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User's Guide for the AERMOD Terrain
Preprocessor (AERMAP)
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EPA-454/B-18-004
April, 2018
User's Guide for the AERMOD Terrain Preprocessor (AERMAP)
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Air Quality Assessment Division
Air Quality Modeling Group
Research Triangle Park, North Carolina
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Notice
This user's guide has been reviewed by the Office of Air Quality 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
Intel is a registered trademark of Intel 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 WinZip Computing, S.L., a Corel Company.
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Preface
The U. S. Environmental Protection Agency (EPA), in conjunction with the American
Meteorological Society (AMS), developed the 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 initial User's Guide for AERMAP was prepared by Pacific Environmental Services,
Inc., Research Triangle Park, North Carolina. The 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 was modified by Peter
Eckhoff of the U.S. Environmental Protection Agency, Research Triangle Park, North Carolina.
The cumulative addendum was added to the User's Guide by Amec Foster Wheeler Environment
& Infrastructure, Inc. under Contract Number GS-35F-0851R, Task Order No. EP-G15D-00208.
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
Section Page
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 2-2
2.1.2 Modeling domain 2-5
2.1.3 Sources and receptors 2-7
2.1.4 Terrain data files 2-9
2.2 Input elevation data 2-10
2.2.1 NED data 2-11
2.2.2 DEM data 2-12
2.3 Receptor elevations and handling of gaps 2-13
2.3.1 History of AERMAP development 2-13
2.3.2 Calculating receptor elevations and treatment of edge receptors 2-14
2.3.3 Gap receptors due to NAD conversions 2-16
2.4 Keyword/parameter approach 2-20
2.5 An example AERMAP input file 2-21
2.5.1 Selecting Preprocessing Options - CO Pathway 2-22
2.5.2 Specifying a receptor network - RE pathway 2-25
2.5.3 Specifying the output file - OU pathway 2-26
2.6 Running AERMAP 2-27
2.7 Memory management, storage limitations, and creating a new executable 2-31
3.0 Detailed keyword reference 3-1
3.1 Overview 3-1
3.2 Control pathway inputs and options 3-2
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3.2.1 Title information 3-2
3.2.2 Options for elevated terrain 3-3
3.2.3 Flagpole receptor height option 3-3
3.2.4 Terrain data type specifications 3-4
3,2,4,1 National Elevation Dataset data 3-5
3.2.5 Terrain data file names specifications 3-6
3.2.5.1 Option for checking contents of DEM files 3-6
3.2.5.2 Optional TIFF debug file and user-specified elevation units for NED data 3-8
3.2.6 Domain extent specifications 3-12
3.2.7 Anchor point specification 3-14
3.2.8 NADCON grid shift files 3-18
3.2.9 Debug output files 3-19
3.2.10 To run or not to run - that is the question 3-22
3.3 Source pathway inputs and options (optional) 3-23
3.3.1 Including source data from an external file 3-24
3.4 Receptor pathway inputs and options 3-25
3.4.1 Including receptor data from an external file 3-25
3.4.2 Defining networks of gridded receptors 3-26
3.4.2.1 Cartesian grid receptor networks 3-26
3.4.2.2 Polar grid receptor networks 3-32
3.4.3 Using multiple receptor networks 3-35
3.4.4 Specifying discrete receptor locations 3-36
3.4.5 Discrete Cartesian receptors 3-36
3.4.5.1 Discrete polar receptors 3-37
3.4.5.2 Discrete Cartesian receptors for EVALFILE output 3-38
3.5 Output pathway inputs and options 3-39
4.0 Technical description 4-1
4.1 Determining receptor hill height scales 4-1
4.2 Digital elevation model (DEM) data 4-2
4.3 Data manipulation of DEM files by AERMAP 4-10
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4.4 Determining receptor (source) elevations using DEM data 4-11
5.0 References 5-1
Appendix A. Alphabetical keyword reference A-1
Appendix B. Functional keyword/parameter reference B-l
Appendix C. Explanation of error message codes C-l
C.l Introduction C-l
C.2 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-3
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Figures
Figure Page
Figure 2-1. Relationship among DEM Files, Domain, Sources and Receptors 2-6
Figure 2-2. Relationship of Receptor Slope Line to DEM Terrain Nodes and DEM and Domain
Boundaries 2-6
Figure 2-3. Structure of 7.5-minute DEM Data Illustrating Potential for 'edge' Receptors, Adapted
from USGS (1998) 2-16
Figure 2-4. Depiction of Overlap and Void Areas Caused by Using DEM Files with Different
Datums 2-19
Figure 2-5. Example of an AERMAP Output File for the Sample Problem 2-31
Figure 3-1. Sample from HILL Debug Output File 3-41
Figure 3-2. Sample from the RecDetail Debug File for NAD Conversions and Domain Check.. 3-42
Figure 3-3. Sample from the RecNDem Debug File for Assigning Local DEM/NED File 3-43
Figure 3-4. Sample from the RecElv Debug File for Receptor Elevation Calculations 3-44
Figure 4-1. Structure of a 7.5-minute DEM Data File 4-3
Figure 4-2. Structure of a 1-degree DEM data file for the lower latitudes 4-5
Figure 4-2. Structure of a 1-degree DEM data file for the lower latitudes 4-5
Figure C-l. Example of an AERMAP Message Summary C-2
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Tables
Table Page
Table 3-1. List of TiffTags Processed by AERMAP for NED Data 3-9
Table 3-2. List of GeoKeys Processed by AERMAP for NED Data 3-10
Table 3-3. Datum Switches for Anchor Location 3-17
Table 4-1. DEM Data Elements - Logical Record Type A 4-6
Table 4-2. DEM Data Elements - Logical Record Type B (Data Record) 4-9
Table A-l. All Keywords Available in AERMAP A-2
Table B-l. Description of Control Pathway Keywords B-2
Table B-2. Description of Control Pathway Keywords and Parameters B-3
Table B-3. Description of Source Pathway Keywords B-6
Table B-4. Description of Source Pathway Keywords and Parameters B-7
Table B-5. Description of Receptor Pathway Keywords B-8
Table B-6. Description of Receptor Pathway Keywords and Parameters B-9
Table B-7. Description of Output Pathway Keywords B-12
Table B-8. Description of Output Pathway Keywords and Parameters B-13
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1.0 Introduction
The U. S. Environmental Protection Agency (EPA), in conjunction with the American
Meteorological Society (AMS), developed the AMS/EPA Regulatory Model (AERMOD) air
quality dispersion model. 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, was 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, some
basic concepts are presented followed by a brief tutorial demonstrating 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
and the DEM format are 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
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physics of 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 runstream, or control, file that directs the actions of AERMAP
through a set of instructions and options, and defines the receptor and source locations. The
structure and syntax of an AERMAP input runstream file is based on the same pathways and
keyword structures as in the control runstream files for AERMOD.
Second, AERMAP needs standardized computer files of terrain data. The data are
available in multiple distinct formats. First is the National Elevation Dataset (NED) data, the
seamless bare earth elevation layer of The National Map (http://nationalmap.gov/) that is
updated frequently. NED data is available for importing into widely used commercial
software packages in several formats such as ArcGrid, GridFloat, IMG (ERDAS IMAGINE),
BILS, and GeoTIFF. AERMAP reads NED data in GeoTIFF format only. This format is
explained in Section 2.2.1.
According to the geoCommunity1 web site, "The USGS National Elevation Dataset...
has been developed by merging the highest-resolution, best quality elevation data available
across the United States into a seamless raster format. 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 US and 1:63,360-scale DEM data for Alaska. The dataset provides seamless
coverage of the United States, HI, AK, and the island territories. NED has a consistent
1 http://data.aeocomm.com/readme/usda/nedlO.html
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projection (Geographic), resolution 1/3 arc second (10m) and elevation units (meters). The
horizontal datum is NAD83, except for AK, which is NAD27. The vertical datum is
NAVD88, except for AK, which is NAVD29. NED is a living dataset that is updated
bimonthly to incorporate the "best available" DEM data."
A second format is the older Digital Elevation Model (DEM) format which follows the
old USGS "Blue Book" standard (see Section 4.2). This format originally was the terrain data
format that was processed by AERMAP. AERMAP retains the capability to process the DEM
format.
For those who are interested, the Blue Book format is provided in Section 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 latitude and longitude coordinates. These data files have been
available through several commercial internet sites in the past but availability of the individual
quadrangles with this release of the user's guide may be limited.
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.
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 (e.g.
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
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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 [Defense Mapping Agency] (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 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 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.
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Another format available to the user is a text file of horizontal location and elevation
data, referred to as XYZ format in this user's guide. However, the data must first be converted
to the "Blue Book" DEM format. A program is provided on EPA's Support Center for
Regulatory Atmospheric Modeling (SCRAM) website to convert XYZ data to the proper
format readable by AERMAP.
Finally, there is the SDTS. According to the USGS, "[f]or most practical purposes,
SDTS is a 'defunct' concept. USGS no longer supports it, nor has produced anything in that
format for more than 15 years. There is not any format standard active today that... is
analogous to SDTS. [USGS] continue[s] to make the SDTS web page
(http://mcmcweb.er.usgs.gov/sdts/) available for technical and historical reference purposes
only2." While considered a 'defunct concept', DEM data in SDTS format can be purchased
from the geoCommunity web site (http://data.geocomm.com/dem/). For example, quadrangles
in the SDTS format can be purchased from the geoCommunity web site in a bundle for the
entire United States. However, if a user already has or obtains SDTS data and wants to use it
in AERMAP, the data first must be converted to the "Blue Book" format. A conversion
program is available on EPA's SCRAM web site for this purpose as well as on the
geoCommunity web site.
Of these various data formats and standards, AERMAP is programmed to read files in
NED format and the USGS Blue Book format (hereafter referred to the DEM format).
1.3 Computer hardware requirements
The AERMAP terrain preprocessor was developed using Fortran on an IBM-
compatible personal computer (PC), with current versions of the program Fortran 90
compliant. AERMAP has been designed and compiled to run on a PC with a Pentium class or
higher central processing unit (CPU)and Microsoft® Windows® operating system in a
command prompt window. The executable available from EPA's SCRAM web site was
2 Private communication, August 30, 2016.
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compiled using the Intel® Visual Fortran 64 compiler. However, the user should be able to
recompile AERMAP on other computer platforms such UNIX or Linux-based systems using
Fortran compiler software specific to that platform.
The amount of hard disk drive storage space required for a particular application will
depend on the number and type of raw terrain (NED or 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. With terabytes of storage available on personal computers, the storage of terrain files
and preprocessor execution should not be an issue.
As noted above, SDTS data needs to be converted to the DEM ("Blue Book") 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 SCRAM website at
https://www3.epa.gov/ttn/scram/models/aermod/aermap/demfilz.zip as part of the AERMAP
package.
The executable found on EPA's SCRAM website is compiled as a 64-bit executable
and therefore will not run on a 32-bit PC. To run on a 32-bit computer, the user will have to
recompile AERMAP as a 32-bit executable with an appropriate Fortran compiler.
As an example of the time required by AERMAP to process a large number of
receptors, about 8400 receptors over a 50 km x 40 km domain were processed in about 45
minutes on a 3.1 GHz Intel® Core ™ i3-2100 computer with 8 Gb of installed memory
running Microsoft Corporation's 64-bit Windows 7 Professional operating system.
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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 runstream (control) file and a short tutorial on
creating a simple AERMAP run.
2.1 Basic concepts
AERMAP supports two types of elevation input data: 1) DEM elevation data in the
USGS DEM format (USGS, 1998); and 2) NED3 data in GeoTIFF format (USGS, 2002). The
more traditional type of elevation data is DEM, whereas NED is a newer type of elevation data
that is actively quality assured and updated. While AERMAP can process both types of data
(beginning with version 09040), AERMAP does not support processing both data formats
(DEM and GeoTIFF) within a single application. Both DEM and NED data are available at
different horizontal resolutions and may be retrieved based on geographic coordinates (latitude
and longitude) or UTM coordinates, although standard NED data are expected to be in
geographic coordinates. AERMAP was specifically designed to process NED data accessible
through the USGS Multi-Resolution Land Characteristics Consortium
(http://www.mrlc.gov/)4. but the code has been developed to be as generic as reasonably
possible to accommodate elevation data in GeoTIFF format from alternative sources.
AERMAP does not support elevation data in GeoTIFF format based on non-UTM projections,
such as Albers Equal Area or Lambert Conformal projections. Since USGS elevation data sets
are continually being updated and a number of different options are currently available for
obtaining digitized elevations, users are encouraged to clearly document the original source of
elevation data used with AERMAP.
3 The seamless bare earth DEMs formerly called the National Elevation Dataset, or NED, have been renamed and
are one component of elevation in The National Map's 3D Elevation Program (3DEP). The term "NED" will
continue to be used throughout this manual.
4 Terrain data are available from USGS's The National Map (http://nationalmap.gov/elevation.html), but are not
available in GeoTIFF format from that site.
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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 60 zones numbered from 1 to 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 (Snyder, 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 WGS72, 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 same for AERMAP applications. Some common ellipsoid/reference
system names and the datums associated with them are:
1. CLARKE 1866
a. NAD27 datum
b. Old Hawaiin datum
c. PUERO RICAN datum
d. GUAM datum
2. WGS72
a. WGS72 datum
3. GRS80/WGS84
a. NAD83 datum
b. WGS 84 datum
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A location on Earth will have different coordinates depending upon the datum used to define
that location.
The reference datum for NED data is normally NAD83, although NED data for Alaska
may also be in NAD27. For NED data in GeoTIFF format, AERMAP will assume NAD83 if
the reference datum identified in the TIFF file is not recognized, as long as the NADA=0
option is selected on the ANCHORXY keyword (see Section 3.2.7). The reference datums for
USGS 1-degree DEM data are either WGS72 or WGS84, and 7.5-minute DEM data will be
referenced to either the NAD27 or NAD83 datum. While more recent DEM files include the
reference datum in the header record (logical record type A) of the data file (USGS, 1998),
older files may not include that information. For DEM files without reference datum
information, AERMAP will assume datums of WGS72 for 1-degree data and NAD27 for
7.5-minute data.
While there are some minor differences between the WGS72, WGS84, and NAD83
datums, these differences are considered inconsequential for AERMAP applications, and
AERMAP treats WGS72, WGS84, and NAD83 datums as equivalent. Therefore, the focus of
datum conversion in AERMAP is on the conversion of NAD27 coordinates to NAD83, and
vice versa.
Since the AERMAP program is designed to process receptor (and possibly source)
locations expressed in terms of Cartesian X- and Y-coordinates, such as UTM or plant
coordinates, it is important to emphasize that the conversion of geographic coordinates due to
different reference datums is only part of the process. The process of converting UTM
coordinates from one datum to another actually involves three steps. The first step is to convert
the UTM coordinates from the first datum to geographic coordinates based on the reference
ellipsoidfor that datum. The second step is to convert the geographic coordinates from the
first datum to the second datum to account for the datum shift. The final step is to convert the
new geographic coordinates back to UTM coordinates based on the reference ellipsoidfor the
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new datum. This process of converting coordinates between NAD27 and NAD83 is illustrated
in the following diagram:
The diagram also identifies the AERMAP subroutines used to perform each of the steps in the
process (the text below each arrow).
