Detailed Raw Data Download Help

Nearly all of the map layers in the National Atlas Map Maker are also available for download using File Transfer Protocol (ftp). There is no charge for this service. Most of the map layers were compiled at a scale of 1:2,000,000 or a ground resolution of one kilometer. Most map layers cover the full geographic extent of the United States of America, although some cover the conterminous United States.

Generally, map layers are available in Shapefile format and in the Topological Vector Profile of the Spatial Data Transfer Standard (SDTS-TVP). Image files are available in the georeferenced tagged image file format (GeoTIFF). Data tables are distributed in the DBF format. A very few map layers are also offered in Arc/Info Export and Geodatabase formats.

You can use the online, interactive Map Maker to preview the map layers. Though the map layers are compressed for delivery to you, many of these data files are quite large and can take a very long time to download. We no longer offer our data on compact disc.

Frequently Answered Questions for Raw Data Downloads

• How do I learn more about a  particular map layer or data table before downloading?
• Are the map layers compressed?
• How do I get software to  "decompress" them?
• What are the file formats for  the National Atlas map layers and data tables?
• When I decompress a map layer in  Shapefile format, I get four separate files. What are these?
• What kind of software do I need  to do anything with National Atlas map layers?
• Who sells software that  supports map layers in the Shapefile format? In SDTS format? In Export format?
• Some map layers, such as  Butterfly, are listed as "DBF" files. What are these?
• Some map layers, such as Land  Cover Diversity, are listed as "GeoTIFF" files. What are these?
• I am using ESRI's ArcGIS to view a National Atlas raw data file in GeoTIFF format. Do you have a projection file I can use?
• I am using ESRI's ArcGIS to view an Atlas shapefile (.shp). Do you have a projection file I can use?
• Wow! When I decompressed  the Principal Aquifers map layer in SDTS format I got 29 files. What are these?
• Can I order the map layers on  disc or tape?
• How can I understand your file  naming convention?
• What is "metadata?"
• Why is there more than one map  layer for some themes (such as water features)?
• Can I get the 2002 or the 2003 West Nile Virus data?
• How can I learn more about the  National Atlas of the United States?

How do I learn more about a particular map layer before downloading?
You will find links to separate Web pages that describe the contents of each map layer in the first and third columns of the Raw Data Download Table. The first column links to a concise introduction to the map layer. The third column links to its complete raw data documentation file, which complies with the Federal Geographic Data Committee (FGDC) Content Standard for Digital Geospatial Metadata.

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Are the map layers compressed?
Yes. The map layers were compressed on a Unix system using the tar and gzip utilities. We also use the tar utility to combine two or more files into a single file for download. Raw data documentation in text format is also bundled up with each data file.

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How do I get software to "decompress" them?
Here are links to online decompression software for the following operating systems:
- Windows
- Macintosh
- Linux

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What are the file formats for the National Atlas map layers and data tables?

1. Most map layers are available in the Shapefile format introduced by Environmental  Systems Research Institute (ESRI).
    Here is a link to technical whitepaper for the Shapefile format. This information is in portable  document format (PDF). Reading it requires an Acrobat Reader plug-in for your web browser.  Here is a link to download Acrobat Reader.
    
2. We also make most of these map layers available in the Topological Vector Profile of the Spatial Data Transfer Standard (SDTS).
    
3. A limited number of map layers may be made available in Arc/Info Export or Geodatabase formats.
    
4. Some map layers are actually images. These are distributed in GeoTIFF format.
    
5. Sometimes, what appears to be a map layer is not a map layer at all. That's true of the data tables that contain information about the occurrence of moths and butterflies in the  United States. These tables are released in the dBase file format. They can be used in any  software programs (such as spreadsheets and data base managers) that can read a generic dBase file. However, if you want to map this information (using a desktop mapping program, for instance), you must use these data tables in conjunction with the County Boundaries map layer since the species occurrence information is recorded by county.
    

