All GPS coordinates are tagged with the following codes:
   FC - Coords have been field checked by CavesR4All and should be dead on
   USGS - Coords were taken from USGS map data, accurate to within 100 ft.
   OMS - Coords were taken from other map sources, accurate to within 100 ft.
   GTA - General target area, coords may be off by as much as 600 ft.