Versions of AERMAP prior to version 06341 only accounted for the middle step, or the
datum conversion, and did not account for the effect of different reference ellipsoids between
the two datums on the converted UTM coordinates. This typically accounts for an additional
shift of about 200m in the Northing coordinate between NAD27 and NAD83, with the NAD83
Northing coordinate being larger than the NAD27 coordinate. This additional horizontal shift
can result in significant discrepancies in calculated receptor elevations and critical hill heights,
even in areas with only moderate terrain relief.
In order to successfully apply the AERMAP program for cases involving NAD
conversions, the user should first be aware of the reference datum used to define the receptor
and source coordinates for that application, and know the reference datum(s) for the DEM
file(s) being processed. The user also needs to understand how AERMAP utilizes and
interprets the user-specified modeling domain (DOMAINXY or DOMAINLL keywords,
optional beginning with version 09040) and the user-specified anchor point (ANCHORXY
keyword). These keywords on the CO pathway are described in detail in Sections 3.2.6 and
3.2.7, respectively. The basic information is reiterated here, with some additional
clarifications. Changes to the DOMAINLL keyword introduced with version 09040 are also
described. The following sections also document the assumptions incorporated into AERMAP
for applications where the DEM file NAD is not identified, and provide suggestions for cases
where the user is not certain of the reference datum for receptor and source coordinates being
input to AERMAP.
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2.1.2 Modeling domain
A modeling domain is the geographic extent that includes all the receptors and sources
specified in a particular AERMAP run. The domain also defines the region of significant terrain
elevations within which the terrain data points are included in the calculation of hill height
scales. Specification of a domain with either of the keywords DOMAINXY or DOMAINLL in
AERMAP is optional but can serve two possible functions:
1. in rare situations involving prominent terrain features (e.g., Mount Rainier) which
would be selected as the hill height scale beyond a reasonable range of influence, the
domain options can be used to exclude such features from the analysis; and/or
2. to optimize the AERMAP runtime by excluding portions of the terrain inputs that
can reasonably be assumed to have no influence on hill height scales for the specified
receptor network.
Unless the first situation is known to be of concern for a specific application, omitting
the domain specification will simplify the AERMAP setup in most cases, without any adverse
impact on the results other than somewhat longer runtimes. A discussion and use of the
optional keywords DOMAINXY and DOMAINLL is in Section 3.2.6.
If a domain is specified by the user, it can span over multiple UTM zones and multiple
adjacent DEM or NED files. The domain can be specified either in the UTM or the
latitude/longitude coordinate system depending on the keyword (DOMAINXY or
DOMAINLL). For DEM data, the preprocessor converts the domain coordinates to the units
of the DEM data, i.e., UTM when using 7.5-minute 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 2-1 illustrates the relationship among the DEM data files, the domain, and
receptors. A similar relationship would exist for one or more NED files.
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DEM File #1
DEM File#2
Domain Boundary
t
Source
Discrete & Gridded
Receptors |
¦ • m m
DEM File #2
DEM Fils #4
Figure 2-1. Relationship among DEM Files, Domain, Sources and Receptors
Significant terrain elevations include all the terrain that is at or above a 10% slope from
each and every receptor. Additional DEM files or increasing the extent of the NED file(s)
may be needed to perform these calculations. It is up to the user to assure all such terrain
nodes are covered. Figure 2-2 shows the relationship of the receptor slope line to DEM terrain
nodes for multiple DEM files. A similar figure would apply for one or more NED files.
DEM Fi e #1
DEM File #2
10%
When a DEM terrain node
breaks through the 10%
slope, additional DEM files
are required and the domain
needs to be expanded to
include this node.
DEM terrain nodes
excludable when
below 10% slope
Domain Boundary
Mandatory inclusion of DEM terrain nodes above
10% slope from each and every receptor.
Nodes must be inside Domain.
H I
Receptor
DEM File #3
DEM File M
Figure 2-2. Relationship of Receptor Slope Line to DEM Terrain Nodes and DEM and
Domain Boundaries
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During setup processing AERMAP checks all of the sources and receptors specified to
ensure that they are within the domain and within the area covered by the NED or 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 the NED or DEM files.
If the domain extends beyond the area covered by the terrain data, further processing
will continue provided no fatal error messages are generated from the above two conditions.
Smaller domains and fewer DEM files or smaller extents of the NED file(s) can decrease
processing time. Appropriate error messages are produced if the domain corners do not lie
within NED or DEM files or the receptors are outside the NED or DEM files.
2.1.3 Sources and receptors
Receptors are specified in AERMAP in a manner identical to the AERMOD dispersion
model, i.e., 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 in AERMAP (see Section 3.3).
All the source and receptor coordinates are referenced to a set of local coordinates
called ANCHOR coordinates that are referenced to a set of UTM coordinates. The datum of
the referenced UTM coordinates needs to be specified and will be used by the program to
align the various sources and receptors coordinates to the node coordinates of the individual
terrain 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, with no shifting of coordinates due to datum differences. Fourteen
conversion files for the 7.5 minute DEM data are available if "0" is not used. These files,
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discussed in detail in Section 3.2.8, 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 and NED data, AERMAP will check for zone changes in the
receptor network, and adjust the coordinates accordingly.
The user has the option of having AERMAP determine the terrain or base elevations
for the receptors from the terrain data or to provide the receptor elevations. This option is set
on the COntrol pathway. If the user requests AERMAP to determine the receptor base
elevations from the terrain 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 terrain nodes surrounding the receptor location (See 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 but does not specify the option on the CO
pathway to use the elevations from the NED or DEM terrain files, AERMAP will use the user-
provided elevations rather than extracting them from the digital data. Note that the terrain files
are required even if the user is providing the receptor heights because the terrain 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.
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2.1.4 Terrain data files
As discussed in Section 1.2, terrain data for AERMAP are available in multiple
formats. Currently, the primary format for terrain files is the NED format. When AERMAP
was first introduced, the DEM format was the most common format. The capability to process
DEM files has been retained in AERMAP. In addition to these formats, AERMAP can
process SDTS data and files of XYZ data (horizontal location and elevation). However, both
of these formats must be converted to DEM format for AERMAP to be able to use the terrain
data.
The user should note that formats change over time as well as web sites where data can
be obtained. The formats described in this user's guide and the web sites are current with this
release but may change in the future.
NED data can be obtained from the MRLC (http://www.mrlc.gov/) in GeoTiff format.
The appropriate 7.5-minute and 1-degree DEM file(s) and DEM data can be obtained from
commercial sites on the internet (e.g., http://data.geocomm.com/dem/demdownload.html).
The SDTS was being promoted by the USGS to eventually replace the old "native"
DEM files. As noted in Section 1.2, SDTS is a 'defunct' concept that USGS no longer
supports. The geoCommunity web site (www.geocomm.com) states that "The purpose of the
SDTS is to promote and facilitate the transfer of digital spatial data between dissimilar
computer systems, while preserving information meaning and minimizing the need for
information external to the transfer." The SDTS files are available on the internet (e.g.,
http://data.geocomm.com/dem/demdownload.html) and can be found zipped in a "tar" format.
Each SDTS file contains over a dozen native .DDF files that are used to reconstitute the SDTS
data back into the old "native" DEM format. Each of the DDF files starts with the same 4
digit string of the base SDTS file name. The "native" DEM format is read directly by
AERMAP. To reconstitute a DEM file: 1) unzip the SDTS file (most likely with a .gz
extension), 2) un-"tar" the files, 3) use SDTS2DEM to convert the SDTS files back to the
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native DEM format. Double click on the executable (in a Windows File Explorer
environment) and follow the prompts.
The NED and DEM data files are in a compressed format (e.g., with a .gz or .zip file
extension) and must be uncompressed with a utility that can work with these files. These
programs are widely available as shareware and freeware programs. One example is the
commercial software program WINZIP ® program from WinZip Computing. Another is the
freeware program 7-Zip. The uncompressed DEM file is a text file and does not include
record delimiters that are recognized by the Windows operating system, and therefore may not
be used directly with AERMAP. In early versions of AERMAP, for Windows users only, the
utility program CRLF.EXE added a carriage return and line feed to the end of each record in
the uncompressed DEM data file to create a DOS-compatible file. The current version of
AERMAP has eliminated the need to run this program on DEM files.
2.2 Input elevation data
Due to the potential for gaps to occur between adjacent DEM files as a result of NAD
conversions, users are encouraged to avoid using DEM files with different datums within the
same application if possible. Since NED elevation data are in a consistent reference datum and
horizontal resolution, the option introduced with version 09040 to process NED data instead of
DEM data has the advantage of avoiding potential issues associated with inconsistent datums
within the domain that may occur with DEM data.
Beginning with version 06341, the AERMAP program includes both mandatory and
optional (user-specified) debug output files. Three mandatory debug files provide general
information regarding the DEM or NED files and domain setup that may be useful in
documenting and resolving problems with the terrain files, AERMAP code, or with the setup
of the input data. Details on these files and the optional debug files are in Section 3.2.9
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2.2.1 NED data
Beginning with version 09040, AERMOD supports NED elevation data in the
GeoTIFF format, which is a binary file that includes data descriptors and geo-referencing
information in the form of "TiffTags" and "GeoKeys." AERMAP processes these TiffTags
and GeoKeys to determine the type and structure of the elevation data within the NED file.
NED elevation files can be obtained for user-specified domains through the USGS Multi-
Resolution Land Characteristics Consortium (http://www.mrlc.gov). Through this data
resource, the user defines a domain for downloading through various options, and can
download a single file to cover the entire modeling domain (up to 250 MB). The NED
elevation files are downloaded as compressed files, and the only file needed for input to
AERMAP is the file with the ".tif' file extension. NOTE: The default format for
downloading NED data from the MRLC is currently ArcGRID, which AERMAP cannot
read. The user must modify the file format to GeoTIFF before downloading the NED data
in order to use the data in AERMAP.
While the MRLC data server provides a mechanism to obtain data for the entire domain
in a single data file, AERMAP will accept multiple NED files in a single run. There is no
requirement for these files to be aligned according to a regular grid, similar to standard DEM
data. If multiple NED files overlap, which is likely in most cases, AERMAP will assign the
receptor to the first file encountered that contains the receptor for purposes of calculating
receptor elevations. As discussed above, AERMAP checks to determine whether higher
resolution elevation data are specified before lower resolution data in the AERMAP input file,
to ensure the receptor elevations are based on the highest resolution data provided. A warning
message will be generated if a lower resolution file is entered before a higher resolution file,
but processing will continue. However, a fatal error message will be generated if a receptor is
assigned to the lower resolution file within the region of overlap. The criteria for equivalence
in resolution between geographic and UTM data are listed in the previous section.
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2.2.2 DEM data
Versions of AERMAP prior to version 09040 were limited to only process one type of
DEM data a time, either the original 1-degree DEM (specified with a secondary keyword of
'DEMI') or the finer resolution 7.5-minute DEM data (specified as 'DEM7'). AERMAP now
allows for mixed DEM file inputs, including 1-degree and 7.5-minute DEM, as well as 15-
minute DEM data available for portions of Alaska. As a result of this modification the
secondary keyword has been changed to simply 'DEM'. Note that version 09040 of
AERMAP will ignore the additional qualifier of' 1' or '7' on the DEM data type used in
previous versions, allowing backward compatibility with older input files. The option for
mixed DEM file types allows for the use of the highest resolution data available for portions of
the modeling domain, with the lower resolution data to fill in the gaps in coverage that may
exist. For example, 7.5- minute DEM data are not available for quadrangles that are entirely
water. In these cases, 1-degree DEM files may be included to fill in these gaps within the
domain simplifying the application of AERMAP. However, AERMAP checks to determine
whether the higher resolution data files are listed first in the AERMAP input file to ensure that
receptor elevations will be based on the higher resolution data. For purposes of comparing the
resolution of data files, AERMAP assumes that the following resolutions are equivalent: l/9th
arc-second and 3 meters; 1/3rd arc-second and 10 meters; 1 arc-second and 30 meters; and 3
arc-seconds and 90 meters.
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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2.3 Receptor elevations and handling of gaps
In addition to correcting several issues associated with NAD conversions, beginning
with version 06341 the AERMAP program includes modifications to the procedure for
calculating receptor elevations and for handling receptors that may be located within gaps
between adjacent DEM files due to NAD conversions. The treatment and reporting of
receptors located within gaps was further refined with version 09040 of AERMAP.
2.3.1 History of AERMAP development
The original version of AERMAP, dating from the early-1990's, did not account for
NAD conversions since the early DEM data were based on consistent datums. The DEM data
format at that time did not even include a field for the reference datum. Receptor elevations in
the original version of AERMAP were also based on a 2-dimensional (bilinear) interpolation of
elevations from the four closest terrain nodes surrounding each receptor location. At that time,
the only complete DEM dataset for the continental U.S. was 1-degree data, where the node
profiles follow latitude and longitude lines parallel to, and including the edges of the DEM file.
While coverage of 7.5-minute DEM data was still limited at the time of the original AERMAP,
the issue of receptors that fall along the edges of the 7.5-minute DEM quadrangle beyond the
range of the node profiles was addressed by using the two closest nodes and flagging the
resulting elevation calculation as an edge receptor. Given the horizontal resolution of 30
meters for 7.5-minute DEM data at that time, this
When the AERMAP program was first modified to include a NAD conversion
capability to account for variations in reference datums, several changes were made to the
structure of the program to address some of the issues that arose, including the possibility of
receptors located in gaps between adjacent DEM files due to the NAD conversion. One of the
modifications was to use an inverse distance weighted average for the receptor elevation, based
on the closest four nodes in each quad (SW, NW, NE, and SE) relative to the receptor,
including nodes from adj acent DEM files. With the corrections to the NAD conversion
process, the potential magnitude of the gap between DEM files due to reference datums is
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limited to the datum shift only, and does not include the shift associated with the conversion
between UTM and geographic coordinates based on different ellipsoids. The magnitude of the
datum shift for NAD27 to NAD83 varies from about 10 meters or less over the Midwest
region, to about 30 to 40 meters along much of the Gulf coast region, to about 80 to 100 meters
in the Pacific Northwest region.
2.3.2 Calculating receptor elevations and treatment of edge receptors
The AERMAP program (beginning with version 06341) utilizes the original
2-dimensional (bilinear) interpolation method for calculating receptor elevations. This is a
relatively simple, well-documented method that is appropriate for interpolating between
regularly-spaced grid nodes, as in DEM or NED files. The bilinear interpolation has also been
specified as the standard method for interpolating elevations from digital terrain data by the
Federal Communications Commission (FCC, 1984). Some additional improvements have also
been incorporated into AERMAP for handling of edge receptors located beyond the range of
node profiles in 7.5-minute data, to account for proximity to nodes in both the Easting and
Northing directions for partial profiles that occur near the edges of the quadrangle (e.g.,
'Profiler and 'Profile n' shown in Figure 2-3). Beginning with version 09040, AERMAP
identifies the following four types of receptors, identified by the IERR code in subroutine
FIND4:
1. IERR = 0, normal, non-edge, receptor located within the range of profiles in both
the E-W and N-S directions, with elevations based on the four surrounding nodes;
2. IERR = -1, standard edge receptor no more than one Ax beyond the E-W range of
the first or last profile, and/or no more than one Ay beyond the N-S range of nodes
within the profiles (shown by solid arrows in Figure 2-1). AERMAP uses the
closest 1 or 2 nodes to calculate the receptor elevation in these cases, with no
adjustment for offsets in the y-direction from adjacent profiles;
3. IERR = -2, edge receptor no more than one Ax from the closest profile, but more
than one Ay beyond the vertical range of one of the profiles that straddle the
receptor (shown by the dashed arrow in Figure 2-1). AERMAP uses nodes from
the closest profile that spans the N-S location of the receptor;
4. IERR = -3, edge receptor more than one Ax beyond the E-W range of all profiles
and/or more than one Ay beyond the N-S range of all neighboring profiles. This
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condition indicates that an internal data gap exists along one or more edges of the
terrain file, and elevations for receptors in this category are suspect. This case
should not occur for standard DEM, and is not shown in Figure 2-1.
