i have been using gps units for years and the combination i have used is garmin and a program called maptech which allows me to print out my own topo maps. i used the gps to locate my postion on the map. now, recently i have been playing around with a magellan sport trak pro which has a build in memory and contains streets and highways, but you can order a program called mapsend topo for the united states and install it to your computer. you can then bring up a location on the map and download it to the gps. by zooming in on the map, you get all the detail you will need and then some, can' t wait to try it out in the field and compare the map in the gps with a hardcopy to see how close they come.