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When I decompress a Shapefile map layer, I get four separate files. What are these?
An ESRI Shapefile consists of a main file, an index file, and a dBASE table; we have added a fourth file that provides a map layer's raw data documentation. The main file, the index file, the dBASE file, and the description file all have the same prefix ("airprtx020," for example). The suffix for the main file is ".shp". The suffix for the index file is ".shx". The suffix for the dBASE table is ".dbf". And the suffix for the metadata file which describes the data is ".met" and ".txt".

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What kind of software do I need to do anything with these map layers?
The map layers can be used in desktop mapping, computer-aided drafting and design, image processing, and in geographic information systems. These files will not work with many common types of software you may use at home or in the office (including word processors, spreadsheets, and data base managers). We have provided a basic online geographic information system (GIS) that allows you to view and query the map layers using your web browser. Follow this link to the National Atlas of the United States Map Maker.

A useful list of third party data conversion tools for GIS files can be found at http://www.grime.net/gistools/index.htm. This site also provides links to an extensive list of software tools that are used to read and write common GIS data formats.

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Who sells software that supports map layers in the Shapefile format?
The following organizations have products that allow you to open, translate, manipulate, analyze, and/or display National Atlas map layers in the Shapefile format. We list the organization name first and then the titles of any software products that are known to (at a minimum) read Shapefiles. We suspect this list is not complete and welcome any information we can use to update the list.
Argus Interware, Incorporated -- Argus ONE
Autodesk, Incorporated -- AutoCADMap, Autodesk MapGuide, AutodeskWorld
Avenza Systems, Incorporated -- MAPublisher
Bentley Systems, Incorporated -- MicroStation GeoGraphics
Caliper Corporation -- Maptitude, TransCAD, Maptitude for the Web, Maptitude for Great Britain
Cadcorp, Incorporated -- Cadcorp SIS
Clark Labs, Clark University -- Idrisi Kilamanjaro, CartaLinx
ComGrafix Technologies, Incorporated -- MapGrafix GIS, GeoInsight for RagTime
Earth Resource Mapping -- ER Mapper (free download)
Environmental Systems Research Institute (ESRI) -- ArcExplorer (free download), Arc/Info, ArcView, AtlasGIS
Geographic Resources Analysis Support System (GRASS) (free download)
Global Mapper Software LLC -- Global Mapper (free download)
Intergraph Corporation -- GeoMedia, GeoMedia Pro, Modular GIS Environment
Manifold Net Ltd. -- Manifold System GIS
MapInfo -- MapInfo Professional, Other mapping products
Map Maker Desktop Mapping -- Map Maker Gratis (free download), Map Maker Pro
MicroImages -- TNTmips, TNTedit, TNTview, TNTlite (free download)
Minnesota Planning Land Management Information Center -- EPPL7
PCI Geomatics Group Incorporated -- Freeview (free download), Geomatica 9
Tachyon Unit -- Locatable, VOICE
Keigan Systems, Incorporated -- MFworks
United States Army Corps of Engineers Coastal and Hydraulics Laboratory -- Groundwater Modeling System (GMS)
United States Geological Survey -- dlgv32 Pro (free download)
United States Naval Academy, Department of Oceanography -- MICRODEM (free download)

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Who sells software that supports map layers in the SDTS Topological Vector Profile format?
The following organizations have products that allow you to open, translate, manipulate, analyze, and/or display National Atlas map layers in the SDTS-TVP format. We list the organization name first and then the titles of any software products that are known to (at a minimum) read SDTS-TVP transfers. We suspect this list is not complete and welcome any information we can use to update the list.
Avenza Systems, Incorporated -- MAPublisher
Cadcorp, Incorporated -- Cadcorp SIS
Caliper Corporation -- Maptitude, TransCAD, Maptitude for the Web, Maptitude for Great Britain
Clark Labs, Clark University -- Idrisi Kilamanjaro, CartaLinx
Environmental Systems Research Institute (ESRI) -- Arc/Info
Geographic Resources Analysis Support System (GRASS)(free download)
Global Mapper(free trial download)
Intergraph Corporation -- Modular GIS Environment
Manifold Net Ltd. -- Manifold System GIS
MicroImages -- TNTmips, TNTedit, TNTview
United States Geological Survey -- dlgv32 Pro (free download)

