot
widths, etc.
135
Process Code
ALPHA
A1
136
Code 1=GPM
2=Manual Profile
3=DLG2DEM (includes any DLG type process such as
CTOG or LINETRACE)
4=DCASS
2 MC origin code
ALPHA
A4
141
144
Mapping Center origin Code. Valid codes are EMC, WMC,
MCMC, RMMC, FS, GPM2.
DEM level code
INTEGER* 2
16
145
150
Code 1=DEM-1
2=DEM-2
3=DEM-3
4 Code defining
elevation pattern
(regular or random)
INTEGER* 2
16
151
156
Code l=regular
2=random is reserved for
future use.
4-7
-------
Table 4-1. DEM Data Elements - Logical Record Type A (continued)
Type Physical Record Format
Data (FORTRAN ASCII Starting Ending Comment
Element Notation) Format byte byte
Code defining INTEGER* 2 16 157 162 Code 0=Geographic
ground planimetric 1=UTM
reference system 2=State plane
Code 0 represents the geographic (latitude/longitude) system for
1-degree DEM's. Code 1 represents the current use of the UTM
coordinate system for 7.5-minute DEM's.
Code defining
zone in ground
planimetric
reference system
INTEGER* 2
16
163
168
Codes for State plane and UTM coordinate
zones for 7.5-minute DEM's. Code
is set to zero for 1-degree DEM's.
Map projection
parameters
REAL* 8
15D24.15
169
528
Definition of parameters for various projections.
All 15 fields of this element are set to zero and should be
ignored.
Code defining unit
of measure for
ground planimetric
coordinates through-
out the file
INTEGER* 2
16
529
534
Code 0=radians
l=feet
2=meters
3=arc-seconds
Normally set to code 2 for 7.5-minute DEM's. Always set to code
3 for 1-degree DEM's.
4-8
-------
Table 4-1. DEM Data Elements - Logical Record Type A (continued)
Type Physical Record Format
Data (FORTRAN ASCII Starting Ending Comment
Element Notation) Format byte byte
Code defining unit of measure
for elevation coordinates
throughout the file
INTEGER* 2
16
535
540
Code l=feet
2=meters
Normally code 2, meters, for
7.5-minute and 1-degree DEM's.
10 Number (n) of sides in the polygon
which defines the coverage
of the DEM file
INTEGER* 2
16
541
546
n=4.
11
A 4,2 array con-
taining the ground
coordinates of the
four corners for
the DEM
REAL* 8
4(2D24.15)
547
738
The coordinates of the quadrangle
corners are ordered in a clockwise
direction beginning with the
southwest corner, in units specified
in data element 8.
12 A two-element array containing
minimum and maximum
elevations for the DEM
REAL* 8
2D24.15
739
786
The values are in the unit of
measure given by data element 9 in
this record.
13 Counterclockwise angle (in radians)
from the primary axis of ground
planimetric reference to the primary
axis of the DEM local reference system
REAL* 8
D24.15
787
810
Set to zero to align
with the coordinate system specified
in element 5.
Table 4-1. DEM Data Elements - Logical Record Type A (continued)
4-9
-------
Data
Element
Type
(FORTRAN
Notation)
Physical Record Format
ASCII Starting Ending
Format byte byte
Comment
14 Accuracy code for INTEGER*2 16 811 816
elevations
15 A three-element array REAL*4 3E12.6 817 852
of DEM spatial resolu-
tion for x, y, z. Units of
measure are consistent
with those indicated by data
elements 8 and 9 in this
record
16 A two-element array containing INTEGER*2 216 853 864
the number of rows and columns (m,n)
of profiles in the DEM
Note: Old format stops here
Code 0=unknown accuracy
l=accuracy information is given
in logical record type C (not used).
These elements are usually set to; 30, 30, 1 for
7.5-minute DEM's, and 2,2,1 for 30-minute DEM's;
3, 3, 1 for 1-degree DEM's.
2, 1, 1 for high resolution DEM's in Alaska
3, 2, 1 for low resolution DEM's in Alaska
7.5 minute DEM's will eventually be converted
To geographies, i.e., 1, 1 ,1.
When the row value m is set to 1 the
n value describes the number of
columns in the DEM file. Raw GPM data files
are set to m=16, n=16.
4-10
-------
Table 4-1. DEM Data Elements - Logical Record Type A (continued)
Data
Element
Type
(FORTRAN
Notation)
Physical Record Format
ASCII Starting Ending
Format byte byte
Comment
17
Largest primary
contour interval
INTEGER*2
15
865 869
Present only if two or more
primary intervals exist.
18
Source contour
interval units
INTEGER*!
II
870
Corresponds to the units of the map
largest primary contour interval
0=N.A., l=feet, 2=meters.
19
Smallest primary
INTEGER*2
15
871 875
Smallest or only primary contour interval
20
Source contour
interval units
INTEGER*!
II
876
Corresponds to the units of the map
smallest primary contour interval.
l=feet, 2=meters.
4-11
-------
Table 4-1. DEM Data Elements - Logical Record Type A (continued)
Type Physical Record Format
Data (FORTRAN ASCII Starting Ending Comment
Element Notation) Format byte byte
21 Data source date INTEGER*2 14 877 880 YYMM two-digit year and two-digit month
MM = 00 for source having year only.
22 Data inspection/ INTEGER*2 14 881 884 YYMM two-digit year and two-digit month,
revision date
23 Inspection/ ALPHA* 1 A1 885 "I" or "R"
revision flag
24 Data validation INTEGER* 1 II 886 0= No validation performed,
flag
1=TESDEM (record C added) no quali-
tative test (no DEM Edit System [DES] review).
2=Water body edit and TESDEM run.
3=DES (includes water edit) no qualitative test (no TESDEM).
4=DES with record C added, qualitative and quantitative tests for
level 1 DEM.
5=DES and TESDEM qualitative and quantitative tests for
levels 2 and 3 DEM's.
4-12
-------
Table 4-1. DEM Data Elements - Logical Record Type A (continued)
Data
Element
Type
(FORTRAN
Notation)
Physical Record Format
ASCII Starting Ending
Format byte byte
Comment
25
Suspect and void
area flag
INTEGER*!
12
887
0=none
l=suspect areas
2=void areas
3=suspect and void areas
26
Vertical datum
INTEGER*!
