Also, pretty subtle thing.. but places are constantly moving due to plate tectonics and continental drift. A GPS position describing a location will slowly go

Also, pretty subtle thing.. but places are constantly moving due to plate tectonics and continental drift. A GPS position describing a location will slowly go out of date over time. http://en.wikipedia.org/wiki/File:Global_plate_motion_2008-04-17.jpg http://en.wikipedia.org/wiki/File:Global_plate_motion_2008-0...