An internal data gap could occur as a result of converting elevations from one format to
another, such as from 1-degree DEM data to 7.5-minute DEM format, when NAD conversions
are involved. Due to the datum shift, the profiles from the original DEM file may not fully
cover the range of geographic coordinates specified for the converted file. These gaps will
typically occur along the northern edge of the converted file, and the gap may be over 200
meters wide. Depending on the process used to generate the converted file, the gap area may
be devoid of nodes or the area may be filled with nodes that are assigned a missing data code.
AERMAP generates warning message number 400 to flag these internal gap receptors, and
assigns a missing code of -9999.0 to the receptor elevation, unless the FILLGAPS option is
specified on the CO DATATYPE keyword (see Section 3.2.4). If the FILLGAPS option is
specified, and the gap has not been filled by nodes with missing values, then AERMAP will
assign a receptor elevation based on the closest nodes within the file and issue warning
message number 403. The FILLGAPS option will have no effect for files with internal gaps
that are filled by nodes with missing values, and the receptor elevation will be assigned a
missing code of -9999.0 in those cases. For applications with multiple overlapping DEM files,
AERMAP will attempt to calculate an elevation for these internal gap receptors from any
subsequent files that contain the receptor. An additional warning message (number 405) will
be generated if AERMAP finds a non-missing elevation for these receptors from a subsequent
file.
The IERR code for each receptor is identified in the optional RECELV debug output
file. The RECELV debug file provides useful data for investigating potential problems with
edge or gap receptors. With the introduction of finer resolution 10-meter 7.5-minute DEM
files in recent years, the representativeness of elevations for the first two types of edge
receptors is less of a concern. However, elevations for receptors located within internal gap
areas (with the FILLGAPS option) may be based on elevations from nodes located over 200
meters away, and may not adequately represent terrain in that area. Elevations for gap
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receptors using the FILLGAPS option should therefore be reviewed for accuracy and
representativeness before using them in AERMOD. The capability of processing NED
elevation data should eliminate the potential for edge and gap receptors in AERMAP
applications, and users are especially encouraged to update to NED elevation data for
applications that include gap receptors. Note that the discussion in this section also applies to
determination of source elevations in AERMAP
¦#
O
Pt 2 /'
I ERR = -1
I ERR = -2
IERR = -1
Pt 3
IERR = -1
Easting
Ax
Ay
O
~ =
30 meters {Easting)
30 motors {Northing)
Elevation point in adjacent
quadrangle
Elevation point
First point along profile
Corner of DEM polygon
17.5-minute quadrangle corner
(Example is a quadrangle west of
central meridian of UTM zone.)
Figure 2-3. Structure of 7.5-niinute DEM Data Illustrating Potential for 'edge'
Receptors, Adapted from USGS (1998)
2.3.3 Gap receptors due to NAD conversions
Coordinate conversions to account for non-uniform datums can result in gaps between
adjacent DEM files, ranging in size from a few meters in parts of the Midwest to around 100
meters in parts of the Pacific Northwest. Calculating elevations for receptors located within
these gaps is problematic, and the representativeness of these gap calculations may be
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questionable, especially for areas with larger gap distances and/or areas with more significant
terrain relief. Because of these concerns, users are encouraged to avoid using DEM files with
different datums within the same application, if possible. The capability of processing NED
elevation data should eliminate the potential for gap receptors associated with NAD
conversions in AERMAP applications, and users are encouraged to update to NED elevation
data for applications that include these NAD gap receptors. If a receptor located within a
NAD-shift gap is no more than one Ax or Ay from profiles within the closest file, then the
receptor will be treated the same as an edge receptor described in Section 2.3.2 for cases
flagged with IERR = -1 or IERR = -2. These cases will be identified in the RECELV debug
file. Otherwise, receptors located within these NAD-shift gaps are handled the same as
receptors located within internal gaps, as described in Section 2.3.2. The receptor elevations
will be assigned a missing code of -9999.0 unless the FILLGAPS option is specified. NAD
gap receptor elevations filled with the FILLGAPS option based on the closest nodes will be
flagged with warning message number 402.
While gaps between DEM files is the main concern, users should also be aware that
portions of DEM files may overlap due to datum conversions, mirroring the datum gap,
depending on the direction of the NAD conversion (NAD27 to NAD83 or vice versa) and
depending on which side of the DEM file the receptors are located. The effect of this DEM file
overlap is that elevations calculated for receptors located within the overlap region may vary
slightly depending on the order in which the DEM files are listed in the AERMAP input file,
since AERMAP will assign the receptor to the first DEM file that contains those coordinates.
The AERMAP program uses the following method for identifying and handling these
NAD gap receptors:
1. AERMAP loops through each receptor to locate its local DEM file, initially using
no distance tolerance on the location of the receptor relative to the edges of the
DEM file. For applications with standard USGS DEM data files that do not involve
NAD conversions this loop should uniquely assign each receptor to its local DEM
file.
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2. AERMAP issues a warning message identifying each receptor that is not located
within a DEM file based on this initial loop.
3. AERMAP performs a second loop for all unassigned (potential "gap") receptors
without applying the NAD shift. Any receptor that falls within the boundaries of a
DEM file on this second loop is flagged as a "gap" receptor due to a NAD shift.
AERMAP then loops through these "gap" receptors using a distance tolerance of one-
half the datum shift in each direction (lat/lon or UTM-N/UTM-E), in order to assign
the receptor to the closest DEM file.
4. AERMAP issues a fatal error message for any receptor that is not located within a
DEM file based on this second loop.
5. If no fatal errors are encountered, AERMAP will continue with calculating elevations
for all receptors, including gap receptors. If the distance between the NAD gap
receptor and the closest DEM file node is no greater than the node spacing (Ax or Ay)
for that file,then the elevation for that receptor is treated the same as a standard edge
receptor (see Section 2.3.2). Otherwise, receptors located in NAD-shift gaps are
handled the same as receptors located within gaps inside the DEM file boundaries
(flagged with IERR = -3), as discussed in Section 2.3.2, although separate warning
messages are generated for external NAD-shift gap receptors and receptors located
within internal gaps. Unless the FILLGAPS option is selected, AERMAP will assign
a missing code of -9999.0 for NAD- shift gap receptors.
Given the uncertainties regarding appropriate elevations for receptors located within the NAD-
shift gap, users are encouraged to check the results for gap receptors relative to topographic
maps of the area to ensure the representativeness of the elevations for use in AERMAP. As
discussed above, the use of NED elevation data is encouraged in these cases, and should
eliminate this problem.
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 included with 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
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are used to convert receptors and sources coordinates of the old datum of the areas mentioned
above to NAD83. The files are included with the AERMAP package on the SCRAM web site,
(http://www.epa. gov/ scramOO 1 /). N A DC ON is used only with the 7.5-minute DEM files.
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 2-4).
In DEM files, same node coordinates
On earth, different locations.
Overlap area between DEM files
with two different datums (eg NAD 27 & 83)
No DEM coverage (Void) area between DEM files
with two different datums (eg NAD 27 & 83)
Figure 2-4. Depiction of Overlap and Void Areas Caused by Using DEM Files with
Different Datuins
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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.
2.4 Keyword/parameter approach
The input runstream 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, 2018a).
The input runstream file is divided into four functional "pathways." These pathways
are identified by two-character identifiers at the beginning of each record in the runstream.
The pathways for AERMAP are:
CO - for specifying overall job COntrol options;
SO - for specifying the SOurce location information (optional);
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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 runstream 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.here 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.
2.5 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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2.5.1 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
TITLEONE
DATATYPE -
DATAFILE -
ANCHORXY-
RUNORNOT-
FINISHED -
Indicates the beginning of inputs for the pathway; this
keyword is mandatory on each of the pathways.
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).
specifies the type of raw terrain data being supplied to
the preprocessor.
Identifies the raw terrain files being supplied in this run.
Defines the relationship between the user-coordinate system
and the UTM coordinate system.
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.
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
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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
10m NAD27 NW Durham DEM Data File With NAD27 Anchor Point
DATATYPE
DEM
DATAFILE
NWDurham 10m.dem
DOMAINXY
683500.0 3990500.0 17 686500.0 3993500.0 17
ANCHORXY
0.0 0.0 685000.0 3992000.0 17 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.
Two types of raw terrain DATATYPE are allowed — the DEM data (both 7.5-minute
and 1-degree) and NED data. In this example, DEM data is being used, which is identified by
the parameter DEM. The optional 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 this
example, UTM coordinates are specified, with the southwest corner of the domain at 683500
Easting (E) and 3990500 Northing (N) in zone 17, while the northeast corner of the domain is
at 686500 E and 3993500 N in zone 17. NOTE: Since longitude increases from east to west
over North America, the domain is defined by the southwest and northeast corners when
DOMAINLL is used.
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As described above, 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 685000 E, 3922000 N in Zone 17. The
entered datum value is 1 which indicates the anchor point is reference 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. 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.
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2.5.2 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 POLl
POLl
STA
ORIG
0.0
0.0
POLl
DIST
100.
200.
300.
500.
1000.
POLl
GDIR
36
10.
10.
POLl
END
RE
FINISHED
The GRIDPOLR keyword can be thought of as a "subpathway," 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 subpathway. The order of secondary keywords within the
subpathway is not critical, similar to the primary pathways. Each image in this subpathway
must be identified with a network ID (up to eight alphanumeric characters), in this case it is
"POLl." The "POL1" coordinates are referenced back to the ANCHOR point. Multiple
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.
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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 and 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 3.4.2.2).
2.5.3 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:
OU STARTING
RECEPTOR AERMAP_NAD2 7_DEM.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).
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2.6 Running AERMAP
Now that we have a complete and error-free runstream input file, the preprocessor is
ready to run. 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 for all AERMAP versions 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. Note that for Linux or
Unix systems, where the filenames are case-sensitive, the default filenames are aermap.inp and
aermap.out
Beginning with version 18081, the user can also enter the input runstream input filename and
optionally, the output filename as well. These options can be used when the runstream input
file is not named AERMAP.INP and the output filename is not named AERMAP.OUT. If the
user enters the input runstream filename, then the output filename uses the prefix of the input
filename to name the output file. The command line to run the sample problem with optional
input and output filenames might look something like this on the PC:
C\:>AERMAP aermap inputJile
Or,
C:\>AERMAP aermap input Jile aemap outputJile
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The input and output filenames can be full or relative pathnames of the files, when they are in
different directories than the current working directory or just the filenames when they are
located in the current working directory
As described in Section 2.5.3, 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. When not
specifying the input file on the command line or not specifying a pathname for the input file,
the input file must be located in the directory in which the user is working, i.e. the current
working directory. The output file is written to the current working directory if the user is not
specifying a pathname for the output file. Assuming that the 7.5-minute DEM data need to be
converted to NAD83, the *.las and the *.los files are needed by the NADCON subroutine to
perform the conversion. Although there are 14 files (7 .las and 7 .los), only the .las and .los
files that correspond to the region for which AERMAP is being run may be needed. In the
example above, Durham, NC is in the continental United States so the conus.las and conus.los
files would be needed to convert the 7.5-minute datums to NAD 83. These files can be in the
same subdirectory as the AERMAP executable, in which case AERMAP will locate them, or
the NADGRIDS keyword can be used on the CO pathway to inform AERMAP where to find
the files. In this example, the files were in the same folder where the input data (runstream file
and DEM file) were located.
Note: If no conversion has to be performed, i.e., the 7.5-minute DEM files are already
NAD83, then the .las and .los files are not needed.
When AERMAP is executed, an update on the status of processing is displayed on the
computer 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
2-28
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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 system whether it be Windows, DOS, UNIX,
Linux, MAC, etc. Sometimes the meaning of the message is obvious. Sometimes they can be
obscure. The detailed description of the error messages in Appendix C may be useful in
determining the meaning and cause of the message.
The message file 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. 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
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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 2-5.
2-30
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¦A* "Jr
AERMAP -
VERSION
11103
08/23/16
16:19:20
¦A* "Jr
*7^* *7^*
10m NAD27 NW
Durham DEM
Data
File With
NAD 2 7
Anchor Point
¦A" "Jr
A total of
1 DEM
files
were used
A total of
1
80 receptors
were processed
¦A* "Jr
DOMAINXY
683500
.0 3990500.0 17 686500
0 3993500.0 17
ANCHORXY
o
o
o
o
685000.0 3992000.
0 17 1
¦A* "A*
Terrain height
s
rfere extracted
by default
RE
ELEVUNIT
METERS
GRIDPOLR
POL1
STA
POL1
ORIG 0.0
o
o
POL1
DIST 100
200. 300.
500
1000.
POL1
GDIR 36
10
10.
GRIDPOLR
POL1
ELEV
1
120.3
123. 8
128 . 5
140. 8
129. 6
GRIDPOLR
POL1
ELEV
2
122 . 1
126. 8
132 . 1
143. 8
131.3
GRIDPOLR
POL1
ELEV
3
123.3
130.2
132 . 3
140.4
126.2
GRIDPOLR
POL1
ELEV
4
124.2
131. 8
131.7
133.7
128 . 8
GRIDPOLR
POL1
ELEV
5
124 . 5
130.4
127.2
127 . 9
128 . 5
GRIDPOLR
POL1
ELEV
6
124 . 0
128 . 1
124 . 0
125.4
119.4
GRIDPOLR
POL1
ELEV
7
121. 9
124 . 4
121.5
121.5
105. 0
GRIDPOLR
POL1
ELEV
8
119.4
121.4
122 . 1
117 . 9
CO
GRIDPOLR
POL1
ELEV
9
117 . 4
117 . 5
122 . 0
117 . 5
104 . 5
GRIDPOLR
POL1
HILL
1
141. 0
130.3
141. 1
140. 8
129. 6
GRIDPOLR
POL1
HILL
2
132 . 0
131. 1
132 . 1
143. 8
131.3
GRIDPOLR
POL1
HILL
3
132 . 0
130.2
132 . 3
140.4
126.2
GRIDPOLR
POL1
HILL
4
132 . 0
131. 8
131.7
133.7
128 . 8
GRIDPOLR
POL1
HILL
5
132 . 0
130.4
131.3
127 . 9
128 . 5
GRIDPOLR
POL1
HILL
6
132 . 0
131. 8
124 . 0
125.4
122 . 0
GRIDPOLR
POL1
HILL
7
132 . 0
132 . 0
125.5
121.5
108 . 3
GRIDPOLR
POL1
HILL
8
141. 8
132 . 0
125. 9
117 . 9
CO
GRIDPOLR
POL1
HILL
9
142 . 0
140.3
122 . 0
117 . 5
113.3
GRIDPOLR
POL1
END
Figure 2-5. Example of an AERMAP Output File for the Sample Problem
2.7 Memory management, storage limitations, and creating a new executable
Beginning with version 09040, AERMAP dynamically allocates array storage at
runtime based on the number of receptors, sources, DEM or NED data files, and the maximum
number of rows and columns of data within the elevation files. As a result, application of
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AERMAP will only be limited by available memory. In general, AERMAP is not a very
memory-intensive application. However, the processing of NED elevation data involves
creating a two-dimensional, double-precision array to store the elevation data from the entire
file for processing, regardless of whether a domain has been specified. This can require a
significant amount of memory for a large NED file. For example, a NED file with 3,000 rows
and 3,000 columns of data (representing a domain of about 90 kilometers on a side at 1 arc-
second or 30 meter resolution) would require over 70 MB of memory (approximately = #rows
* #columns * 8bytes). A domain of about 100,000 meters on a side (50 kilometers in each
rd
direction from the center) at 1/3 arc-second resolution (about 10 meters) would require about
800 MB of memory. For applications with NED data for large domains at high resolution (10
meters or less), it may be advantageous to split up the domain into smaller files. Since
AERMAP allocates and deallocates the elevation array storage for each file as it is initialized,
this will reduce overall memory requirements. Using multiple NED files to cover the domain
of interest may also allow AERMAP to optimize the calculation of hill height scales (the most
time-consuming portion of AERMAP) by skipping some files completely.