12
890
l=local mean sea level
2=National Geodetic Vertical
Datum 1929 (NGVD 29)
3=North American Vertical
Datum 1988 (NAVD 88)
4-13
-------
Table 4-1. DEM Data Elements - Logical Record Type A (continued)
Type Physical Record Format
Data (FORTRAN ASCII Starting Ending Comment
Element Notation) Format byte byte
27 Horizontal datum
INTEGER* 1
12
891
892
l=North American Datum 1927 (NAD 27)
2=World Geodetic System 1972 (WGS 72)
3=WGS 84
4=NAD 83
5=01d Hawaii Datum
6=Puerto Rico Datum
7=NAD 83 Provisional (shifts in
horizontal coordinates are
computed, but old DEM nodes
are not resampled)
28 Data Edition
INTEGER*2
14
893
896
01-99 Primarily a DMA specific field.
29 Percent Void
INTEGER* 2
14
897
900
If element 25 indicates a void, this field (right justified) contains
the percentage of nodes in the file set to void (-32,767).
4-14
-------
Table 4-2. DEM Data Elements - Logical Record Type B (Data Record)
Type Physical Record Format
Data (FORTRAN ASCII Starting Ending Comment
Element Notation) Format byte byte
A two-element array
containing the row
and column identifi-
cation number of the
DEM profile con-
tained in this
record
INTEGER* 2
216
12
The row/column numbers
may range from 1 to m and
1 to n. The row number is normally
set to 1. The column identification
is the profile sequence number.
A two-element array
containing the number
INTEGER* 2
216
13
24
The first element in the field corresponds
to the number of rows and columns
(m, n) of elevations
in the DEM profile
of nodes in this profile. The second
element is set to 1, specifying 1 column per B record.
A two-element array
containing the ground
planimetric coordinates (X,Y)
of the first elevation in the profile
REAL* 8
2D24.15
25
72
See Figures 4-1 and 4-2.
Elevation of local
datum for the
profile
REAL* 8 D24.15 73 96 The values are in the units of
measure given by data element 9,
logical record type A.
Table 4-2. DEM Data Elements - Logical Record Type B (continued)
4-15
-------
Data
Element
Type
(FORTRAN
Notation)
Physical Record Format
ASCII Starting Ending
Format byte byte
Comment
5 A two-element array REAL* 8 2D24.15 97 144
of minimum and
maximum elevations
for the profile
A m,n array of
elevations for the
profile. Elevations
are expressed in
units of resolution
INTEGER* 2
mn(I6) 6x(146 or 170)
146 = max for
first block. 170 = max
for subsequent blocks
The values are in the unit of
measure given by data element 9 in
logical record type A.
A value in this array would be
multiplied by the spatial resolution
value and added to the elevation of the
local elevation datum for the element profile (data element 4 in
this record) to obtain the elevation for the point.
4-16
-------
4.3 DATA MANIPULATION BY AERMAP
The AERMAP preprocessor creates a direct access binary file and an index file for each DEM
file containing only that portion of the DEM file that falls within the user-specified domain. These
files are temporary, and enable the program to determine the elevation at a DEM node very efficiently.
For example, if four adjacent DEM files are specified and a domain is defined as shown in Figure 2-1,
then AERMAP will produce four direct access binary files, one for each DEM file, containing a subset
of the terrain elevation data that lies within the domain (files 1, 2, 3 and 4 in Figure 2-1). The
elevations in the direct access files are stored in meters. The order of the elevation points in these files
will be the same as that of the original DEM file except that the coordinates of the baseline of the
profile and the number of nodes in the profiles might be different. The new values for the baseline
location and number of nodes are written to the index file corresponding to each DEM file. The
program creates the direct access files using the same name as the DEM file but with an extension of
'DIR'. Similarly the index file corresponding to a DEM file will be the same file name but with an
extension of'IDX'. These files are deleted when the program ends.
If 7.5 minute DEM data are used and Nada is not set to zero, AERMAP will convert NAD 27
data to NAD 83. This will assure that all the receptors, sources, and elevations are using the same
geodetic reference (i.e. NAD83). Otherwise, some of the elevations extracted could be more than 100
meters in error in the horizontal as depicted in Figure 4-3. This is because of the difference in
geodetic reference. The NAD 27 datum is based on a mathematical representation of the earth while
the NAD 83 data is based on satellite and earth-centric data. This creates physical location differences
when coordinate system are laid on top of the theoretic representation of the earth to where the DEM
datasets will have noticeable overlaps and/or no coverage areas between adjacent DEM maps (See
Figure 2-3). In other words, even though each adjacent map may have the same corner coordinates
with the same latitude and longitude, the underlying point with respect to the earth may be different by
more than 100 meters. It may also reside between maps where there are no closeby elevation
nodes.
4-17
-------
4.4 DETERMINING RECEPTOR (SOURCE) ELEVATIONS
If the user requests the preprocessor to extract the receptor (and optional source) elevations
from the DEM data using the CO TERRHGTS EXTRACT card, or if the CO TERRHGTS
keyword is omitted, the following procedure is used to determine the elevation:
For each receptor, the program searches through the DEM data index files to
determine the two profiles (longitudes or eastings) that straddle this receptor.
For each of these two profiles, the program then searches through the nodes in the
index file to determine which two rows (latitudes or northings) straddle the
receptor.
The program then calculates the coordinates of these four points and determines the
DEM direct access file and the record numbers that correspond to these points.
It reads the elevations for these four points from the appropriate direct access file.
If there are less than four points, the program will search the other adjacent DEM
files following the above steps. The program will retain the closest node found in
the northwest, northeast, southeast, and southwest quadrants. The quadrants'
common point is the receptor location. Distances to, and the elevations of these
DEM nodes are retained.
A 2-dimensional distance-weighted interpolation is used to determine the elevation
at the receptor location based on the elevations at the four nodes. The weighting
equation is:
4-18
-------
Weighing Factor (w) = 1/distl + l/dist2 + l/dist3 + l/dist4.
Elevation = elevl/(distl*w) + elev2/(dist2*w) + elev3/(dist3*w) + elev4/(dist4*w)
where w is the weighting factor.
When 7.5-minute DEM data are used, a receptor or source location may fall outside the range of
the profiles but remain inside a DEM file boundaries (see Figure 4-1) or they may fall between
the DEM files when the DEM files are from different datums. Elevations for all receptors or
sources located near the edges of a DEM file are assigned values based on the nodes that are
closest to the receptor or source location and may include elevations from two or more DEM files.
4-19
-------
5.0 REFERENCES
Cimorelli, A.J., Perry, S.G., Venkatram, A., Weil, J.C., Paine, R.J., Wilson, R.B., Lee, R.F., Peters,
W.D., Brode, R.W., Paumier, J.O., 2004: AERMOD: Description of Model Formulation.
EPA-454/R-03-004, U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina 27711.
Environmental Protection Agency, 1995: Industrial Source Complex (ISC3) Dispersion Model
User's Guide - Volume II. EPA-454/B-95-003b, U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711.
Environmental Protection Agency, 1998: Revised Draft User's Guide for the AMS/EPA Regulatory
Model - AERMOD. U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina 27711.
