USGS 7.5' Map Updates Sunday, November 10, 2002


USGS continually updates its 7.5' topographic map series for the entire nation. In order to keep up with the times, the USGS is now providing the maps as DRG. Recently, the USGS, via the Louisiana Department of Environmental Quality, has provided the latest DRG updates for Louisiana to Atlas. The new DRGs are in Geotif files with accompanying tfw files. FGDC metadata for each DRG gives important information such as when the DRG was updated.

These updated DRG files are available through the 1:24,000 DRG Downloader. The 7.5' quadrangles with updated DRG files are shown in the downloader's index map in a lighter shade of green. The downloader gives the user the ability to download the pre 1998 DRG or the post 1998 DRG. As more of these updated DRGs become available, they will be added to Atlas.

The table below gives the differences between the previously available DRGs and the new, updated DRGs.

Previous DRGs
New, Updated DRGs
Collars (Marginallia) removed maintained
File format and
Geotiff but no accompanying tfw file Geotiff with accompanying tfw file
Metadata none FGDC metadata present
Publication Dates pre 1998 post 1998

See the FGDC metadata for information as to how the DRGs were created. Also, visit for information regarding USGS mapping standards.