If users want to store a large number of DEM or NED files, the only limitation may be
the computer's storage device capacity, e.g., a computer's hard drive. With modern day hard
drive sizes on the order of a terabyte or more, the storage of terrain files should not be an
issue. However, when designing a study and planning to download the required terrain data,
keep several things in mind. A NED file with 1 arc- second resolution for a study about 100
kilometers on a side requires about 55 MB of storage in the GeoTIFF format (plus about 75
Kb for several ancillary files) and 1/3 arc-second resolution for the same area requires nearly
500 MB of storage. 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. For an area
extending 50 kilometers from a source, approximately 80 to 90 7.5-minute DEM files are
needed.
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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 code. Batch files for recompiling the source code with the Intel® compiler as well as
the gfortran Fortran compiler are packaged with the source code on SCRAM.
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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
preprocessor. Parentheses around a parameter indicate that the parameter is optional for that
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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 TITLEONE Title2
Type:
TITLEONE - Mandatory, Non-repeatable
TITLETWO - Optional, Non-repeatable
The parameters Titlel and Title2 are character parameters of length200, which are read as
a single field from columns 13 to 200 of the input record. Only the first 68 characters are written
to the printed output file. 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
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
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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 required to specify the type of the raw terrain data being
provided to the AERMAP terrain processor. The syntax and type of the keyword are
summarized below:
Syntax: CO DATATYPE DEM or (FILLGAPS^)
or
CO DATATYPE NED
Type: Mandatory, Non-repeatable
where the secondary keyword DEM specifies that DEM elevation data will be used, and NED
specifies that NED elevation data (in the GeoTIFF format) will be used. The optional secondary
keyword for DEM data, FILLGAPS, affects the processing of elevations for sources and/or
receptors located within data gap areas. Without the FILLGAPS option, AERMAP will assign a
missing code of -9999.0 for receptors and sources located within these gap areas. Note that the
AERMOD dispersion model (up to version 07026) does not currently check for missing
elevation codes, and will therefore not correctly simulate impacts for these cases. The next
update to AERMOD will include a check for missing receptor elevations, and will issue fatal
error messages for each case. More details regarding AERMAP's handling of receptors located
within gaps is provided in Section 2.3. The FILLGAPS option is not available for the NED data
option since gap areas should not occur with the use of standard NED data.
Versions of AERMAP prior to version 09040 were limited to only process one type of
DEM data a time, either the original 1-degree DEM (specified with a secondary keyword of
'DEMI') or the finer resolution 7.5-minute DEM data (specified as 'DEM7'). AERMAP now
allows for mixed DEM file inputs, including 1-degree and 7.5-minute DEM, as well as 15-
3-4
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minute DEM data available for portions of Alaska. As a result of this modification the secondary
keyword has been changed to simply 'DEM'. Note that version 09040 of AERMAP will ignore
the additional qualifier of' 1' or '7' on the DEM data type used in previous versions, allowing
backward compatibility with older input files. The option for mixed DEM file types allows for
the use of the highest resolution data available for portions of the modeling domain, with the
lower resolution data to fill in the gaps in coverage that may exist. For example, 7.5-minute
DEM data are not available for quadrangles that are entirely water. In these cases, 1-degree
DEM files may be included to fill in these gaps within the domain simplifying the application of
AERMAP. However, AERMAP checks to determine whether the higher resolution data files are
listed first in the AERMAP input file to ensure that receptor elevations will be based on the
higher resolution data. For purposes of comparing the resolution of data files, AERMAP
assumes that the following resolutions are equivalent: l/9th arc-second and 3 meters; l/3rd arc-
second and 10 meters; 1 arc-second and 30 meters; and 3 arc-seconds and 90 meters.
3.2.4.1 National Elevation Dataset data
Beginning with version 09040, AERMOD supports NED elevation data in the GeoTIFF
format, which is a binary file that includes data descriptors and geo-referencing information in
the form of "TiffTags" and "GeoKeys." AERMAP processes these TiffTags and GeoKeys to
determine the type and structure of the elevation data within the NED file. NED elevation files
can be obtained for user-specified domains through the USGS National Map
(http://viewer.nationalmap.gov/launch/). Through this data resource, the user defines a domain
for downloading through various options, and can download a single file to cover the entire
modeling domain (up to 250 MB). The NED elevation files are downloaded as compressed files,
and the only file needed for input to AERMAP is the file with the ".tif" file extension. NOTE:
The default format for downloading NED data from the MRLC is currently ArcGRID, which
AERMAP cannot read. The user must modify the file format to GeoTIFF before downloading
the NED data in order to use the data in AERMAP.
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While the USGS data server provides a mechanism to obtain data for the entire domain in
a single data file, AERMAP will accept multiple NED files in a single run. There is no
requirement for these files to be aligned according to a regular grid, similar to standard DEM
data. If multiple NED files overlap, which is likely in most cases, AERMAP will assign the
receptor to the first file encountered that contains the receptor for purposes of calculating
receptor elevations. As discussed above, AERMAP checks to determine whether higher
resolution elevation data are specified before lower resolution data in the AERMAP input file, to
ensure the receptor elevations are based on the highest resolution data provided. A warning
message will be generated if a lower resolution file is entered before a higher resolution file, but
processing will continue. However, a fatal error message will be generated if a receptor is
assigned to the lower resolution file within the region of overlap. The criteria for equivalence in
resolution between geographic and UTM data are listed in the previous section.
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
If the specified file is not found on the computer, the program will generate a fatal error message.
3,2.5,1 Option for checking contents of DEM files
An earlier version of AERMAP (dated 04300) incorporated a subroutine (DEMCHK) that
performs detailed checks on the contents of each DEM file on a character-by-character basis.
These checks serve two purposes: 1) to determine the structure of each DEM file by looking for
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carriage-return (CR) and line-feed (LF) characters and other non-alphanumeric characters for
purposes of reading the file correctly; and 2) to document the contents of the DEM file for
informational and/or debugging purposes. Based on these checks each DEM file is identified as
either: 1) a continuous ASCII record file (with no CR or LF); 2) a file with record delimiters,
such as a UNIX file (with LF but no CR) or a standard DOS file (with both CR and LF); or 3) a
possible binary file (containing non-alphanumeric characters besides CR and LF). The AERMAP
program supports DEM files as continuous ASCII records or with UNIX or DOS delimited
records, but a fatal error message is generated if the third type is encountered. NOTE: The
inclusion of the DEMCHK routine in AERMAP has eliminated the requirement for users to
convert DEMfiles to the standard DOS format using the CRLF.EXE utility program.
The full file check conducted in subroutine DEMCHK could be time consuming for
applications with a large number of DEM files, and especially for 7.5-minute DEM files with 10
meter horizontal resolution due to the larger file sizes. In order to retain the capabilities of the
DEMCHK routine, but to expedite processing where detailed checks of DEM file contents are not
warranted, beginning with version 06341 the AERMAP program incorporates a more limited
DEM check as the default operation, with a user option to request a full DEM check on a file-by-
file basis. The limited DEM check performs the same processing as the full check, but is limited
to the first 10240 characters (equivalent to the first 10 records of a DEM file). This limited check
should be sufficient to identify the type of DEM file in order to successfully read the data. The
complete check can be requested as needed to provide additional documentation if problems are
encountered. Note that the check of DEM file contents is exited as soon as a valid record
delimiter (UNIX LF or DOS CR/LF) is encountered.
The option to request a full DEM check for a particular DEM file has been added to the
CO DATAFILE keyword. The syntax and type of the DATAFILE keyword for DEM data are:
Syntax:
CO DATAFILE DEM FileName (CHECK)
Type:
Mandatory, Repeatable
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where DEM FileName is the DEM data filename, and the optional CHECK parameter indicates
that the full DEM check will be performed for that file. The CHECK parameter is not case-
sensitive. The DEM filename can be up to 200 characters in length based on the default
parameters in AERMAP. Double quotes (") at the beginning and end of the filename can also be
used as field delimiters to allow filenames with embedded spaces.
3,2.5,2 Optional TIFF debug file and user-specified elevation units for NED data
Beginning with version 09040, AERMAP supports NED data in the GeoTIFF format.
Historically, TIFF (Tagged-Image File Format) files were used as an efficient way to store
information for graphical display. The utility of the TIFF file format was greatly expanded by
incorporating additional codes that provide geo-referencing information related to the data. Such
files are referred to as GeoTIFF files. Two types of codes are included in GeoTIFF files:
1) TiffTags, which include information regarding the structure of the data within the file,
including number of rows and columns, data organization (stripped or tiled), and data format
(integer or floating point); and 2) GeoKeys, which provide the geo-referencing information,
including the type of projection (geographic or UTM) and horizontal reference datum. There are
two TiffTags that serve as the link between the "raster space" of standard TIFF files and
geographic space of GeoTIFF files. These codes provide the reference data to convert raster
coordinates (row I, column J) to geographic or projected (UTM) coordinates, and the resolution of
the pixels (grid cells) included in the file. Tables 2-2 and 2-3, respectively, list the TiffTags and
GeoKeys that are processed by AERMAP. These tables identify whether the TiffTags and
GeoKeys are required, optional, or whether their status is conditional based on other codes. The
default values are specified for optional TiffTags and GeoKeys. All other TiffTags and GeoKeys
are currently ignored by AERMAP. More information regarding TIFF and GeoTIFF files is
provided in the specification documents (Aldus, 1992; and Ritter, N. and M. Ruth, 1995).
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Table 3-1. List of TiffTags Processed by AERMAP for NED Data
TiffTags
Tag ID
Description
Status
Comments
256
'ImageWidth'
Required
Number of columns
257
'ImageLength'
Required
Number of rows
258
'BitsPerSample'
Required
Must be 8, 16, 32, or 64 bits
259
'Compression'
Optional
Default = 1 (uncompressed)
273
'StripOffsets'
Conditional
Required for stripped data
274
'Orientation'
Optional
Default = 1 (row major starting from
upper left corner of file)
277
'SamplesPerPixel'
Optional
Default = 1
278
'RowsPerStrip'
Optional
Default = 1 strip with nRows
322
'TileWidth'
Conditional
Required for tiled data
323
'TileLength'
Conditional
Required for tiled data
324
'TileOffsets'
Conditional
Required for tiled data
339
'SampleFormat'
Optional
Default = 1 (unsigned integer)a
33550
'ModelPixel Scale'
Required
33922
'ModelTiePoint'
Required
a USGS NED data are expected to be in floating point format, but AERMAP will process all
formats.
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Table 3-2. List of GeoKeys Processed by AERMAP for NED Data
GeoKeys
Key ID
Description
Status
Comments
1024
'GTModelTypeGeoKey'
Required
Projected (UTM) or
Geographic (Lat/Lon)
1025
'GTRasterTypeGeoKey'
Required
2048
'GeographicTypeGeoKey'
Conditional51
2050
'GeogGeodeticDatumGeoK
Conditional51
2054
'GeogAngularUnitsGeoKey'
Optional
Default = degrees
2056
'GeogEllipsoidGeoKey'
Conditional51
3072
'Proj ectedC S TypeGeoKey'
Conditional
Required for Proj ected
GTModelType
3076
'ProjLinearUnitsGeoKey'
Optional
Default = meters
4099
'V erti calUnitsGeoKey'
Optional
Default = meters
a Either the GeographicType, GeogGeodeticDatum, or GeogEllipsoid GeoKey is required if
GTModelType is Geographic
Given the binary nature of GeoTIFF files, the contents of the file cannot be "read" by
standard text editors or word processors. AERMAP includes an option to generate a TIFF debug
file for each NED data file specified with the DATAFILE keyword. The TIFF debug file
includes a listing of all TiffTags and GeoKeys contained within the specified GeoTIFF file.
NOTE: While the GeoTIFF specifications provide a GeoKey for vertical elevation
units (GeoKey ID 4099), most NED files currently do not include this GeoKey. If the elevation
units GeoKey is missing, then AERMAP assumes that elevations are in units of meters based on
the USGS documentation for NED data (USGS, 2002). Since non-USGS elevation files in
GeoTIFF format have been encountered that are in units of feet rather than meters, but lack the
appropriate GeoKey to specify the units, AERMAP includes an option for the user to specify
elevation units on the DATAFILE keyword. The syntax and type of the DATAFILE keyword for
NED data are:
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Syntax:
CO DATAFILE NED FileName (TIFFDEBUG) (ElevUnit)
Type:
Mandatory, Repeatable
where the NED FileName parameter is the filename for the NED data in GeoTIFF format, the
optional TIFFDEBUG parameter indicates that the TIFF debug file will be generated for this
data file, and ElevUnits refers to the optional user-specified elevation units for the NED data.
The TIFFDEBUG parameter is not case-sensitive. The NED filename can be up to 200
characters in length based on the default parameters in AERMAP. Double quotes (") at the
beginning and end of the filename can also be used as field delimiters to allow filenames with
embedded spaces, and do not count toward the 200 character limit. Note that the TIFFDEBUG
option must be included in order to specify elevation units. AERMAP generates a hard-coded
filename for the optional TIFFDEBUG file(s) as follows: 'TiffDebugFile nnnnn.dbg', where
'nnnnn' is the NED file number based on the order listed in the input file. Also note that the
CHECK option available for DEM files is not applicable to NED data.
The options available for ElevUnits are FEET, DECIFEET, DECAFEET, METERS,
DECIMETERS, and DECAMETERS. AERMAP will also recognize hyphenated fields for the
deci- and deca- options, such as DECI-FEET. The ElevUnits parameter is not case-sensitive.