Environmental Research and Technology, 1987: User's Guide to the Rough Terrain Diffusion Model
(RTDM), Rev. 3.20. ERT Document No. P-D535-585. Environmental Research and
Technology, Inc., Concord, MA. (NTIS No. PB 88-171467)
Perry, S.G., D.J. Burns, L.H. Adams, R.J. Paine, M.G. Dennis, M.T. Mills, D.J. Strimaitis, R.J.
Yamartino and E.M. Insley, 1989: User's Guide to the Complex Terrain Dispersion Model
Plus Algorithms for Unstable Situations (CTDMPLUS) Volume 1; Model Description and
User Instructions. EPA Publication No. EPA-600/8-89-041. U.S. Environmental Protection
Agency, Research Triangle Park, NC. (NTIS No. PB 89-181424)
U.S. Department of the Interior, 1993: Digital Elevation Models Data User's Guide 5 ("Blue Book"),
U.S. Geological Survey, Earth Science Information Center.
U.S. Geological Survey, 1987: Map Projections - A Working Manual, U.S. Geological Survey Professional Paper 1
U.S. National Geodetic Survey, NADCON - North American Datum Conversion Utility,
http://www.ngs.noaa.gov:8Q/TOOLS/Nadcon/Nadcon.html
5-1
-------
APPENDIX A. ALPHABETICAL KEYWORD REFERENCE
This appendix provides an alphabetical listing of all of the keywords used by the
AERMAP preprocessor. Each keyword is identified as to the pathway for which it applies, the
keyword type (either mandatory or optional, and either repeatable or non-repeatable), and with a
brief description of the function of the keyword. For a more complete description of the
keywords, including a list of associated parameters, refer to the Detailed Keyword Reference in
Section 3 or the Functional Keyword/Parameter Reference in Appendix B.
A-l
-------
Keyword
Path
Type
Keyword Description
ANCHORXY
CO
M-N
Relates the origin of the user-specified coordinate system for
receptors to the UTM coordinate system
DATAFILE
CO
M-R
Specifies the names of the raw terrain data being provided to
the preprocessor
DATATYPE
CO
M-N
Specifies the type of the raw terrain data being provided to
the preprocessor
DISCCART
RE
0 - R
Defines the discretely placed receptor locations referenced to
a Cartesian system
DISCPOLR
RE
0 - R
Defines the discretely placed receptor locations referenced to
a polar system
DOMAINLL
CO
M-N
Allows the user to specify the domain extent in the latitude /
longitude coordinate system
DOMAINXY
CO
M-N
Allows the user to specify the domain extent in the UTM
coordinate system
ELEVUNIT
SO
RE
2:2;
i i
oo
Defines the input units for the source elevations (SO
pathway) or receptor elevations (RE pathway)
EVALCART
RE
0 - R
Defines discrete Cartesian receptors for use with EVALFILE
output
FINISHED
ALL
M-N
Identifies the end of inputs for a particular pathway
FLAGPOLE
CO
O-N
Specifies whether to accept receptor heights above local
terrain (m) for use with flagpole receptors, and allows for a
default flagpole height to be specified
GRIDCART
RE
0 - R
Defines a Cartesian grid receptor network
GRIDPOLR
RE
0 - R
Defines a polar receptor network
LOCATION
SO
0 - R
Specifies the location of sources
RECEPTOR
OU
M-N
Specifies the output filename for the receptor data
RUNORNOT
CO
M-N
Identifies whether to run program or process setup
information only
SOURCLOC
OU
O-N
Specifies the output filename for the source location data
STARTING
ALL
M-N
Identifies the start of inputs for a particular pathway
TERRHGTS
CO
O-N
Controls whether the receptor elevations should be extracted
from the terrain data or that the user-provided receptor
elevations should be used
TITLEONE
CO
M-N
First line of title for output
TITLETWO
CO
O-N
Optional second line of output title
A-2
-------
APPENDIX B. FUNCTIONAL KEYWORD/PARAMETER REFERENCE
This appendix provides a functional reference for the keywords and parameters used by the
input runstream files for the AERMAP preprocessor. The keywords are organized by functional
pathway, and within each pathway the order of the keywords is based on the function of the keyword
within the preprocessor. The pathways used by the preprocessor are as follows, in the order in which
they appear in the runstream file and in the tables that follow:
CO - for specifying overall job COntrol options; and
SO - for specifying SOurce location information (optional);
RE - for specifying REceptor information; and
OU - for specifying OUtput file information.
The pathways and keywords are presented in the same order as in the Detailed Keyword Reference in
Section 3, and in the Quick Reference at the end of the manual.
Two types of tables are provided for each pathway. The first table lists all of the keywords for
that pathway, identifies each keyword as to its type (either mandatory or optional and either repeatable
or non-repeatable), and provides a brief description of the function of the keyword. The second type
of table presents the parameters for each keyword, in the order in which they should appear in the
runstream file where order is important, and describes each parameter in detail.
The following convention is used for identifying the different types of input parameters.
Parameters corresponding to secondary keywords which should be input "as is" are listed on the tables
with all capital letters (they are underlined in the table). Other parameter names are given with an
initial capital letter and are not input "as is." In all cases, the parameter names are intended to be
descriptive of the input variable being represented, and they often correspond to the Fortran variable
names used in the preprocessor code. Parentheses around a parameter indicate that the parameter is
optional for that keyword. The default that is taken when an optional parameter is left blank is
explained in the discussion for that parameter.
B-l
-------
TABLE B-l
DESCRIPTION OF CONTROL PATHWAY KEYWORDS
CO Keywords
Type
Keyword Description
STARTING
M - N
Identifies the start of CONTROL pathway inputs
TITLEONE
M - N
First line of title for output
TITLETWO
0 - N
Optional second line of title for output
TERRHGTS
0 - N
Controls whether the receptor elevations should be extracted
from the user-provided terrain data or that the user-provided
receptor terrain elevations should be used
FLAGPOLE
0 - N
Specifies whether to accept receptor heights above local
terrain (m) for use with flagpole receptors, and allows for
default flagpole height to be specified
DATATYPE
M - N
Specifies the type of the raw terrain data being provided to
the preprocessor
DATAFILE
M - R
Specifies the names of the raw terrain data being provided to
the preprocessor
DOMAINLL
M1 - N
Allows the user to specify the domain extent in the latitude
/ longitude coordinate system
DOMAINXY
M1 - N
Allows the user to specify the domain extent in the UTM
coordinate system
ANCHORXY
M - N
Relates the origin of the user-specified coordinate system
for receptors to the UTM coordinate system
RUNORNOT
M - N
Identifies whether to run program or process setup
information only
FINISHED
M - N
Identifies the end of CONTROL pathway inputs
Type: M-Mandatory N - Non-Repeatable
O - Optional R - Repeatable
1) Either the DOMAINLL or the DOMAINXY keyword must be used.
