Pseudoranges Error Correction in Partial GPS Outages for a Nonlinear Tightly Coupled Integrated System

Integrated navigation systems based on a tightly coupled integration scheme utilize pseudoranges and pseudorange rates from Global Positioning System (GPS) satellites measured by the receiver. The positioning accuracy is highly dependent on the accuracy of the pseudoranges whose residual errors can deteriorate the overall positioning accuracy. The integrated system can be improved by the provision of more accurate pseudoranges through modeling the residual correlated errors. This paper utilizes parallel cascade identification (PCI), which is a nonlinear system identification technique, to model these correlated errors. To address the nonlinear error characteristics in the whole integrated navigation system, a nonlinear filter, i.e., mixture particle filter (M-PF), is employed to perform tightly coupled integration of a 3-D reduced inertial sensor system (RISS) with a GPS. The M-PF can accommodate the PCI models of the pseudorange errors in the measurement model. The results demonstrate the advantages of using M-PF-PCI for correcting the pseudoranges and enhancing the positioning solution as compared with M-PF-only, Kalman filter (KF)-PCI, and KF-only solutions.