  We consider the problem of carrier-phase differential GPS positioning for an
land vehicle navigation system (LVNS), tightly coupled with an inertial
measurement unit (IMU) and a speedometer. The primary focus is to apply
Bayesian network to an IMU-aided GPS positioning system based on carrier-phase
differential GPS. We describe the implementation details of the positioning
system that integrates GPS measurements (i.e., pseudo-range, carrier-phase and
doppler), IMU measurements, and speedometer measurements. We derive the
linearized state process equation and the measurement equation for GPS and
speedometer. To account for constraints of land vehicle, we add two more pseudo
measurements to ensure the perpendicular velocities close to zero.