B-2
-------
TABLE B-2
DESCRIPTION OF CONTROL PATHWAY KEYWORDS AND PARAMETERS
Keyword
Parameters
TITLEONE
Titlel
where:
Titlel
First line of title for output,
character string of up to 68 characters
TITLETWO
Title2
where:
Title2
Second line of title for output,
character string of up to 68 characters
TERRHGTS
EXTRACT or PROVIDED
where:
EXTRACT
PROVIDED
Instructs the preprocessor to determine the terrain heights
from the DEM data files provided by the user (default)
Forces the preprocessor to use the user-specified receptor
elevations that are entered on the receptor pathway (also
applies to source elevations specified on the optional
source pathway)
FLAGPOLE
(Flagdf)
where:
Flagdf
Default value for height of (flagpole) receptors above
local ground level, a default value of 0.0 m is used if
this optional parameter is omitted
DATATYPE
DEMI or DEM7
where:
DEMI
DEM7
Specifies that 1-degree DEM Data will be used
Specifies that 7.5-minute DEM data will be used
DATAFILE
Demfil
where:
Demfil
Identifies the name of the DEM data file
DOMAINLL
Lonmin Latmin Lonmax Latmax
where:
Lonmin
Latmin
Lonmax
Latmax
Longitude in decimal degrees for the lower right (SE)
corner of the domain
Latitude in decimal degrees for the lower right (SE) corner
of the domain
Longitude in decimal degrees for the upper left (NW) corner
of the domain
Latitude in decimal degrees for the upper left (NW) corner
of the domain
DOMAINXY
Xdmin Ydmin Zonmin Xdmax Ydmax Zonmax
where:
Xdmin
Ydmin
Zonmin
Xdmax
Ydmax
Zonmax
UTM East coordinate for the lower left (SW) corner of the
domain in meters
UTM North coordinate for the lower left (SW) corner of the
domain in meters
UTM Zone for the lower left (SW) corner of the domain
UTM East coordinate for the upper right (NE) corner of the
domain in meters
UTM North coordinate for the upper right (NE) corner of the
domain in meters
UTM Zone for the upper right (NE) corner of the domain
B-3
-------
TABLE B-2
DESCRIPTION OF CONTROL PATHWAY KEYWORDS AND PARAMETERS (Cont'd)
ANCHORXY
Xauser Yauser Xautm Yautm Zautm
where:
Xauser
The X coordinate of any geographic location (typically the
origin 0,0) in the user coordinate system in meters
Yauser
The Y coordinate of any geographic location (typically the
origin 0,0) in the user coordinate system in meters
Xautm
The UTM East coordinate of the same geographic location
specified as Xauser,Yauser in meters
Yautm
The UTM North coordinate of the same geographic location
specified as Xauser,Yauser in meters
Zautm
The UTM Zone of the same geographic location corresponding
to Xautm, Yautm
Nada
The datum from which the Xautm, Yautm coordinates were
drawn
RUNORNOT
RUN or
NOT
where:
RUN
Indicates to run full preprocessor calculations
NOT
Indicates to process setup data and report errors,
but to not run full preprocessor calculations
B-4
-------
TABLE B-3
DESCRIPTION OF SOURCE PATHWAY KEYWORDS
so
Keywords
Type
Keyword Description
STARTING
M - N
Identifies the start of SOURCE pathway inputs
LOCATION
M - R
Identifies source locations for use in extracting source
elevations
and/or to define the origin of discrete polar receptors
FINISHED
M - N
Identifies the end of SOURCE pathway inputs
B-5
-------
TABLE B-4
DESCRIPTION OF SOURCE PATHWAY KEYWORDS AND PARAMETERS
Keyword
Parameters
LOCATION
Srcid Srctyp Xs Ys (Zs)
where:
Srcid
Srctyp
Xs
Ys
Zs
Alphanumeric source ID, up to eight characters
Source tvpe: POINT, VOLUME, AREA, AREAPOLY, AREACIRC
x-coordinate (Eastincr) of source location, corner for AREA,
vertex for AREAPOLY, center for AREACIRC (m)
y-coordinate (Northing) of source location (m)
Optional z-coordinate of source location (elevation above
mean sea level in meters)
B-6
-------
TABLE B-5
DESCRIPTION OF RECEPTOR PATHWAY KEYWORDS
RE Keywords
Type
Keyword Description
STARTING
M - N
Identifies the start of RECEPTOR pathway inputs
ELEVUNIT
0 - N
Defines input units for receptor elevations (defaults to
meters), must be first keyword after RE STARTING if used.
GRIDCART
01 - R
Defines a Cartesian grid receptor network
GRIDPOLR
01 - R
Defines a polar receptor network
DISCCART
01 - R
Defines the discretely placed receptor locations referenced
to a Cartesian system
DISCPOLR
01 - R
Defines the discretely placed receptor locations referenced
to a polar system
EVALCART
01 - R
Defines discrete Cartesian receptor locations for use with
EVALFILE output option
FINISHED
M - N
Identifies the end of RECEPTOR pathway inputs
1) At least one of the following must be present: GRIDCART, GRIDPOLR,
DISCCART, DISCPOLR, or EVALCART. Multiple receptor networks can be
specified in a single run, including both Cartesian and polar, up to
an overall maximum controlled by the NREC parameter.
B-7
-------
TABLE B-6
DESCRIPTION OF RECEPTOR PATHWAY KEYWORDS AND PARAMETERS
Keyword
Parameters
ELEVUNIT
METERS or FEET
where:
METERS
FEET
Specifies input units for receptor elevations of
meters
Specifies input units for receptor elevations of feet
Note: This keyword applies to receptor elevations
only.
GRIDCART
Netid STA
XYINC
or XPNTS
YPNTS
ELEV
FLAG
END
Xinit Xnum Xdelta Yinit
Gridxl Gridx2 Gridx3 ....
Gridyl Gridy2 Gridy3 ....