Users are cautioned not to use the option for specifying elevation units unless the correct units are
known with certainty. It is preferable to utilize the GeoKey available for documenting elevation
units within the GeoTIFF file (GeoKey ID 4099). The user-specified elevation units will only be
used if the NED file does not include the GeoKey for elevation units. If the NED file includes
the elevation units code and the user-specified units (meters or feet) or vertical resolution (defined
by the ModelPixelScale TiffTag, 33550) conflict with the data file, a fatal error will be issued. If
the elevation units code and user-specified units agree, then an informational message is
generated and processing continues. Note that most GeoTIFF elevation files specify a vertical
resolution ("pixel scale") of '0' through the ModelPixel Scale TiffTag, which is not meaningful
for elevation data. AERMAP interprets a vertical pixel scale of 0 as a vertical resolution of 1.0
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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 hill height scales for the receptors.
The DOMAINXY and DOMAINLL keywords are optional. If the DOMAINXY and
DOMAINLL keywords are omitted, AERMAP will use all of the available data within the input
data files in the calculation of the critical hill height scales.
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
or
CO DOMAINLL Lonmin
Ydmin
Zonmin
Xdmax Ydmax Zonmax
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. The UTM Northing coordinate for southern hemisphere
locations is a positive number relative to a value of 10,000,000 meters at the equator. Southern
hemisphere UTM coordinates are identified by a negative UTM zone.
Beginning with version 09040 of AERMAP, the standard convention of negative values
for West longitude is used within the AERMAP code and output files. Based on this convention,
for the DOMAINLL keyword, Lonmin and Latmin are the longitude and latitude in decimal
degrees for the lower left (southwest) corner of the domain; and Lonmax and Latmax are the
longitude and latitude in decimal degrees for the upper right (northeast) corner of the domain,
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consistent with the DOMAINXY keyword. Note that longitude is entered first, followed by
latitude. In order to maintain backward compatibility with older AERMAP input files, code has
been included within AERMAP to adjust the inputs for the DOMAINLL keyword if needed to
conform to the new convention of negative for West longitude. AERMAP will issue a warning
message in these cases and will print the adjusted DOMAINLL parameters in the main output file
(aermap.out) as well as in the receptor and source elevation output files.
There are a few aspects regarding AERMAP's interpretation of the domain that deserve
further explanation and clarification. First, while the user can specify the domain using either
geographic coordinates (latitude and longitude) or UTM coordinates, the exact shape and extent
of the domain will be based on the type of DEM or NED data used. When geographic data, such
as 1-degree DEM data and standard NED data, are processed, AERMAP interprets the domain
boundaries along lines of constant latitude and longitude consistent with the profiles and nodes
within the data file. Conversely, when UTM data, such as 7.5-minute DEM data, are processed,
AERMAP interprets the domain boundaries along lines of constant UTM Northing and Easting
coordinates (note that Alaska 7.5-minute DEM data may be in either UTM or geographic
coordinates). This means that the same DOMAINXY or DOMAINLL card will define slightly
different geographical areas depending upon the type of elevation data being processed. This
approach was taken in the initial design of AERMAP to simplify the process of extracting and
analyzing the portion of a DEM file that falls within the domain since the domain will parallel the
profiles of elevation nodes within the DEM file. The structure of the two types of DEM files is
described in more detail in Section 4.2 of the AERMAP User's Guide (EPA, 2018b), and in the
USGS DEM documentation (USGS, 1998). To avoid confusion or uncertainty regarding the
extent of the domain, users may wish to define the domain in a manner that is consistent with the
type of DEM data, i.e., use DOMAINXY with UTM data and DOMAINLL with geographic data,
although this is not a requirement. Beginning with version 09040, AERMAP also allows for
mixed DEM files (e.g., 7.5-minute and 1-degree) to be used in the same run. Since the file type
(geographic or UTM) may vary in these cases, AERMAP sets the "type" of data and shape of the
domain based on the first data file specified.
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Users should also be aware that the AERMAP program (beginning with version 06341)
has been revised to account for NAD shifts in defining the extent of the domain, if needed. To
accomplish this conversion AERMAP assumes that the domain coordinates are referenced to the
datum specified by the user on the ANCHORXY keyword, described in the next section. This
revision to AERMAP may result in AERMAP-generated errors related to the domain extent for
some AERMAP applications that ran "successfully" with versions prior to version 06341.
3.2.7 Anchor point specification
AERMAP uses a Cartesian (X,Y) grid system to define relative location of sources and
receptors in the East-West (X) and North-South (Y) directions. The ANCHORXY keyword is
used to relate the user-specified coordinate system for the source and receptor locations to the
UTM coordinate system, including specification of the reference datum for the source and
receptor coordinates. The user has the option of specifying the receptor locations on the RE
pathway in UTM coordinates or in some arbitrary user-specified coordinate system. For any
further processing of the terrain data, the AERMAP program needs to determine the location of
the receptors in UTM coordinates. This is accomplished using the ANCHORXY keyword by
specifying the coordinates of any specific geographic location relative to both the user-specified
coordinate system and the UTM coordinate system. The syntax and type of the keyword are
summarized below:
Syntax: CO ANCHORXY Xauser Yauser Xautm Yautm Zautm NAD A
Type: Mandatory, Non-repeatable
where Xauser and Yauser are the coordinates of any geographic location, such as the origin (0,0),
in the user coordinate system, and Xautm, Yautm and Zautm are the UTM Easting, Northing and
Zone coordinates for the same point. The UTM Easting and Northing coordinates are specified
in meters. As noted in Section 2.1.1, UTM Northing coordinates for the southern hemisphere are
referenced to a value of 10,000,000 meters at the equator, and the UTM zone is negative for the
southern hemisphere. All receptor and source locations are referenced to this anchor point. The
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NAD A parameter specifies the horizontal datum that was used to establish the UTM coordinates
of the anchor point. NADA values range from 0 to 6, and are described below.
AERMAP uses the difference between the specified "user" coordinates (Xauser and
Yauser) and the UTM coordinates (Xautm and Yautm) to adjust the receptor coordinates
included on the RE pathway (and optional source coordinates on the SO pathway) to full UTM
coordinates. If the user specifies the receptor locations in UTM coordinates with the same UTM
zone and reference datum as the anchor point, then the coordinates provided on the
ANCHORXY keyword are arbitrary, as long as the values of Xauser and Xautm are identical,
and the values of Yauser and Yautm are identical.
Table 3-3 provides a list of applicable NADA values and the horizontal datum that each
NADA value references. These values follow the convention used in the USGS Standards for
Digital Elevation Models (USGS, 1998), and the list also follows the convention used in the
DEM file headers (logical record type A), except for the use of '0' (zero) to bypass the NAD
conversion. Note that the terms 'ellipsoid' and 'spheroid' are often used interchangeably in the
literature.
Based on the user-specified datum for the anchor point (NADA) and the datum code read
from each DEM or NED file, AERMAP will apply the appropriate adjustment to receptor, source
and domain coordinates to account for the shifts due to reference datums and reference
ellipsoids. The National Geodetic Survey program, North American Datum Conversion
(NADCON), version 2.1, has been incorporated into AERMAP and is used to calculate the
datum shifts. The NADCON program requires additional parameter files containing the grid
shift information. These grid shift files have *.las and *.los extensions, and files covering the
contiguous U.S. (CONUS), Hawaii, Puerto Rico/Virgin Islands, Alaska and three Alaskan Island
Groups (St. George, St. Paul, and St. Lawrence) are packaged with the AERMAP executable file.
When datum shifts are required for a particular AERMAP application, the appropriate grid shift
files (*.las and *.los) need to be included in the same folder as the AERMAP input file, unless
the optional NADGRIDS keyword on the CO pathway is used to specify a separate pathname for
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the NADCON grid shift files (see Section 3.2.8 for more details regarding this optional
keyword). AERMAP will issue a fatal error message if the necessary files are not found. Note
that the grid shift files are only required if a NAD conversion is needed based on the specified
NADA and reference datums among the input terrain files, and only the files needed for the
domain of a particular application (such as 'conus.las' and 'conus.los' for the contiguous U. S.)
are required. The grid shift files are not required when a NADA value of '0' is specified on the
ANCHORXY card. While a NADA value of '0' can be specified to avoid the NAD conversion
for AERMAP applications outside the United States where the grid shift files are not available, it
is preferable to specify the appropriate reference datum if it can be determined. Most
international terrain data bases will be referenced to either the WGS72 or the WGS84 datum,
with WGS84 being more likely for recent data. Since AERMAP treats WGS72 and WGS84 as
equivalent, the issues associated with datum conversion may not be very critical for non-US
applications.
If the user is unsure regarding the reference datum for the receptors (and sources) to be
used in a particular application, then the following suggestions may be helpful. Given the
potential significance of NAD shifts on receptor elevation and hill height scale results, the user is
first encouraged to make every effort to document the reference datum, perhaps by contacting the
original provider of the information. When no reliable information is available regarding the
datum, then the following assumptions are recommended. If the coordinates are from a previous
application that dates back several years (mid-1990's or earlier) or are likely to have been derived
from printed USGS 7.5-minute (1:24,000 scale) topographic maps, then the best recommendation
is to assume NAD27 as the reference datum. On the other hand, if the coordinates are from a
recent application and are likely to have been derived from a global positioning system (GPS)
device or a geographic information system (GIS), then the reference datum is more likely to be
NAD83. Note that topographic maps available on the Internet will generally plot coordinates
based on the NAD83 datum by default, but may also be able to plot coordinates in the NAD27
datum.
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Table 3-3. Datum Switches for Anchor Location
NADA
Description
0
No conversion is performed between NAD 27 and NAD 83 for the DEM nodes,
receptors, sources, or domain. This option may be used for international applications
where NAD shift grid files are not available. However, the reference datum used to
define the coordinates on ANCHORXY keyword should match the datum for terrain
data. Recent non-US terrain data is likely based on WGS84 datum.
While datum conversions are not performed with this option, conversion of UTM to
geographic coordinates for receptors, sources and domain within AERMAP will be
based on the appropriate ellipsoid for each data file. If the datum is not specified in
the data file, AERMAP defaults to the Clarke 1866 ellipsoid for 7.5-minute DEM files
and the GRS80 ellipsoid for 1-degree DEM files. If datum for NED data is not
specified or not supported by AERMAP, the GRS80 ellipsoid will be used by default.
1
North American Datum of 1927, NAD27, based on Clarke 1866 ellipsoid.
AERMAP accounts for shift from NAD27 to NAD83, as needed, for DEM nodes,
receptors, sources, and domain.
2
World Geodetic System of 1972 datum, WGS72, based on WGS72* ellipsoid.
AERMAP accounts for shift from WGS72 to NAD27, as needed, for DEM nodes,
receptors, sources, and domain.
3
World Geodetic System of 1984 datum, WGS84, based on WGS84* ellipsoid.
AERMAP accounts for shift from WGS84 to NAD27, as needed, for DEM nodes,
receptors, sources, and domain.
4
North American Datum of 1983, NAD83, based on GRS80* ellipsoid.
AERMAP accounts for shift from NAD83 to NAD27, as needed, for DEM nodes,
receptors, sources, and domain.
5
Old Hawaii Datum, based on Clarke 1866 ellipsoid, but not NAD 27.
AERMAP accounts for shift from the Old Hawaii Datum to NAD83, as needed, for
DEM nodes, receptors, sources, and domain.
6
Puerto Rico/Virgin Island Datum, based on Clarke 1866 ellipsoid, but not NAD 27.
AERMAP accounts for shift from the Puerto Rico/ Virgin Island Datum to NAD83, as
needed, for DEM nodes, receptors, sources, and domain.
* The GRS80 and WGS84 ellipsoids are considered to be the same. There is a very small
difference in the flattening which results in the semi-minor axis 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.
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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
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 files need to be included in the same subdirectory as the AERMAP input
file or the directory where they are located specified using the NADGRIDS keyword described
in Section 3.2.8.
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 NADCON grid shift files
Beginning with version 09040, the user has the option of specifying the pathname for the
folder that contains the NADCON grid shift files (*.las and *.los files) needed for AERMAP
applications involving NAD shift calculations. The pathname may be defined using the full path
or using a relative path reference. As noted in Section 3.2.7, the NADCON grid shift files are
only required when a NAD conversion is needed based on the user specified NADA and the
reference datums among the input terrain files. The default location (path) for these grid shift
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files is the local folder where the AERMAP input file (aermap.inp) is located. This may require
multiple copies of the grid shift files to be located in different folder locations on a computer.
The optional NADGRIDS keyword on the CO pathway allows for the user to specify a single
pathname for the folder containing the grid shift files that can be shared across multiple
applications of AERMAP. The syntax and type of the NADGRIDS keyword are summarized
below:
Syntax:
CO NADGRIDS NADGridPathname
Type:
Optional, Non-repeatable
where the NADGridPathname parameter is a character field that identifies the pathname for the
folder that contains the NADCON grid shift files. The NADGridPathname field can be up to 200
characters in length based on the default parameters in AERMAP. Double quotes (") at the
beginning and end of the pathname can also be used as field delimiters to allow pathnames with
embedded spaces, and do not count toward the 200 character limit. Note that the optional NAD
grid pathname must include the trailing backslash (\) for Windows applications or forward
slash(/) for Linux/UNIX applications. AERMAP also preserves the case for the pathname
specified to accommodate case-sensitivity of filenames for Linux/UNIX applications.
3.2.9 Debug output files
Beginning with version 06341, the AERMAP program includes both mandatory and
optional (user-specified) debug output files. The three mandatory debug files provide general
information regarding the DEM or NED files and domain setup that may be useful in
documenting and resolving problems with the AERMAP code or with the setup of the input data.
The filenames for these mandatory debug output files are hardcoded as MAPDETAIL.OUT,
MAPPARAMS.OUT, and DOMDETAIL.OUT. Beginning with version 18081, when using the
command line option to specifiy the input runstream input file and optionally, the output
filename, AERMAP will use the output file's prefix as the filename of these files. If the output
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filename contains a full or relative pathname, that will be included in those filenames as well, i.e.
these files will be in the same folder as the AERMAP output file.
The MAPDETAIL.OUT file contains a summary of information regarding each DEM or
NED file based on the results of the DEMCHK or NEDCHK routines. In the case of NED data,
the MAPDETAIL.OUT file will contain additional details related to any error or warning
messages generated in the processing the TiffTags or GeoKeys. The MAPPARAMS.OUT file
contains a summary of the parameters for each DEM or NED file, based on the contents of the
header record (logical record type A) for DEM or the TiffTags and GeoKeys for NED data, and
also documents the adjacency of the DEM or NED files within the application area.
The DOMDETAIL.OUT file contains information regarding the extent of the user-
specified modeling domain, including which DEM or NED file contains each corner of the
domain. The DOMDETAIL.OUT file also includes information regarding the direct access
elevation files created for each DEM or NED file, which include only that portion of the file that
is within the domain. This information can be helpful in resolving issues with the domain
exceeding the extent of the DEM or NED files. Beginning with version 09040, a simple option to
avoid problems with the domain exceeding the range of the data is to omit the DOMAINLL or
DOMAINXY keyword. The DOMDETAIL.OUT file is not generated if a domain is not
specified.
