Overlays United States counties, parishes, and certain city border information. After this is done, the basic geography is re-overlaid onto your map. The source file is highly detailed, condensed from U.S. Geological Survey data, and has an accuracy of 1 mile. There are about 175,000 points in this file, so it may takea few minutes to plot on slower computers.
Overlays the actual county lines onto the map. This data is in binary format and is not editable.
Overlays the names of the counties. The names are truncated according to the zoom factor so that they fit within the county. Users can edit the locations of these county labels as well as their text content by editing the plaintext file DIGATMOS.CXT with any text editor (such as Windows Notepad).