Row Zelevl Zelev2 Zelev3
Row Zflagl Zflag2 Zflag3
Ynum Ydelta
GridxN, and
GridyN
.. ZelevN
. . Z flagN
where:
Netid
STA
XYINC
Xinit
Xnum
Xdelta
Yinit
Ynum
Ydelta
XPNTS
Gridxl
GridxN
YPNTS
Gridyl
GridyN
ELEV
Row
Zelev
FLAG
Row
Z flag
END
Receptor network identification code (up to eight
alphanumeric characters)
Indicates STArt of GRIDCART subpathway, repeat for
each new Netid
Keyword identifying grid network generated from
x and y increments
Starting local x-axis grid location in meters
Number of x-axis receptors
Spacing in meters between x-axis receptors
Starting local y-axis grid location in meters
Number of y-axis receptors
Spacing in meters between y-axis receptors
Keyword identifying grid network defined by a series
of x and y coordinates
Value of first x-coordinate for Cartesian grid
Value of 'nth' x-coordinate for Cartesian grid
Keyword identifying grid network defined by a series
of x and y coordinates
Value of first y-coordinate for Cartesian grid
Value of 'nth' y-coordinate for Cartesian grid
Keyword to specify that receptor elevations follow
Indicates which row (y-coordinate fixed) is being
input
An array of receptor terrain elevations for
a particular Row
Keyword to specify that flagpole receptor heights
follow
Indicates which row (y-coordinate fixed) is being
input
An array of receptor heights above local terrain
elevation for a particular Row (flagpole receptors)
Indicates END of GRIDCART subpathway, repeat for each
new Netid
B-8
-------
TABLE B-6 (CONT.)
DESCRIPTION OF RECEPTOR PATHWAY KEYWORDS AND PARAMETERS
GRIDPOLR
Netid STA
ORIG Xinit Yinit,
or ORIG Srcid
DIST Rincrl Rincr2 Rincr3 . . . RinaN
DDIR Dirl Dir2 Dir3 ... DirN,
or GDIR Dirnum Dirini Dirinc
ELEV Dir Zelevl Zelev2 Zelev3 ... ZelevN
FLAG Dir Zflaal Zflaa2 Zflaa3 ... ZflaaN
END
where:
Netid
Receptor network identification code (up to eight
alphanumeric characters)
STA
Indicates STArt of GRIDPOLR subpathwav, repeat for
each new Netid
ORIG
Optional keyword to specify the origin of the polar
network (assumed to be at x=0, y=0 if omitted)
Xinit
local x-coordinate for origin of polar network (m)
Yinit
local y-coordinate for origin of polar network (m)
Srcid
Source ID of source used as origin of polar network
DIST
Keyword to specify distances for the polar network
Ringl
Distance to the first ring of polar coordinates (m)
RingN
Distance to the 'nth' ring of polar coordinates (m)
DDIR
Keyword to specify discrete direction radials for the
polar network
Dirl
First direction radial in degrees (1 to 360)
DirN
The 'nth' direction radial in degrees (1 to 360)
GDIR
Keyword to specify generated direction radials for
the polar network
Dirnum
Number of directions used to define the polar system
Dirini
Starting direction of the polar system
Dirinc
Increment (in degrees) for defining directions
ELEV
Keyword to specify that receptor elevations follow
Dir
Indicates which direction is being input
Zelev
An array of receptor terrain elevations for a
particular direction radial
FLAG
Keyword to specify that flagpole receptor heights
follow
Dir
Indicates which direction is being input
Z flag
An array of receptor heights above local terrain
elevation for a particular direction (flagpole
receptors)
END
Indicates END of GRIDPOLR subpathwav, repeat for each
new Netid
B-9
-------
TABLE B-6 (CONT.)
DESCRIPTION OF RECEPTOR PATHWAY KEYWORDS AND PARAMETERS
DISCCART
Xcoord Ycoord (Zelev) (Zflag)
where:
Xcoord
Ycoord
Zelev
Z flag
local x-coordinate for discrete receptor location (m)
local y-coordinate for discrete receptor location (m)
Elevation above sea level for discrete receptor
location (optional), used onlv for ELEV terrain
Receptor height (flagpole) above local terrain
(optional), used onlv with FLAGPOLE kevword
DISCPOLR
Srcid Dist Direct (Zelev) (Zflag)
where:
Srcid
Dist
Direct
Zelev
Z flag
Specifies source identification for which discrete
polar receptor locations apply (used to define the
origin for the discrete polar receptor)
Downwind distance to receptor location (m)
Direction to receptor location, in degrees clockwise
from North
Elevation above sea level for receptor location
(optional), used onlv for ELEV terrain
Receptor height (flagpole) above local terrain
(optional), used onlv with FLAGPOLE kevword
EVALCART
Xcoord Ycoord Zelev Zflag Arcid (Name)
where:
Xcoord
Ycoord
Zelev
Z flag
Arcid
(Name)
local x-coordinate for discrete receptor location (m)
local y-coordinate for discrete receptor location (m)
Elevation above sea level for discrete receptor
location (optional), used onlv for ELEV terrain
Receptor height (flagpole) above local terrain
(optional), used onlv with FLAGPOLE kevword
Receptor arc ID used to group receptors along
an arc or other grouping (up to eight characters)
Optional name for receptor (up to eight characters)
B-10
-------
TABLE B-7
DESCRIPTION OF OUTPUT PATHWAY KEYWORDS
OU Keywords
Type
Keyword Description
STARTING
M - N
Identifies the start of OUTPUT pathway inputs
RECEPTOR
M - N
Identifies the output filename for receptor data
SOURCLOC
0 - N
Identifies the output filename for source location data
FINISHED
M - N
Identifies the end of OUTPUT pathway inputs
B-ll
-------
TABLE B-8
DESCRIPTION OF OUTPUT PATHWAY KEYWORDS AND PARAMETERS
Keyword
Parameters
RECEPTOR
Reefil
where:
Reefil
Specifies output filename for receptor data (up to 60
characters)
SOURCLOC
Srcfil
where:
Srcfil
Specifies output filename for source location data (up
to 60 characters)
B-12
-------
APPENDIX C. EXPLANATION OF ERROR MESSAGE CODES
C.l INTRODUCTION
The AERMAP preprocessor uses a "defensive programming" approach to eliminate as much as
possible of the user's work in debugging the input runstream file. Also, a great deal of effort has been
made to eliminate the possibility of run time errors, such as "divide by zero," and to point out
questionable input data.
Message Summary: The AERMAP preprocessor outputs a summary of messages to the
message file specified on the command line. This message table gives the number of messages of
each type, together with a detailed list of all the fatal errors and warning messages. During setup
processing, if no errors or warnings are generated, then the program simply reports to the user that
"SETUP Finishes Successfully."
C.l THE OUTPUT ERROR LOG MESSAGE SUMMARY
There are two message summaries provided in the message file generated by the AERMAP
preprocessor. The first one is located after the echo of input runstream file images. This summary
will take one of two forms, depending on whether any fatal error or non-fatal warning messages were
generated, and also depending on whether the option to RUN or NOT to run was selected on the CO
RUNORNOT card. If there are no errors or warnings generated during the setup processing, and the
RUN option was selected, then the program simply reports that "SETUP Finishes Successfully." If
any fatal errors or warning messages were generated during the setup processing, or if the option
NOT to run was selected, then a more detailed summary is provided. This summary provides a
message count for each type of message, and a detailed listing of each fatal error and warning message
generated. The second message summary table is located at the very end of the message file, and it
sums up the messages generated by the complete preprocessor run - both setup processing and
run-time processing.