The MAPP ARAMS.OUT file includes three separate adjacency tests with different
distance tolerances for adjacency and with somewhat different purposes. The most stringent
adjacency test uses a distance tolerance of 0.1 arc-second (about 3 meters), and is intended to
identify possible "stray" files within the domain or files which have non-standard corner
coordinates. A file must have two corners that meet this test to be considered adjacent to another
file. For DEM data this adjacency test may flag files that were converted to DEM data from
another data format or from DEM files with different resolutions (e.g., from 1-degree DEM to
7.5-minute DEM format). Failing this stringent adjacency test does not necessarily indicate a
problem with the data, but may highlight potential issues for resolution. This stringent test is less
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meaningful for AERMAP applications with multiple NED files, since these files will typically not
follow a regular grid pattern for file extents.
A second, less stringent test for adjacency in the MAPPARAMS.OUT file based on a
tolerance of 45 arc-seconds (about 10 percent of the range of a 7.5-minute DEM file) is used to
develop a 3x3 array of adjacent (neighboring) files for each data file to document relative
locations within the application domain. For applications involving DEM or NED files with
different horizontal resolutions, neighboring files with the same resolution as the reference file
(center of the 3x3 grid) will be given preference over other files that may also meet the criterion.
The third adjacency test included in the MAPP ARAMS.OUT file uses a tolerance of 0.03
degrees (about 3 kilometers) to create a grid showing the relative locations of all data files and
potential data gaps covering the full application domain. For AERMAP applications that utilize
files of the same resolution, interpretation of the full grid of files is straightforward. For
applications involving files with mixed resolution, the "grid" resolution (area covered by each
filename) is based on the horizontal coverage of the highest resolution data file included in the
application. Higher resolution data are given preference over lower resolution data in the grid
printout, and lower resolution files may not be printed as a result. The area covered by lower
resolution data files may include more than one "grid cell", and these filenames are positioned
within the grid based on the southeast corner coordinates.
Optional debug output files are specified with the DEBUGOPT keyword that was added
to the CO pathway beginning with version 06341. The specification of these files is optional.
Separate debug files are available to document calculations related to the determination of the
critical hill height scales, receptor elevations and coordinate conversions, and source elevations
and coordinate conversions. Each debug output file has a default filename defined within the
AERMAP program, but separate keywords on the OU pathway (see Section 3.5) may be used to
specify alternative filenames for these files.
The syntax and type of the DEBUGOPT keyword are:
3-21
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Syntax: CO DEBUGOPT HILL and/or RECEPTOR and/or SOURCE
or
CO DEBUGOPT ALL
Type: Optional, Non-repeatable
where the HILL, RECEPTOR and SOURCE keywords can be used to request specific types of
debug outputs, while the ALL keyword can be used to request all three types of debug outputs.
The keywords are not case-sensitive, and the order of keywords for the first option is not critical.
Also note that SOURCE debug outputs will only be generated if source locations are included in
the AERMAP input file.
The HILL debug option includes a single debug file that documents the calculations of the
critical hill height scales. The default filename for the HILL debug output is
'CALCHCDET.OUT'. For each receptor, the HILL debug output file summarizes the search for
critical hill heights for each DEM or NED file within the domain. In order to minimize the size
of the HILL debug output file, only terrain nodes that factor into the critical hill height calculation
are documented. A sample from a HILL debug output file is provided below in Figure 2-2.
The RECEPTOR and SOURCE debug options each produce three files with the same type
of information for receptors or sources, respectively. The discussion here will focus on receptors
but also applies to sources. The first file provides details regarding the NAD conversion results
and domain checks (if a domain is specified) for each receptor, with a default filename of
'RECDETAIL.OUT'. The second file provides results of calculations to locate which DEM or
NED file contains each receptor, with a default filename of 'RECNDEM.OUT'. The third file
contains results of the receptor elevation calculations, with a default filename of
'RECELV.OUT'. Samples from each of these types of RECEPTOR debug files are provided in
Figures 2-3 through 2-5.
3.2.10 To run or not to run - that is the question
3-22
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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:
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
3-23
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is used to specify the origin for a polar grid. Since allocatable arrays are used in AERMAP, the
number of sources is limited only by the physical memory of the computer AERMAP is running
on.
3.3.1 Including source data from an external file
Beginning with version 09040, the user has the option of including source data from an
external file by using the INCLUDED keyword on the source (SO) pathway. An INCLUDED
keyword may be placed anywhere within the SO pathway, after the STARTING card and before
the FINISHED card (i.e., the SO STARTING and SO FINISHED keywords cannot be included
in the external file). The data in the included file will be processed as though it were part of the
runstream file. The syntax and type of the INCLUDED keyword are summarized below:
Syntax: SO INCLUDED SrcIncFile
Type: Optional, Repeatable
where the Srclncfil parameter is a character field that identifies the filename for the included
source file. The INCLUDED filenames can be up to 200 characters in length based on the default
parameters in AERMAP. Double quotes (") at the beginning and end of the filename can also be
used as field delimiters to allow filenames with embedded spaces. The contents of the included
file must be valid runstream images for the appropriate pathway. If an error is generated during
processing of the included file, the error message will report the line number of the included file.
If more than one INCLUDED file is specified for a particular pathway, the user will first need to
determine which file the error occurred in. If the starting column of the main runstream input file
is shifted from column 1, then the runstream images in the included file must be offset by the
same amount.
3-24
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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
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 Including receptor data from an external file
Beginning with version 09040, the user has the option of including source data from an
external file by using the INCLUDED keyword on the receptor (RE) pathway. An INCLUDED
keyword may be placed anywhere within the RE pathway, after the STARTING card and before
the FINISHED card (i.e., the RE STARTING and RE FINISHED keywords cannot be included in
the external file). The data in the included file will be processed as though it were part of the
runstream file. The syntax and type of the INCLUDED keyword are summarized below:
Syntax: RE INCLUDED RecSrcIncFile
Type: Optional, Repeatable
3-25
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where the Srclncfil parameter is a character field that identifies the filename for the included
source file. The INCLUDED filenames can be up to 200 characters in length based on the default
parameters in AERMAP. Double quotes (") at the beginning and end of the filename can also be
used as field delimiters to allow filenames with embedded spaces. The contents of the included
file must be valid runstream images for the appropriate pathway. If an error is generated during
processing of the included file, the error message will report the line number of the included file.
If more than one INCLUDED file is specified for a particular pathway, the user will first need to
determine which file the error occurred in. If the starting column of the main runstream input file
is shifted from column 1, then the runstream images in the included file must be offset by the
same amount.
3.4.2 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 "subpathways," since
their secondary keywords include a STArt and an END card to define the start and end of inputs
for a particular network.
3,4,2,1 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 "subpathway," in that there are 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 GRIDCART keyword are summarized below:
3-26
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3-27
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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
. Zelevn
FLAG
Row
Zflagl
Zflag2 .
. Zflagn
END
Type:
Optional, Repeatable
where the parameters are defined as follows:
3-28
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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
Xinit
Starting x-axis grid location in meters
Xnum
Number of x-axis receptors
Xdelta
Spacing in meters between x-axis receptors
Yinit
Starting y-axis grid location in meters
Ynum
Number of y-axis receptors
Ydelta
Spacing in meters between y-axis receptors
XPNTS
Keyword identifying grid network defined by a series of discrete x and y
coordinates fused with YPNTS)
Gridxl
Value of first x-coordinate for Cartesian grid (m)
Gridxn
Value of 'nth' x-coordinate for Cartesian grid (m)
YPNTS
Gridyl
Keyword identifying grid network defined by a series of discrete x and y
coordinates (used with XPNTS)
Value of first y-coordinate for Cartesian grid (m)
Gridyn
Value of'nth' y-coordinate for Cartesian grid (m)
ELEV
Keyword to specify that receptor elevations follow (optional)
Row
Indicates which row (v-coordinate fixed) is being incut (Row=l means first
i.e., southmost row)
Zelev
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 eauals the number of x-coordinates for that
network
FLAG
Keyword to specify that flagpole receptor heights follow (optional)
Row
Indicates which row (y-coordinate fixed) is being input (Row=l means first,
i.e., southmost row)
Zflag
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
END
Indicates the END of GRIDCART inputs for a particular network, repeated for
each new Netid
3-29
-------
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 8-by-4 Cartesian grid
network:
3-30
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RE
GRIDCART
CAR1
STA
RE
GRIDCART
CAR1
XPNTS
-500.
-400.
. -20C
i.
-100.
100.
200.
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.
20.
20
. 20.
20.
20.
20
RE
GRIDCART
CAR1
ELEV
3
30.
30.
30.
30
. 30.
30.
30.
30
RE
GRIDCART
CAR1
ELEV
4
40.
40.
40.
40
. 40.
40.
40.
40
RE
GRIDCART
CAR1
FLAG
1
10.
10.
10.
10
. 10.
10.
10.
10
RE
GRIDCART
CAR1
FLAG
2
20.
20.
20.
20
. 20.
20.
20.
20
RE
GRIDCART
CAR1
FLAG
3
30.
30.
30.
30
. 30.
30.
30.
30
RE
GRIDCART
CAR1
FLAG
4
40.
40.
40.
40
. 40.
40.
40.
40
RE
GRIDCART
CAR1
END
RE GRIDCART CAR1 STA
XPNTS -500.-400. -200. -100 100. 200. 400. 500
YPNTS
¦500.
ELEV
1
CO
*
O
FLAG
1
CO
*
O
ELEV
2
CO
*
ro
o
FLAG
2
CO
*
ro
o
ELEV
3
CO
*
CO
o
FLAG
3
CO
*
CO
o
ELEV
4
CO
*
o
FLAG
4
CO
*
o
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, i.e., -500., -250., 250., 500. 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
YPNTS
ELEV
FLAG
ELEV
FLAG
ELEV
FLAG
ELEV
FLAG
RE GRIDCART CAR1 END
500.-400. -200. -100. 100. 200. 400. 500.
500.-250. 250. 500.
500. 8*10.
500. 8*10.
250. 8*20.
250. 8*20.
250. 8*30.
250. 8*30.
500. 8*40.
500. 8*40.
3-31
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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
3.4.2.2 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
or
or
PRIG Xinit Yinit
ORIG Srcid
DIST Ringl Ring2 Ring3 ... Ringn
DDIR Dirl Dir2 Dir3 ... Dim
GDIR Dirnum Dirini Dirinc
ELEV Dir Zelevl Zelev2 ... Zelevn
FLAG Dir Zflagl Zflag2 ... Zflagn
END
Type: Optional, Repeatable
3-32
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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
Dim
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
Zflag
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,y coordinates. The ELEV and FLAG keywords
3-33
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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
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:
3-34
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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.
3.4.3 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 ORIG 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.
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
3-35
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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.
3.4.4 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).
3.4.5 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
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.
3-36
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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.
3,4,5,1 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
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
3-37
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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.
3,4.5,2 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
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.
3-38
-------
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 Srcfil
Type: Mandatory, Non-repeatable
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.
The options for user-specified filenames are provided with the DEBUGHIL,
DEBUGREC, and DEBUGSRC keywords on the OU pathway. The syntax and type of the
DEBUGHIL keyword are:
Syntax: OU DEBUGHIL HillDebug
Type: Optional, Non-repeatable
where the HillDebug parameter is the user-specified name for the HILL debug file. The syntax
and type of the DEBUGREC and DEBUGSRC keywords are:
3-39
-------
Syntax:
OU DEBUGREC RecDetail
RecNDem
RecElv
OU DEBUGSRC SrcDetail
SrcNDem
SrcElv
Type:
Optional, Non-repeatable
where the RecDetail, RecNDem, and RecElv parameters are the debug filenames for the NAD
conversion and domain check file, the DEM/NED assignment file, and the receptor elevation file,
respectively. The source debug files and naming convention follow the same pattern as the
receptor debug files. All debug filenames can be up to 200 characters in length, up to a
maximum record length of 512 characters, based on the default parameters in AERMAP. Double
quotes (") at the beginning and end of the filename can also be used as field delimiters to allow
filenames with embedded spaces. Figure 3-1 shows a sample of the HILL debug output file and
Figure 3-2 through Figure 3-4 show samples of the RECEPTOR output debug files.
3-40
-------
** AERMAP - VERSION 11103
08/25/16
**
15:19
: 43
Entering CALCHC
for Receptor:
1
Starting with Local DEM
File:
1
Checking DEM File 1
: NWDurham 10m.dem
for Receptor No.:
1
DEM
RECLAT
RECLON DEM SELAT
DEM SELON
DIST(m)
MAXELEV
RECELEV
36.058
-78.946
36.000
-78.875
0 .00
227.40
120.34
REC NADA DEM
NADD
Map
Name
Latitude Longitude
Northing
Easti
ng
Zone
111
1 NORTHWEST
DURHAM,
NC-
240 129807
.66 -284205
.06
3992098.48
685017.
36
17
DEM
PROF
NODE
NODE
-Y
NODE-X
DIST
ZNODE
RE LEV
HEFMAX
1
135
169
3992180
00
684840.00
195.20
140.00
120.34
140.00
1
135
170
3992190
00
684840.00
199.58
140.30
120.34
140.30
1
136
169
3992180
00
684850.00
186.16
140.60
120.34
140.60
1
136
170
3992190
00
684850.00
190.75
140.80
120.34
140.80
1
136
171
3992200
00
684850.00
195.75
141.00
120.34
141.00
The Critical Hill
Height
for Receptor:
1
is 141.00
meters.
Checking DEM Fil
e 1
: NWDurham 10m.dem
for Receptor No.:
2
DEM
RECLAT
RECLON DEM SELAT
DEM SELON
DIST(m)
MAXELEV
RECELEV
36.059
-78.946
36.000
-78.875
0 .00
227.40
123.76
REC NADA DEM
NADD
Map
Name
Latitude Longitude
Northing
Easti
ng
Zone
2 11
1 NORTHWEST
DURHAM,
NC-
240 129810
.85 -284204
.29
3992196.96
685034.
73
17
DEM
PROF
NODE
NODE
-Y
NODE-X
DIST
ZNODE
RE LEV
HEFMAX
1
161
171
3992200
00
685100.00
65.34
130.30
123.76
130.30
The Critical Hill
Height
for Receptor:
2
is 130.30
meters.
Checking DEM File 1
: NWDurham 10m.dem
for Receptor No.:
3
DEM
RECLAT
RECLON DEM SELAT
DEM SELON
DIST(m)
MAXELEV
RECELEV
36.059
-78.945
36.000
-78.875
0 .00
227.40
128.51
REC NADA DEM
NADD
Map
Name
Latitude Longitude
Northing
Easti
ng
Zone
3 11
1 NORTHWEST
DURHAM,
NC-
240 129814
.03 -284203
. 51
3992295.44
685052.
