In one embodiment, a geographic-positioning component records a first location of a mobile device. The geographic-positioning component determines on a periodic basis a current location of the mobile device. The geographic-positioning component determines whether the current location is outside a geographic region defined at least in part by the first location and a radius, the radius being adjusted from a pre-determined value based on a detected velocity of the mobile device; time of day information; a battery level of the mobile device; or an error of the first location measurement or the current location measurement. If the current location is outside the geographic region, the geographic-positioning component causes a client application of the mobile device to send the current location to a remote server.