The ContourGPS and Contour+ contain a built-in GPS receiver that allows you to capture and share position information from the worldwide network of global navigation satellites. Based on the timing of signal received and the distance calculated from each respective satellite, the Contour cameras are able to accurately track your speed, elevation, and distance, with a small degree of error. 

Contour cameras captures GPS data to an accuracy within 10 meters of your actual location for latitude / longitude ground positioning.  The accuracy for elevation / altitude readings is generally accurate to within 30 vertical meters of your actual elevation or altitude.