09
17
DEM
PROF
NODE
NODE
-Y
NODE-X
DIST
ZNODE
RE LEV
HEFMAX
1
157
181
3992300
00
685060.00
9. 13
129.60
128.51
129.60
1
158
180
3992290
00
685070.00
18.71
130.50
128.51
130.50
1
158
181
3992300
00
685070.00
18.48
130.60
128.51
130.60
1
158
186
3992350
00
685070.00
57 .42
134.30
128.51
134.30
1
158
187
3992360
00
685070.00
6 6.99
135.60
128.51
135.60
1
158
188
3992370
00
685070.00
76. 68
136.80
128.51
136.80
1
158
189
3992380
00
685070.00
86.43
137.60
128.51
137.60
1
159
189
3992380
00
685080.00
89.04
138.30
128.51
138.30
1
159
190
3992390
00
685080.00
98 .59
138.80
128.51
138.80
1
160
189
3992380
00
685090.00
92 . 67
139.00
128.51
139.00
1
160
190
3992390
00
685090.00
101.87
139.60
128.51
139.60
1
160
191
3992400
00
685090.00
111.22
140.10
128.51
140.10
1
161
191
3992400
00
685100.00
115.01
140.60
128.51
140.60
1
162
191
3992400
00
685110.00
119.52
140.80
128.51
140.80
1
163
191
3992400
00
685120.00
124.67
141.10
128.51
141.10
The Critical Hill
Height
for Receptor:
3
is 141.10
meters.
Figure 3-1. Sample from HILL Debug Output File
3-41
-------
** AERMAP - VERSION 11103
08/25/16
15:19:43
Processing Receptor Location
Data
m RECCNV:
Determining North American
Datum
(NAD) shift
values in arc-seconds.
Total shift (meters) includes both datum
shift and projection shift
for Lat/Lon to UTM
coordinates.
No NAD conversions
requirec
. All
files are consistent with NADA =
1
Checking Receptor Locations Relative to the
Domain in CHKEXT;
Domain and Receptor Coordinates
m UTM Meters
REC
ZONE
UTM-Y
(m)
UTM-X
(m)
DOM
ZONE/NORTH/EAST#
17
3993500
000
686500
000
REC
ZONE/NORTH/EAST#
1
17
3992098
481
685017
365
DOM
ZONE/NORTH/EAST#
17
3990500
000
683500
000
DOM
ZONE/NORTH/EAST#
17
3993500
000
686500
000
REC
ZONE/NORTH/EAST#
2
17
3992196
962
685034
730
DOM
ZONE/NORTH/EAST#
17
3990500
000
683500
000
DOM
ZONE/NORTH/EAST#
17
3993500
000
686500
000
REC
ZONE/NORTH/EAST#
3
17
3992295
442
685052
094
DOM
ZONE/NORTH/EAST#
17
3990500
000
683500
000
DOM
ZONE/NORTH/EAST#
17
3993500
000
686500
000
REC
ZONE/NORTH/EAST#
4
17
3992492
404
685086
824
DOM
ZONE/NORTH/EAST#
17
3990500
000
683500
000
DOM
ZONE/NORTH/EAST#
17
3993500
000
686500
000
REC
ZONE/NORTH/EAST#
5
17
3992984
808
685173
648
DOM
ZONE/NORTH/EAST#
17
3990500
000
683500
000
DOM
ZONE/NORTH/EAST#
17
3993500
000
686500
000
REC
ZONE/NORTH/EAST#
6
17
3992093
9 6 9
685034
202
DOM
ZONE/NORTH/EAST#
17
3990500
000
683500
000
DOM
ZONE/NORTH/EAST#
17
3993500
000
686500
000
REC
ZONE/NORTH/EAST#
7
17
3992187
939
685068
404
DOM
ZONE/NORTH/EAST#
17
3990500
000
683500
000
DOM
ZONE/NORTH/EAST#
17
3993500
000
686500
000
REC
ZONE/NORTH/EAST#
8
17
3992281
908
685102
606
DOM
ZONE/NORTH/EAST#
17
3990500
000
683500
000
DOM
ZONE/NORTH/EAST#
17
3993500
000
686500
000
REC
ZONE/NORTH/EAST#
9
17
3992469
846
685171
010
DOM
ZONE/NORTH/EAST#
17
3990500
000
683500
000
DOM
ZONE/NORTH/EAST#
17
3993500
000
686500
000
REC
ZONE/NORTH/EAST#
10
17
3992939
693
685342
020
DOM
ZONE/NORTH/EAST#
17
3990500
000
683500
000
Figure 3-2. Sample from the RecDetail Debug File for NAD Conversions and Domain Check
3-42
-------
AERMAP - VERSION 11103
08/25/16
15:19:43
LOOKING AT DEMs FOR REC:
REC#: 1 RLAT/LON
SHIFTL/L(S)
UTM (E/N/ Zon)
SHIFTX/Y(M)
36.05768403
0.00000000
685017.365
0.00000000
-78.94585057
0 .00000000
3992098.481
0.00000000
17
REC NAD: 1
DEM No.:
1 DEM Name: NORTHWEST DURHAM, NC-24 000
DEM Max. LAT/LON(D.D)
Rec LAT/LON(D.D)
DEM Min. LAT/LON(D.D)
36.12500
36.05768
36.00000
-78 . 87500
-78 . 94585
-7 9.00000
DEM NAD: 1
DEM Max. LAT/LON(Sec)
Rec LAT/LON(Sec)
DEM Min. LAT/LON(Sec)
130050.00000
129807.66252
129600.00000
-283950.00000
-284205.06207
-284400.00000
DEM No.
1 Contains Rec No.:
1
LOOKING AT DEMs FOR REC:
REC#: 2 RLAT/LON
SHIFTL/L(S)
UTM (E/N/ Zon)
SHIFTX/Y(M)
36.05856807
0.00000000
685034.730
0.00000000
-78 . 94563482
0.00000000
3992196.962
0.00000000
17
REC NAD: 1
DEM No.:
1 DEM Name: NORTHWEST DURHAM, NC-24 000
DEM Max. LAT/LON(D.D)
Rec LAT/LON(D.D)
DEM Min. LAT/LON(D.D)
36.12500
36.05857
36.00000
-78 . 87500
-78 . 94563
-7 9.00000
DEM NAD: 1
DEM Max. LAT/LON(Sec)
Rec LAT/LON(Sec)
DEM Min. LAT/LON(Sec)
130050.00000
129810.84505
129600.00000
-283950.00000
-284204.28536
-284400.00000
DEM No.
1 Contains Rec No.
2
LOOKING AT DEMs FOR REC:
REC#: 3 RLAT/LON
SHIFTL/L(S)
UTM (E/N/ Zon)
SHIFTX/Y(M)
36.05945210
0.00000000
685052.094
0.00000000
-78 . 94541906
0.00000000
3992295.442
0.00000000
17
REC NAD: 1
DEM No.
1 DEM Name: NORTHWEST DURHAM, NC-24 000
DEM Max. LAT/LON(D.D)
Rec LAT/LON(D.D)
DEM Min. LAT/LON(D.D)
36.12500
36.05945
36.00000
-78 . 87500
-78 . 94542
-7 9.00000
DEM NAD:
DEM Max. LAT/LON(Sec)
Rec LAT/LON(Sec)
DEM Min. LAT/LON(Sec)
130050.00000
129814.02757
129600.00000
-283950.00000
-284203.50863
-284400.00000
DEM No.
1 Contains Rec No.
3
LOOKING AT
REC#:
DEMs FOR REC:
4 RLAT/LON
SHIFTL/L(S)
UTM (E/N/ Zon)
SHIFTX/Y(M)
36.06122017
0.00000000
685086.824
0.00000000
-78.94498753
0 .00000000
3992492.404
0.00000000
17
REC NAD: 1
Figure 3-3. Sample from the RecNDem Debug File for Assigning Local DEM/NED File
3-43
-------
AERMAP - VERSION 11103
08/25/16
15:19:43
From RECELV:
Recept
or ¦
I ERR =
0
I ERR =
-1
I ERR =
-2
I ERR =
-3
180 receptors
normal (non-edge) case
edge receptor, no y-adjustment
edge receptor, w/ y-adjustment
receptor beyond range of data;
possible gap within data file;
flagged with warning message 400
RECEPTOR ELEVATION CALCS FOR REC#
LOCATED IN DEM FILE:
1 ; NWDurham 10m.dem
DEM FILE NAD:
1 ; ANCHOR POINT NAD:
DEM FILE ZONE: 17
RECEPTOR LOCATION (Lon, Lat, arc-seconds)
(Lon, Lat, dec-degrees)
(UTMx, UTMy, Zone)
CALLING FIND4 w/ IREC, JDEM:
FIND4:
DEM REC
1 1
XRR
685017.3648
YRR
3992098.4808
-284205.0621
-78 . 945851
685017.36
129807.6625
36 .057684
3992098.48 17
NORTHWEST DURHAM, NC-24000
SW
Corner
NW Corner
NE Corner
SE Corner
Easting:
680270.939
679985.884
691236.541
691539
. 436
Northing:
3985597.778 3999464.516
3999703.384
3985836
. 309
Latitude:
36.0000
36 .1250
36 .1250
36 .
0000
Longitude:
-
79.0000
-79.0000
-78.8750
-78 .
8750
Based on the
Find4
Coding of:
IP= 4 3
1 1
IP= 1 2
IP xbase
nx
XX
X-Receptor
ybase
ny
YY
Y-Receptor
1 683500.00
152
685010.00
685017.36
3990500.00
160
3992090.00
3992098.48
2 683500.00
153
685020.00
685017.36
3990500.00
160
3992090.00
3992098.48
3 683500.00
153
685020.00
685017.36
3990500.00
161
3992100.00
3992098.48
4 683500.00
152
685010.00
685017.36
3990500.00
161
3992100.00
3992098.48
DEM RECNUM:
IERR = 0
IP JREC
NX
NY
1 45611
152
160
2 45912
153
160
3 45913
153
161
4 45612
152
161
Based on the DEM Coding of:
IP= 2 3
I I
IP= 1 4
RECELV:
X-Rec
Y-Rec
685017.36
3992098 .48
IP
JREC
DEM
XDM
YDM
ELEV
1
45611
1
685010.00
3992090.00
119.00
2
45612
1
685010.00
3992100.00
119.30
3
45913
1
685020.00
3992100.00
120.80
4
45912
1
685020.00
3992090.00
120.30
ELEVATION (M)
FOR IREC
1 =
120.34
Figure 3-4. Sample from the RecElv Debug File for Receptor Elevation Calculations
3-44
-------
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 2-2). 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.
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.
4-1
-------
4.2 Digital elevation model (DEM) data
The USGS distributes DEM data in several scales from the 1-degree series at a scale
ofl :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 (e.g., 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
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.
• 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) as a result 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.
4-2
-------
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.
Ax = 30 meters (Easting)
Ay = 30 motsrs (Northing)
O = Elevation point in adjacent
quadrangle
• = Elevation point
% = First point along profile
= Corner of DEM polygon
17.5-minute quadrangle cornersl
(Example is a quadrangle west of
central meridian of UTM zone,)
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, shown in Table 4-1, 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 circles outside the border of the quadrangle.
4-3
Easting
-------
The non-filled circles represent nodes located in 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.
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.
4-4
-------
A* i 3 art Hearts
Ac -3 arc stconds
• ¦ EltvKKjn DOin1
t * Fifjl paint akJrtg profile
n » Corner of DEM polygon
(I" bloc*!1
Longitude
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 Table 4-1 and Table 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.
4-5
-------
Table 4-1. DEM Data Elements - Logical Record Type A
Physical Record Format
Data
Element
Description
Type
(Fortran Notation)
ASCII
Format
Starting
Byte
Ending
Byte
Comment
1
File name
ALPHA
A40
1
40
DEM quadrangle name.
Free Format Text
ALPHA
A40
41
80
Free format descriptor field, contains useful information related to digital
process such as digitizing instrument, photo codes, slot widths, etc.
Filler
—
—
81
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
3
DEM level code
INTEGER*2
16
145
150
Code 1=DEM-1 =DEM-2 3=DEM-3
4
Code defining
INTEGER*2
16
151
156
Code l=regular
elevation pattern
2=random is reserved for future use
(regular or random)
5
Code defining ground
planimetric reference system
INTEGER*2
16
157
162
Code 0=Geographic
1=UTM
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.
6
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.
7
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.
8
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
9
Code defining unit of measure for
elevation coordinates throughout
the file
INTEGER*2
16
535
540
Code l=feet for elevation coordinates, 2=meters
Normally code 2, meters, for 7.5-minute and 1-degree DEM's
4-6
-------
Physical Record Format
Data
Element
Description
Type
(Fortran Notation)
ASCII
Format
Starting
Byte
Ending
Byte
Comment
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 containing the
ground coordinates of the four
corners for
the DEM
REAL* 8
4(2D24.1
5)
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.
14
Accuracy code for elevations
INTEGER*2
16
811
816
Code 0=unknown accuracy elevations
l=accuracy information is given in logical record type C (not used)
15
A three element array of DEM
spatial resolution for x, y, z.
Units of measure are consistent
with those indicated by data
elements 8 and 9 in this record
REAL*4
3E12.6
817
852
These elements are usually set to;
30, 30, 1 for 7.5-minute DEM's,
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
16
A two-element array containing
the number of rows and columns
(m,n) of profiles in the DEM
INTEGER*2
216
853
864
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
Note: Old format stops here
17
Largest primary contour interval
INTEGER*2
15
865
869
Present only if two or more contour interval primary intervals exist.
18
Source contour
INTEGER* 1
11
870
Corresponds to the units of the map interval 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 units
INTEGER* 1
11
876
Corresponds to the units of the map interval smallest primary contour
interval: l=feet, 2=meters
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/ revision date
INTEGER*2
14
881
884
YYMM two-digit year and two-digit month
23
Inspection/revision flag
ALPHA* 1
A1
885
"I" Qr H£U
23
4-7
-------
Physical Record Format
Data
Element
Description
Type
(Fortran Notation)
ASCII
Format
Starting
Byte
Ending
Byte
Comment
24
Data validation flag
INTEGER* 1
11
886
0= No validation performed.
1=TESDEM (record C added) no qualitative 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.
25
Suspect and void area flag
INTEGER* 1
12
887
888
0=none
l=suspect areas
2=void areas
3=suspect and void areas
26
Vertical datum
INTEGER* 1
12
889
890
l=local mean sea level
2=National Geodetic Vertical Datum 1929 (NGVD 29)
3=North American Vertical Datum 1988 (NAVD 88)
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).
4-8
-------
Table 4-2. DEM Data Elements - Logical Record Type B (Data Record)
Physical Record Format
Data
Element
Description
Type
(Fortran Notation)
ASCII
Format
Starting
Byte
Ending
Byte
Comment
1
A two-element array containing
the row and column
identification number of the
DEM profile contained in this
record
INTEGER*2
216
1
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.
2
A two-element array containing
the number (m,n) of elevations
in the DEM profile
INTEGER*2
216
13
24
The first element in the field corresponds to the number of rows and
columns of nodes in this profile. The second element is set to 1, specifying
one column per B record
3
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.
4
Elevation of local datum for
profile
REAL* 8
D24.15
73
96
The values are in the units of measure given by data element 9, logical
record type A
5
A two-element array of
minimum and maximum
elevations for the profile
REAL* 8
2D24.15
97
144
The values are in the unit of measure given by data element 9, logical
record type A
6
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 = ma for
subsequent blocks
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
4-9
-------
4.3 Data manipulation of DEM files 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 TDX'. 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 systems 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 2-4). 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 nearby elevation nodes.
4-10
-------
4.4 Determining receptor (source) elevations using DEM data
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:
Weighing Factor (w) = 1/distl + l/dist2 + l/dist3 + l/dist4
Elevation = elevl/(distl*w) + elev2/(dist2*w) + elev3/(dist3*w) + elev4/(dist4*w).
