GAP Frequently Asked Questions Sunday, May 19, 2002
What is GAP data?
For what can it be used?

The USGS has a site dedicated to the National GAP Analysis Program. Visit to find the answer to these questions and more.

Who created the GAP data for Louisiana?
The USGS National Wetlands Research Center (NWRC) with others created the GAP data for Louisiana. For information specific to GAP data for Louisiana, visit
How can I view the GAP data? The GAP data is in a TIF file. Any program that can read a TIF file can view the GAP data. You can also see the GAP data online by using Atlas's Rasterviewer by setting its background to "GAP Data"
Can the GAP data be used with a GIS? Yes! The TIF images are registered. ESRI world files (.tfw) are included. Also, Intergraph Geomedia coordinate system files (.csf) have been added.
What is the projection of the GAP data? The TIF files are in UTM zone 15 north, North American Datum 1927, ground units of meters.
What do the colors of the GAP data mean? Each color stands for a category. See the legend in "gapleg.jpg" file and a a description of each category in "descrip.txt". Both files are found in each downloadable Winzip file. The legend is also displayed under the map when GAP data is displayed as the background for Atlas's Rasterviewer.
What are the limits of the usage of the GAP data? Every map has its limit for usage. For more information about the limit of the GAP data, visit to see the disclaimer. (This file has also been included with each Winzip archive file.)
Where can I get more information about GAP data? One way to get more information is to visit the GAP page on the NWRC site Another way is to review the GAP FAQ file by clicking on lagap.html. This file is also included with every downloadable Winzip archive file.