Patent ID: 8374787

Claim:
A mobile navigation device, comprising: a satellite positioning module, for receiving a satellite navigation signal; a dead reckoning module, for detecting a displacement and a rotation of the mobile navigation device; a processor coupled to the satellite positioning module and the dead reckoning module, for reading the satellite navigation signal, the displacement, and the rotation, wherein the mobile navigation device operates in a first mode and a second mode alternately, and in the first mode, the satellite positioning module is activated, the dead reckoning module is disabled, and the processor calculates a position coordinate according to the satellite navigation signal, and in the second mode, the satellite positioning module is disabled, the dead reckoning module is activated, and the processor updates the position coordinate according to the displacement and the rotation; and a memory coupled to the processor, for storing the position coordinate, wherein when the mobile navigation device is switched from the first mode to the second mode, the memory keeps the data status of the satellite positioning module for a next switch back to the first mode from the second mode, wherein in the first mode: the processor determines whether a first time span when the mobile navigation device continuously operates in the first mode exceeds a first threshold time span, the mobile navigation device is switched to the second mode by the processor when the first time span exceeds the first threshold time span, and the processor continues to update the position coordinate according to the satellite navigation signal when the first time span does not exceed the first threshold time span.