1. A position tracking device for use in position tracking system, wherein the position tracking device is associated with a mobile object to be tracked by the position tracking system such that the position tracking device moves with the mobile object, the position tracking device including: an inertial sensor assembly; a reference position receiver; and a high resolution module in communication with the inertial sensor assembly and the reference position receiver, wherein the high resolution module is for computing the location of the mobile object in real-time based on a combination of input from the inertial sensor assembly and a reference position signal received by the reference position receiver when the mobile object is located in a first area requiring high position resolution.