C-l
-------
An example of a setup processing message summary is shown in Figure C-l.
*** Message
Summary For The AERMAP Preprocessor Setup ***
Summary of Total Messages
A
Total of
0 Fatal Error Message(s)
A
Total of
0 Warning Message(s)
A
Total of
0 Information Message(s)
FATAL ERROR MESSAGES ********
*** NONE ***
WARNING MESSAGES ********
*** NONE ***
*** SETUP Finishes Successfully ***
FIGURE C-l. EXAMPLE OF AN AERMAP MESSAGE SUMMARY
C.3 DESCRIPTION OF THE PET ATT,ED MESSAGE LAYOUT
Two types of messages can be produced by the program during the processing of input
runstream images and during preprocessor calculations. These are described briefly below:
Errors that will halt any further processing, except to identify additional error
conditions (type E); and
Warnings that do not halt processing but indicate possible errors or suspect conditions
(type W).
The messages have a consistent structure which contains the pathway ID, indicating which
pathway the messages are generated from; the message type followed by a three-digit message
number; the line number of the input runstream image file for setup messages; the name of the module
(e.g. the subroutine name) from which the message is generated; a detailed message corresponding to
the message code; and an 8-character simple hint to help the user spot the possible source of the
problem.
C-2
-------
The following is an example of a detailed message generated from the CO pathway:
CO E100 8 EXPATH: Invalid Pathway Specified. The Troubled Pathway is FF
The message syntax is explained in more detail below (values in parentheses give the column numbers
within the message line for each element):
Message type (E, W, I) (4:4)
Pathway ID (CO or RE) (1:2)
Detailed message for this code (22:71)
Numeric message code (a 3 digit number) (5:7)
PWTxxx LLLL mmmmmm: MESSAGE Hints
Name of the code module from which the
message is generated (14:19)
The line number of the input runstream image
file where the message occurs (9:12)
Hints to help you determine the nature
of errors (keyword, pathway where the
error occurs,...etc.) (73:80)
The two message types are identified with the letters E (for errors) and W (for warnings). A detailed
description of each of the message codes currently used in the program is provided in the next section.
C-3
-------
C.4 DETAILED DESCRIPTION OF THE ERROR/MESSAGE CODES
INPUT RUNSTREAM IMAGE STRUCTURE PROCESSING
This type of message indicates problems with the basic syntax and/or structure of the input
runstream image. Typical messages include errors like "Missing mandatory keyword", "Illegal
Keyword", ..., etc. If a fatal error of this kind is detected in a runstream image, a fatal error message is
written to the message file and any attempt to process data is prohibited, although the remainder of the
runstream file is examined for other possible errors. If a warning occurs, data may still be processed,
although the inputs should be checked carefully to be sure that the condition causing the warning does
not indicate an error.
100 Invalid Pathway Specified. The pathway ID should be a 2 character string. It should be one of
the following: CO for control pathway or RE for receptor pathway. Its position is normally
confined to columns 1 and 2 (1:2) of the input runstream file. However, the program does
allow for a shift of the entire input runstream file of up to 3 columns. If the inputs are shifted,
then all input records must be shifted by the same amount. The invalid pathway is repeated at
the end of the message.
105 Invalid Keyword Specified. The keyword ID should be an 8-character string. Its position is
normally confined to columns 4 to 11 (4:11) of the input runstream file. However, the program
does allow for a shift of the entire input runstream file of up to 3 columns. If the inputs are
shifted, then all input records must be shifted by the same amount. There should be a space
between keyword ID and any other data fields. For a list of valid keywords, refer to Appendix
A or Appendix B. The invalid keyword is repeated at the end of the message.
110 Keyword is Not Valid for This Pathway. The input keyword is a valid 8-character string, but it
is not valid for the particular pathway. Refer to Appendix A, Appendix B or Section 3 for the
correct usage of the keyword. The invalid keyword is repeated at the end of the message.
115 Starting and Finishing Statements do not match. Only One STARTING and one FINISHED
statement, respectively, is allowed at the very beginning and the very end of each pathway
block. Check the position and frequency to make sure the input runstream file meets the
format requirement. The pathway during which the error occurs is included at the end of the
message.
120 Pathway is Out of Sequence. The pathways are not input in the correct order. The correct
order is CO, SO (optional), RE, and OU for the AERMAP preprocessor. The offending
pathway is given as a hint.
125 Missing FINISHED Statement - Runstream file is incomplete. One or more FINISHED
statements are missing.
C-4
-------
130 Missing Mandatory Keyword. To run the program, certain mandatory keywords must present
in the input runstream file. For a list of mandatory keywords, see Appendix A or Appendix B.
For more detailed information on keyword setup, see the description of message code 105.
The missing keyword is included with the message.
135 Duplicate Non-repeatable Keyword Encountered. More than one instance of a non-repeatable
keyword is encountered. For a list of non-repeatable keywords, see Appendix A or Appendix
B. The repeated keyword is included with the message.
140 Invalid Order of Keyword. A keyword has been placed out of the acceptable order. The order
for most keywords is not critical, but the relative order of a few keywords is important for the
proper interpretation of the input data. The keyword reference in Section 3 identifies any
requirements for the order of keywords. The keyword that was out of order is included with
the message.
152 ELEVUNIT card must be first for this pathway. The ELEVUNIT card must be the first non-
commented card after STARTING when used on the RE pathway. This requirement is made
in order to simplify reviewing runstream files to determine the elevation units used for sources
and receptors.
153 Cannot use obsolescent CO ELEVUNIT card with RE ELEVUNIT card.
160 Duplicate ORIG Secondary Keyword for GRIDPOLR. Only one origin card may be specified
for each grid of polar receptors. The network ID for the affected grid is included with the
message.
170 Invalid Secondary Keyword for Receptor GRID. The network ID for the affected grid is
included with this message. Refer to Appendix B for the correct syntax of secondary keywords.
175 Missing Secondary Keyword END for Receptor Grid. The END secondary keyword is
required for each grid of receptors input by the user (keywords GRIDCART and GRIDPOLR).
It signals the end of inputs and triggers the processing of data for that particular network.
180 Conflicting Secondary Keyword for Receptor Grid. Two incompatible secondary keywords
have been input for the same grid of receptors, e.g. GDIR and DDIR for the keyword
GRIDPOLR, where GDIR specifies to generate directions with uniform spacing, and DDIR
specifies that discrete, non-uniform directions are being specified.
