I ahve a simple Garmin eTrex that I use to mark spots (waypoints) and I also let it track me sometimes so I can see where I've been. I just downloaded the information onto my computer using the ExpertGPS and it appears to be very accurate. I'm on the 30 day trial, but I can switch between aerial or Topo or you can even submit your own photo i think. I carry a topo map with me and an aerial with me and use that method. GPS is only to mark scrapes, sightings, trails, etc for reference. I personally would always carry a paper copy of the maps even if I had them electronically because you are SOL if the electronics crap out. Always good to have a regular map with you.