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Who sells software that supports map layers in the Arc/Info Export format?
The following organizations have products that allow you to open, translate, manipulate, analyze, and/or display National Atlas map layers in an Arc/Info Export format. We list the organization name first and then the titles of any software products that are known to (at a minimum) read Export files. We suspect this list is not complete and welcome any information we can use to update the list.
Bentley Systems, Incorporated -- MicroStation GeoGraphics
Cadcorp, Incorporated -- Cadcorp SIS
Caliper Corporation -- Maptitude, TransCAD, Maptitude for the Web, Maptitude for Great Britain
Earth Resource Mapping -- ER Mapper (free download)
Environmental Systems Research Institute (ESRI) -- Arc/Info, ArcView, MapObjects
Geographic Resources Analysis Support System (GRASS) (free download)
Global Mapper (free trial download)
Manifold Net Ltd. -- Manifold System GIS
MicroImages -- TNTmips, TNTedit, TNTview
PCI Geomatics Group Incorporated -- Freeview (free download), Geomatica 9
United States Geological Survey -- dlgv32 Pro (free download)

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Some map layers, such as Butterfly, are listed as "DBF" files. What are these?
Using the online, interactive National Atlas Map Maker, you can select and display maps of butterfly and moth occurrences by county. These maps are creating by using data tables containing information about moths and butterflies in conjunction with a map layer that shows county boundaries. These "DBF" files are data tables that contain information about all butterfly or moth species in America, by county. These tables are used in conjunction with one of the County Boundaries map layers to map the occurrence of moths and butterflies throughout the United States. In order to use these tables within a desktop mapping or geographic information system, you must also download a County Boundaries map layer and use a relational data base manager to relate or join the map layer to the appropriate table. For more detailed information about the relationship between our County Boundaries map layers and the butterfly and moth occurrence tables, please review their information files shown in the first and third columns of the Raw Data Download Table.

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Some map layers, such as Land Cover Diversity, are listed as "GeoTIFF" files. What are these?
Some National Atlas maps are actually images. Image data may also be referred to as raster data. An image consists of regularly spaced squares (also known as pixels) in which a value is assigned to each square. Each of these squares represents an area on the ground. The values can represent any characteristic assigned to that square such as an index of land cover diversity, elevation, or annual precipitation.

GeoTIFF is an acronym for georeferenced tag image file format. The Tagged Image File Format (TIFF) is a commonly used format for storing map images. GeoTIFF refers to TIFF files which have geographic information embedded within the TIFF file. This geographic information can then be used to position the image in its correct location in the world and on the screen of a geographic information display.

TIFF and GeoTIFF are supported by most image processing programs, such as PhotoShop and ERDAS.

You may follow this link for technical information about the GeoTIFF file format.

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I am using ESRI's ArcGIS to view a National Atlas raw data file in GeoTIFF format. Do you have a projection file I can use?
Yes. For the images we distribute in the Lambert Azimuthal Equal Area map projection, following is a link to text you can cut and paste into a blank document and save it in the ArcGIS Coordinate Systems directory on your computer.

Here is the text for the Lambert Azimuthal Equal Area map projection definition.

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I am using ESRI's ArcGIS to view an Atlas shapefile (.shp). Do you have a projection file I can use?
Yes. National Atlas shapefiles are distributed in a geographic coordinate system and all the necessary projection information is listed in each shapefile's raw data documentation file.

Here is the projection definition that can be used with ESRI's ArcGIS.

