A mobile terminal that operates in a plurality of position tracking modes. The mobile terminal comprises a Global Positioning System (GPS) unit for receiving GPS signals from a plurality of GPS satellites. The GPS unit can operate in i) a device autonomous fix (DAF) mode, ii) a server-computed assisted fix (SCAF) mode, and iii) a device-computed assisted fix (DCAF) mode. The mobile station also comprises a network transceiver for communicating with at least one terrestrial wireless network and a controller for controlling the operating mode of the GPS unit. The controller transitions the GPS unit between the DAF mode, the SCAF mode, and the DCAF mode. The controller receives an interrupt signal from at least one sensor and, in response, causes the GPS unit to operate in one of the DAF mode, the SCAF mode, and the DCAF mode.