I have a Garmin E-Map GPS, which is an older full function GPS. I recently bought the MapSource Topo program for it, (about $120) and is is awesome. If your GPS will support such a program, I highly recommend it. It is not as detail as a 1:24,000 USGS map. The elevations are every 60ft., not 20ft. This is not as defined as a USGS map, but a huge help when out hunting. It will show farm roads, creeks, elevations, and bodies of water that are not on GPS street maps. It is a huge difference. If you have a Garmin, you can view the map program on their website to see if the detail will help you with the area you hunt. I am not sure whats available for other GPS's.