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Wow! When I decompressed the Principal Aquifers map layer in SDTS format I got 29 files. What are these?
One of these is a metadata file that provides detailed information about the map layer. In the National Atlas, we also call these raw data documentation files. Another of the 29 files is a brief descriptive text file called README that is required by the Spatial Data Transfer Standard. The remaining files are modules of a topological vector profile SDTS transfer. Follow this link for technical information about the SDTS.

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Can I order the map layers on disc or tape?
No. Map layers from the National Atlas of the United States are no longer available on compact disc or digital versatile disc.

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How can I understand your file naming conventions?
We currently use a ten character file naming convention for map layers in the Shapefile format. Let's use the Federal and Indian Lands map layers to illustrate its use. The first six of the ten characters before the "dot" are reserved for unique, somewhat descriptive, file names (fedlan ). The seventh character indicates whether the map layer contains area features, linear features, point features, etc. The letter "p" as the seventh character (fedlanp) indicates that this map layer includes Federal and Indian Lands areas (polygons). The letter "l" (fedlanl) indicates that this map layer includes linear Federal and Indian Lands, such as parkways and scenic rivers. An "x" as the seventh character in a file name (fedlanx) indicates that the map layer contains data with so little area extent that it is represented by points. Raster data sets can be identified with an "i" for" image" or the letter "g" for "grid." The last three characters (eight through ten) in a file name are reserved for an indication of map scale. A value of 005 indicates a scale of 1:500,000 while a value of 020 indicates data at a scale of 1:2,000,000. A value of 025 indicates data at a scale of 1:2,500,000. A value of 075 indicates a scale of 1:7,500,000 and a value of 150 indicates a scale of 1:15,000,000. The file name appendage (the three characters after the "dot") are assigned by whoever produces the map layer. It is normally used to indicate file type. For example, a small Arc/Info Export file will always have a file name appendage of ".E00."

The file naming convention required by the SDTS Topological Vector Profile is far more rigid. Here, we can use only the first four characters in a mandatory "eight dot three" (8.3) file naming convention. We use the first three characters as the unique file name. The fourth character indicates topology (p = polygon, l = line, m = mixed, x = point, i = image, and g = grid).

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What is "metadata?"
Metadata is "data about data." National Atlas map layers are georeferenced. That is, the lines, points, and areas on our maps refer to some specific place on the Earth's surface. For a digital map, satellite image, or other georeferenced information to be useful it may be necessary to know its name, location, author or source, date, data format, resolution, etc. The Federal Geographic Data Committee (FGDC) is working with industry and state and local government to develop voluntary standards for metadata. The FGDC developed and published the Content Standard for Digital Geospatial Metadata. When you download and decompress a National Atlas map layer, the file whose name ends with ".met" or ".txt" is a metadata file that conforms to this FGDC standard. You may also display a hypertext markup language (HTML) version of this file by clicking on the file name shown in the third column of the Raw Data Download Table. We prefer to refer to these as "raw data documentation files."

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Why is there more than one map layer for some themes (such as water features)?
On maps, some features in the real world are represented by enclosed areas, some features are represented by lines, and some are represented by points. For example, a large lake may be drawn as an enclosed area (often tinted blue), a stream may be symbolized as a line, and a spring may be represented as a single point.  A shapefile can only contain one type of feature, points, lines, or areas.  This means that for some of the themes there are multiple map layer shapefiles bundled in the compressed file. 

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Can I get the 2002, 2003, or 2004 West Nile Virus data?
The data used to create the maps is not available for release by either the National Atlas or the USGS. The data is obtained from CDC. CDC, in turn, obtains the data from state health departments that have agreed with CDC on public dissemination of that data in certain forums: USGS maps, the Morbidity and Mortality Weekly Report (MMWR), the CDC web site, and select scientific publications. For more information please contact the Centers for Disease Control West Nile Virus Surveillance Team (email: dvbid@cdc.gov).

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How can I learn more about the National Atlas of the United States?
Click on this link to the National Atlas of the United States home page.

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