Those of you interested in pursuing GPS for various surveying projects should check out the maritime navigation sources, and fully understand the differential gps issue. (The DOD has intentionally degraded the accuracy of GPS, but there is a calibration work around.) For more than just recording where you are, I highly recommend a unit with a full numberical keypad for entry of lat long survey points etc. There are interfaces to marine chart software for both the Mac and IBm available, but I suspect taht no one has yet started loading topo maps or ordnance survey maps ( at least off the shelf). Benj. A.G.Fuller seabag enterprises [log in to unmask]