I use the GPS waypoint function. Does your GPS have it? I just push a button, and the location and altitude are stored. I then download the waypoints to my computer, and it adds them to my map. I can then zoom in to the map and see the location within a few feet. About batteries: I use a Garmin 60CSx portable GPS. I can mount it to the dash of the car, or remove it and carry it with me. It uses AA batteries. I always keep a battery charger and a bunch of spare batteries with me. The new NiMH batteries will hold a charge just about forever. Also, some portable GPSes have a battery saver option that you can turn on.