185 Missing Receptor Keywords. No Receptors Specified. Since none of the RE pathway
keywords are mandatory, a separate error check is made to determine if any of the RE
keywords are specified. At least one of the following keywords must be present: GRIDCART,
GRIDPOLR, DISCCART, DISCPOLR, or EVALCART.
C-5
-------
PARAMETER SETUP PROCESSING
This type of message indicates problems with processing of the parameter fields for the
runstream images. Some messages are specific to certain keywords, while others indicate general
problems, such as an invalid numeric data field. If a fatal error of this kind is detected in a runstream
image, a fatal error message is written to the message file and any attempt to process data is
prohibited, although the remainder of the runstream file is examined for other possible errors. If a
warning occurs, data may still be processed, although the inputs should be checked carefully to be sure
that the condition causing the warning does not indicate an error.
200 Missing Parameter(s). No options were selected for the indicated keyword. Check Appendix
B for the list of parameters for the keyword in question.
201 Not Enough Parameters Specified For The Keyword. Check if there are any missing
parameters following the indicated keyword. See Appendix B for the required keyword
parameters.
202 Too Many Parameters Specified For The Keyword. Refer to Appendix B or Section 3 for the
list of acceptable parameters.
203 Invalid Parameter Specified. The inputs for a particular parameter are not valid for some
reason. Refer to Appendix B or Section 3. The invalid parameter is included with the
message.
205 No Option Parameter Setting. Forced by Default to: No setting was specified for a particular
parameter. Refer to Appendix B or Section 3 for the correct parameter usage. The default
setting is specified with the message.
206 Two or more DEM types exist. Check IPLAN values. The program detected more than one
type of DEM file. As an example, the program found a 1-degree and a 7.5-minute DEM file.
The program can only have one type of DEM file.
207 No Parameters Specified. Default Values Used For. The keyword for which no parameters are
specified is included with the message. Refer to Appendix B or Section 3 for a discussion of
the default condition.
208 Illegal Numerical Field Encountered. The program may have encountered a non-numerical
character for a numerical input, or the numerical value may exceed the limit on the size of the
exponent, which could potentially cause an underflow or an overflow error.
209 Negative Value Appears For A Non-negative Variable. The affected variable name is provided
with the message.
212 END Encountered Without (X,Y) Points Properly Set. This error occurs during setting up the
grid of receptors for a Cartesian Network. This message may occur for example if
X-coordinate points have been specified without any Y-coordinate points for a particular
network ID.
C-6
-------
213 NOT USED CURRENTLY - ELEV Input Inconsistent With Option: Input Ignored.
214 ELEV Inputs Inconsistent With Option: Defaults Used. This message occurs when the user
does not input elevated terrain heights for receptors when the TERRHGTS option is
PROVIDED. The program assumes that the missing terrain heights are at 0.0 meters for those
receptors and proceeds with ELEV terrain modeling.
215 FLAG Inputs Inconsistent With Option: Input Ignored. This message occurs when the user
inputs receptor heights above ground for flagpole receptors when the FLAGPOLE keyword
option has not been specified. The input flagpole heights are ignored in the program
calculations.
216 FLAG Inputs Inconsistent With Option: Defaults Used. This happens when the user does not
input receptor heights above ground for flagpole receptors when the FLAGPOLE keyword
option has been specified. The program assumes that the missing flagpole heights are equal to
the default value specified on the CO FLAGPOLE card. If no default height is specified on the
FLAGPOLE card, then a default of 0.0 meters is assumed.
217 More Than One Delimiter In A Field.
218 Number of (X,Y) Points Not Match With Number Of ELEV Or FLAG. Check the number of
elevated terrain heights or flagpole receptor heights for the gridded network associated with
the indicated line number in the runstream file.
219 Number Of Receptors Specified Exceeds Maximum. The user has specified more receptors on
the RE pathway than the program array limits allow. This array limit is controlled by the
NREC PARAMETER specified in the AERMAP.INC file. The value of NREC is provided
with the message.
220 Missing Origin (Use Default = 0,0) In GRIDPOLR. This is a non-fatal warning message to
indicate that the ORIG secondary keyword has not been specified for a particular grid of polar
receptors. The program will assume a default origin of (X=0, Y=0).
221 Missing Distance Setting In Polar Network. No distances have been provided (secondary
keyword DIST) for the specified grid of polar receptors.
222 Missing Direction Setting In Polar Network. Missing a secondary keyword (secondary
keyword GRIR or DDIR) for the specified grid of polar receptors.
223 Missing Elevations or Flagpole Fields. No data fields have been specified for the indicated
secondary keyword.
224 Number of Receptor Networks Exceeds Maximum. The user has specified more receptor
networks of gridded receptors on the RE pathway than the program array limits allow. This
array limit is controlled by the NNET PARAMETER specified in the AERMAP.INC file. The
value of NNET is provided with the message.
225 Number of X-Coords Specified Exceeds Maximum. The user has specified more X-coordinate
values for a particular grid of receptors than the program array limits allow. This array limit is
controlled by the IXM PARAMETER specified in the AERMAP.INC file. The value of IXM
is provided with the message.
C-7
-------
226 Number of Y-Coords Specified Exceeds Maximum. The user has specified more Y-coordinate
values for a particular grid of receptors than the program array limits allow. This array limit is
controlled by the IYM PARAMETER specified in the AERMAP.INC file. The value of IYM
is provided with the message.
227 No Receptors Were Defined on the RE Pathway. Either through lack of inputs or through
errors on the inputs, no receptors have been defined.
228 Default(s) Used for Missing Parameters on Keyword. Either an elevated terrain height or a
flagpole receptor height or both are missing for a discrete receptor location. Default value(s)
will be used for the missing parameter(s).
229 Too Many Parameters - Inputs Ignored on Keyword. Either an elevated terrain height or a
flagpole receptor height or both are provided when the corresponding option has not been
specified. The unneeded inputs are ignored.
232 Number of Specified Sources Exceeds Maximum. The user has specified more sources than
the array limits allow. This array limit is controlled by the NSRC PARAMETER specified in
the AERMAP.INC file. The value of NSRC is provided with the message.
250 Duplicate XPNT/DIST or YPNT/DIR Specified for GRID. One of the grid inputs, either an
X-coordinate, Y-coordinate, polar distance range or polar direction, has been specified more
than once for the same grid of receptors. This generates a non-fatal warning message.
252 Duplicate Receptor Network ID Specified. A network ID for a grid of receptors (GRIDCART
or GRIDPOLR keyword) has been used for more that one network.
254 Number of Receptor Arcs Exceeds Maximum. The user has input more than the number of
receptors arcs specified by the NARC PARAMETER in the AERMAP.INC file. The value of
NARC is provided with the message.