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
4-11
-------
closest to the receptor or source location and may include elevations from two or more DEM
files.
4-12
-------
5.0 References
Aldus, 1992: TIFF, Revision 6.0. Aldus Corporation, Seattle, WA.
www.alternatiff.com/resources/TIFF6.pdf
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, 2018a: User's Guide for the AMS/EPA Regulatory Model -
AERMOD. - EPA-454/B-18-001. U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina 27711.
Environmental Protection Agency, 2018b: User=s Guide for the AERMOD Terrain Preprocessor
(AERMAP). EPA-454/B-18-004. 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 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)
Federal Communications Commission, 1984: Use of Computer-Generated Terrain Data for
Determining Antenna Height Above Average Terrain, Interim Procedure Per General
Docket 84-705. Federal Communications Commission, Washington, DC 20554.
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)
Ritter, N. and M. Ruth, 1995: GeoTIFF Format Specification.
www.remotesensing.org/geotiff/spec/geotiffhome.html
Snyder, J., 1987: Map Projections - A Working Manual, U.S. Geological Survey Professional
Paper 1395. U.S. Government Printing Office, Washington, D.C.
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, 1998: Standards for Digital Elevation Models, National Mapping
Program Technical Instructions, http://rockyweb.cr.usgs.gov/nmpstds/demstds.html
5-1
-------
U.S. Department of the Interior, Reston, Virginia 20192.
U.S. Geological Survey, 2002: The National Map - Elevation, Fact Sheet 106-02 (November
2002). http://egsc.usgs.gov/isb/pubs/factsheets/fsl0602.html U.S. Department of the
Interior, Reston, Virginia 20192.
U.S. National Geodetic Survey, NADCON - North American Datum Conversion Utility,
http://www.ngs.noaa. gov:8Q/TOOLS/Nadcon/Nadcon. html
5-2
-------
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
-------
Table A-l. All Keywords Available in AERMAP
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
DEBUGHIL
OU
O-N
Specifies filename for the optional hill height debug output file
DEBUGOPT
CO
O-N
Specifies whether additional debug output files will be
generated for receptors, sources, and/or hill heights
DEBUGREC
OU
O-N
Specifies filenames for optional receptor debug output files
DEBUGSRC
OU
O-N
Specifies filenames for optional source debug output files
DISCCART
RE
0 - R
Defines discrete receptor locations referenced to a Cartesian
system
DISCPOLR
RE
0 - R
Defines discrete 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
INCLUDED
SO,
RE
0 - R
Allows sources and/or receptors from external files to be
included in the inputs
LOCATION
SO
0 - R
Specifies the location of sources
NADGRIDS
CO
O-N
Specifies optional pathname for the location ofNADCON grid
shift files
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
A-2
-------
Keyword
Path
Type
Keyword Description
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-3
-------
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
O-N
Optional second line of title for output
TERRHGTS
O-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
O-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
0 1 -N
Allows the user to specify the domain extent in the latitude/longitude
coordinate system
DOMAINXY
0 1 -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
DEBUGOPT
O-N
Specifies whether the optional debug output files for sources, receptors,
and/or hill heights will be generated
NADGRIDS
O-N
Specifies optional pathname for location of NADCON grid shift files
(*.las and *.los)
RUNORNOT
M-N
Identifies whether to run program or process setup information
onlv
FINISHED
M-N
Identifies the end of CONTROL pathway inputs
Type: M - Mandatory N - Non-Repeatable
O - Optional R - Repeatable
1) DOMAINLL and DOMAINXY are optional but only one can be used in an AERMAP. run
B-2
-------
Table B-2. Description of Control Pathway Keywords and Parameters
Keyword
Parameters
TITLEONE
Title 1
where:
Title 1
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
DEM (FILLGAPS)
or
NED
where:
DEM
FILLGAPS
NED
Specifies that Digital Elevation Model (DEM) data will be used
(including 7.5-minute, 15-minute, and/or 1-degree DEM data)
Option for AERMAP to calculate elevations for receptors (and/or
sources) located within gap areas based on closest nodes for DEM
data; gap receptor/source elevations will otherwise be assigned a
missing code of -9999.0
Specifies that National Elevation Dataset (NED) data in GeoTIFF
format will be used
DATAFILE
DEM: Demfil (CH
or
NED: Nedfil (TIFI
ECK)
"DEBUG) (ElevUnits)
where:
Demfil
(CHECK)
Nedfil
(TIFFDEBUG)
ElevUnits
Identifies the name of the DEM data file
Option to perform check on the full DEM file
Identifies the name of the NED data file
Option to generate a debug file with all the TiffTags and GeoKeys
included within the NED file (uses hardcoded filename)
Option for user-speified elevation units (accepts FEET. DECIFEET.
DECI-FEET. DECAFEET. DECA-FEET. METERS.
DECIMETERS. DECI-METERS. DECAMETERS, or DECA-
METERS. not case sensitive)
B-3
-------
Keyword
Parameters
DOMAINLL
Lonmin Latmin Lonmax Latmax
where:
Lonmin
Latmin
Lonmax
Latmax
Longitude in decimal dearees for the lower right (SE) corner of the
domain
(negative for West longitude)
Latitude in decimal dearees for the lower riaht (SE) corner of the
domain
Longitude in decimal dearees for the upper left (NW) corner of the
domain
(negative for West longitude)
Latitude in decimal dearees 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
ANCHORXY
Xauser Yauser Xautm Yautm Zautm
where:
Xauser
Yauser
Xautm
Yautm
Zautm
Nada
The X coordinate of any geographic location (typically the origin
0,0) in the user coordinate system in meters
The Y coordinate of any geographic location (typically the origin
0,0) in the user coordinate system in meters
The UTM East coordinate of the same geographic location
specified as Xauser,Yauser in meters
The UTM North coordinate of the same geographic location
specified as Xauser,Yauser in meters
The UTM Zone of the same geographic location corresponding to
Xautm, Yautm
The datum from which the Xautm, Yautm coordinates were
drawn
DEBUGOPT
(HILL) and/or (RECEPTOR) and/or (SOURCE) (Order is not important)
or
ALL
B-4
-------
Keyword
Parameters
where:
RECEPTOR
SOURCE
HILL
ALL
Specifies that receptor debug output files will be generated
Specifies that source debug output files will be generated
Specifies that hill height scale debug output file will be generated
Specifies that ALL types of debug output files will be generated,
including RECEPTOR, SOURCE (if applicable) and HILL
NADGRIDS
NADGridPathname
where:
NADGridPathname
Optional pathname for folder containing the NADCON grid
shift files (*.las and *.los). Without the NADGRIDS keyword,
the default path is the local folder containing the
AERMAP.INP file.
RUNORNOT
RUN or NOT
where:
RUN
NOT
Indicates to run full preprocessor calculations
Indicates to process setup data and report errors, but to not run full
preprocessor calculations
B-5
-------
Table B-3. Description of Source Pathway Keywords
SO Keywords
Type
Keyword Description
STARTING
M-N
Identifies the start of SOURCE pathway inputs
LOCATION
O1 -R
Identifies source locations for use in extracting source elevations
and/or to define the origin of discrete polar receptors
INCLUDED
0 - R
Identifies an external file containing source locations to be included in
the inputs
FINISHED
M-N
Identifies the end of SOURCE pathway inputs
1) The LOCATION keyword is optional if location inputs are specified through the INCLUDED
file option.
Note: AERMAP will ignore the SRCPARAM keyword within the SO pathway. This may facilitate
including portions of an AERMOD input file to determine source elevations, without having to
remove the SRCPARAM records
B-6
-------
Table B-4. Description of Source Pathway Keywords and Parameters
Keyword
Parameters
LOCATION
Srcid Srctyp
Xs Ys (Zs)
where:
Srcid
Alphanumeric source ID, up to eight characters
Srctyp
Source tvoe: POINT. VOLUME. AREA. AREAPOLY. AREACIRC
Xs
x-coordinate (Easting) of source location, corner for AREA, vertex for
AREAPOLY. center for AREACIRC (m)
Ys
y-coordinate (Northing) of source location (m)
Zs
Optional z-coordinate of source location (elevation above mean sea level in
meters)
INCLUDED
SrcIncFile
where
SrcIncFile
Identifies the filename for the included source file, up to 200 characters in
length; double quotes (") may be used as delimiters for the filename to
allow for embedded spaces; and quotes don't count toward the limit of 200
B-7
-------
Table B-5. Description of Receptor Pathway Keywords
RE Keywords
Type
Keyword Description
STARTING
M-N
Identifies the start of RECEPTOR pathway inputs
ELEVUNIT
O-N
Defines input units for receptor elevations (defaults to meters), must be first
keyword after RE STARTING if used.
GRIDCART
O1 -R
Defines a Cartesian grid receptor network
GRIDPOLR
O1 -R
Defines a polar receptor network
DISCCART
O1 -R
Defines the discretely placed receptor locations referenced to a Cartesian system
DISCPOLR
O1 -R
Defines the discretely placed receptor locations referenced to a polar system
EVALCART
O1 -R
Defines discrete Cartesian receptor locations for use with
EVALFILE output option
INCLUDED
0 - R
Identifies an external file containing receptor locations to be included in the inputs
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-8
-------
Table B-6. Description of Receptor Pathway Keywords and Parameters
Keyword
Parameters
ELEVUNIT
METERS or
FEET
where:
METERS
Specifies input units for receptor elevations of meters
FEET
Specifies input units for receptor elevations of feet
Note: This keyword applies to receptor elevations only.
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 Zflaal Zflaa2 Zflaa3 ... ZflaaN
END
where:
Netid
Receptor network identification code (up to eight alphanumeric
characters)
STA
Indicates STArt of GRIDCART subpathway, repeat for each new Netid
XYINC
Keyword identifying grid network generated from x and y increments
Xinit
Starting local x-axis grid location in meters
Xnum
Number of x-axis receptors
Xdelta
Spacing in meters between x-axis receptors
Yinit
Starting local y-axis grid location in meters
Ynum
Number of y-axis receptors
Ydelta
Spacing in meters between y-axis receptors
XPNTS
Keyword identifying grid network defined by a series of x and y coordinates
Gridxl
Value of first x-coordinate for Cartesian grid
GridxN
Value of'nth' x-coordinate for Cartesian grid
YPNTS
Keyword identifying grid network defined by a series of x and y coordinates
Gridyl
Value of first y-coordinate for Cartesian grid
GridyN
Value of'nth' y-coordinate for Cartesian grid
ELEV
Keyword to specify that receptor elevations follow
Row
Indicates which row (y-coordinate fixed) is being input
Zelev
An array of receptor terrain elevations for a particular Row
FLAG
Keyword to specify that flagpole receptor heights follow
Row
Indicates which row (y-coordinate fixed) is being input
Zflag
An array of receptor heights above local terrain elevation for a particular Row
(flagpole receptors)
END
Indicates END of GRIDCART subpathway, repeat for each new Netid
B-9
-------
Table B-6 (cont'd)
Description of Receptor Pathway Keywords and Parameters
GRIDPOLR
Netid STA
ORIG
Xinit Yinit,
or ORIGSrcid
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 ... ZflagN
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 (up to 12 characters)
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
Zflag
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-10
-------
Table B-6 (concluded)
Description of Receptor Pathway Keywords and Parameters
DISCCART
Xcoord Ycoord (Zelev) (Zflag)
where:
Xcoord
Ycoord
Zelev
Zflag
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
Zflag
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 only
for ELEV terrain
Receptor height (flagpole) above local terrain (optional), used only
with FLAGPOLE keyword
EVALCART
Xcoord Ycoord Zelev Zflag Arcid (Name)
where:
Xcoord
Ycoord
Zelev
Zflag
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
only for ELEV terrain
Receptor height (flagpole) above local terrain (optional), used
only with FLAGPOLE keyword
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)
INCLUDED
RecIncFile
Where
RecIncFile
Identifies the filename for the included receptor file, up to 200
characters in length; double quotes (") may be used as delimiters for
the filename to allow for embedded spaces; and quotes don't count
toward the limit of 200
B-ll
-------
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
O-N
Identifies the output filename for source location data
DEBUGHIL
O-N
Identifies the output filename for the optional hill height scale debug file
DEBUGREC
O-N
Identifies the output filename for the receptor debug file
DEBUGSRC
O-N
Identifies the output filename for the optional source debug file
FINISHED
M-N
Identifies the end of OUTPUT pathway inputs
B-12
-------
Table B-8. Description of Output Pathway Keywords and Parameters
Keyword
Parameters
RECEPTOR
Recfil
where:
Recfil
Specifies output filename for receptor elevation and hill height scale data
SOURCLOC
Srcfil
where:
Srcfil
Specifies output filename for source elevation data
DEBUGHIL
HillDebug
where:
HillDebug
Specifies the hill height scale debug file
DEBUGREC
RecDetail
RecNDem RecElv
where:
RecDetail
Specifies the filename for the RecDetail debug file, which provides
information on NAD conversions and domain check
RecNDem
Specifies the filename for the RecNDem debug file, which provides
information on the DEM/NED file assignment
RecElv
Specifies the filename for the RecElv debug file, which provides
information on the receptor elevation calculations
DEBUGSRC
SrcDetail
SrcNDem SrcElv
where:
SrcDetail
Specifies the filename for the SrcDetail debug file, which provides
information on NAD conversions and domain check
SrcNDem
Specifies the filename for the SrcNDem debug file, which provides
information on the DEM/NED file assignment
SrcElv
Specifies the filename for the SrcElv debug file, which provides
information on the source elevation calculations
Note: Receptor elevation, source elevation, and debug output filenames can be up to 200 characters in
length, up to a limit of 512 characters for the full input record; double quotes (") may be used as
delimiters for the filename to allow for embedded spaces; and quotes don't count toward the limit
of200.
B-13
-------
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.2 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 AERMAP Execution ***
Summary of Total Messages
A Total of 0 Fatal Error Message(s)
A Total of 0 Warning Message(s)
A Total of 0 Informational Message(s]
******** FATAL ERROR MESSAGES ********
*** NONE ***
******** WARNING MESSAGES ********
*** NONE ***
~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k
*** AERMAP Finishes Successfully ***
~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k~k
Figure C-l. Example of an AERMAP Message Summary
C.3 Description of the detailed 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):
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.4 Detailed description of the error/message codes
The messages codes and messages that may be issued when AERMAP is run are described in
this section. The codes are divided into five groups: input runstream image structure processing (100-
199), parameter setup processing (200-299), setup data and quality assurance processing (300-399),
runtime message processing (400-499), and input/output message processing (500-599).
C-3
-------
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.
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.
C-4
-------
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.
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,
C-5
-------
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.
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
C-6
-------
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.
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).
C-7
-------
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 than 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.
305 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.
310 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.
320 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.
C-8
-------
330 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.
335 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.
340 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.
350 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.
360 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.
370 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.
375 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.
377 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.
380 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.
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.
C-9
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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 cannot 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
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.
C-10
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United States Office of Air Quality Planning and Standards Publication No. EPA-454/B-18-004
Environmental Protection Air Oualitv Assessment Division April, 2018
Agency Research Triangle Park, NC
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