SETUP DATA AND QUALITY ASSURANCE PROCESSING
This type of message indicates problems with the actual values of the parameter data on the
input runstream image. The basic structure and syntax of the input card is correct, but one or more of
the inputs is invalid or suspicious. These messages include quality assurance checks on various
preprocessor inputs. Typical messages will tell the consistency of parameters and data for the setup
and run of the program. If a fatal error of this kind is detected in a runstream image, a fatal error
message is written to the message file and any attempt to process data is prohibited. If a warning
occurs, data may or may not be processed, depending on the processing requirements specified within
the runsteam input data.
300 Receptor Not Inside Domain. This is a fatal error generated when one of the receptors
specified in the RE pathway lies outside the domain specified on the CO pathway. The
receptor number is given with the message.
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305
310
320
330
335
340
350
360
370
375
377
380
Source Not Inside Domain. This is a fatal error generated when one of the source locations
specified in the SO pathway lies outside the domain specified on the CO pathway. The source
number is given with the message.
Domain Coordinate is NOT Inside a DEM File. This is a fatal error generated when one of the
domain coordinates lies outside the range of data covered by the DEM files included on the
CO pathway.
DEM File Does Not Exist. This is a fatal error generated when one of the DEM data files
specified on the CO pathway is not found.
Receptor is Not Inside a DEM File. This is a fatal error generated when one of the receptors
lies outside all of the DEM files specified by the user. The receptor number is included with
the message.
Source is Not Inside a DEM File. This is a fatal error generated when one of the source
locations lies outside all of the DEM files specified by the user. The source number is
included with the message.
No Terrain File Adjacent to This One. This is a fatal error generated when one of the DEM
data files is found to not be adjacent to any of the other data files specified. The DEM file
number is reported, and the file number represents the order of the file in the runstream.
Number of Nodes Exceeds Maximum. The number of nodes specified for a given profile
exceeds the maximum number set by the MAXNOD parameter in AERMAP.INC. The profile
number is specified with the message.
Latitude Specified on DOMAINLL Exceeds 60 Degrees. This is a non-fatal warning message
issued if a latitude of greater than 60 degrees is specified for the domain on the DOMAINLL
card. It may indicate that the order of longitude and latitude are reversed on the input data.
DATATYPE Card Does Not Match DEM Data File. The message indicates that the type of
DEM data, as determined from the file header record, for the file number specified does not
match the type specified on the DATATYPE card.
Specified Source ID Has Not Been Defined Yet. The message indicates that the user attempts
to use a source ID on a keyword before defining this source ID on a SO LOCATION card. It
could indicate an error in specifying the source ID, an omission of a LOCATION card, or an
error in the order of inputs.
Duplicate LOCATION Card Specified for Source. There can be only one LOCATION card for
each source ID specified. The source ID is included with the message.
This Input Variable is Out-of-Range. The indicated value may be too large or too small. Use
the line number to locate the card in question, and check the variable for a possible error.
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RUNTIME MESSAGE PROCESSING, 400-499
This type of message is generated during the preprocessor run. Setup processing has been
completed successfully, and the message is generated during the performance of calculations. If a
fatal error of this kind is detected during model execution, a fatal error message is written to the
message file and any further processing of the data is prohibited. The rest of the data file(s) will be
read and quality assurance checked to identify additional errors. If a warning occurs, data will still be
processed.
410 Receptor Location Outside Range of Profiles. This is a non-fatal warning message indicating
that a receptor location falls near the edge of a 7.5-minute DEM file and is outside the range of
the data profiles. If receptor elevations are being extracted from the DEM data, the nodes from
the nearest profile are used for this receptor.
420 Source Location Outside Range of Profiles. This is a non-fatal warning message indicating
that a source location falls near the edge of a 7.5-minute DEM file and is outside the range of
the data profiles. If source elevations are being extracted from the DEM data, the nodes from
the nearest profile are used for this source.
INPUT/OUTPUT MESSAGE PROCESSING
This type of message is generated during the preprocessor input and output. Typical messages
will tell the type of I/O operation (e.g., opening, reading or writing to a file), and the type of file. If a
fatal error of this kind is detected in a runstream image, a fatal error message is written to the message
file and any attempt to process data is prohibited. If a warning occurs, data may or may not be
processed, depending on the processing requirements specified within the runsteam input data.
500 Fatal Error Occurs During Opening of the Data File. The file specified can not be opened
properly. This may be the runstream file itself, or one of the DEM input data files. This may
happen when the file called is not in the specified path, or an illegal filename is specified.
Refer to the line number included in the error message to identify which file caused the error.
If no errors are found in the filename specification, then this message may also indicate that
there is not enough memory available to run the program, since opening a file causes a buffer
to be opened which takes up additional memory in RAM.
505 File is Already in Use, Cannot be Opened. The specified data file is already in use and could
not be opened. This error may indicate that a duplicate data filename has been specified.
510 Fatal Error Occurs During Reading of the File. File type is incorrect, or illegal data field
encountered. Check the indicated file for possible problems. For a DEM data file, be sure that
file has been converted to a DOS-compatible format using the CRLF.EXE program (provided
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with the AERMAP package). As with error number 500, this message may also indicate that
there is not enough memory available to run the program if no other source of the problem can
be identified.
520 Fatal Error Occurs During Writing to the File. Similar to message 510, except that it occurs
during a write operation.
550 DEM File Conflict for Specified DEM File Number. This error indicates a conflict in the
specification of DEM data files. It may be caused by entering a duplicate filename for a DEM
file.
580 End-of-File Reached Trying to Read a Data File. The AERMAP preprocessor has
unexpectedly encountered an end-of-file trying the read the indicated file. Check the data file
for the correct filename.
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TECHNICAL REPORT DATA
(Please read Instructions on reverse before completing)
1. REPORT NO.
EPA-454B-03-003
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Users Guide for the AERMOD Terrain Preprocessor (AERMAP)
5. REORT DATE
October 2004
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
See below.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Emissions Monitoring and Analysis Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final technical report. Supplement A
14. SPONSORING AGENCY CODE
EPA/200/04
15. SUPPLEMENTARY NOTES
i6 abstract This document is a users guide for the terrain preprocessor component (called AERMAP)
for the air dispersion model called AERMOD. In addition to providing detailed instructions on how to set up
and run the preprocessor, there is a brief description of the technical approach on which AERMAP is based.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
AERMOD, AERMAP, TERRAIN, PREPROCESSOR
Air Pollution models
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (Report)
Unclassified
21. No of pages 107
20. SECURITY CLASS (Page)
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION IS OBSOLETE
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United States Office of Air Quality Planning and Standards Publication No. EPA-454/B-03-003
Environmental Protection Emissions Monitoring and Analysis Division October 2004
Agency Research Triangle Park, NC
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