This dissertation develops a low-cost integrated navigation system, which integrates multi-constellation global navigation satellite system (GNSS) precise point positioning (PPP) with a low-cost micro-electro-mechanical sensor (MEMS)-based inertial system for precise applications. Both undifferenced and between-satellite single-difference (BSSD) ionosphere-free linear combinations of pseudorange and carrier phase measurements from three GNSS constellations, namely GPS, GLONASS and Galileo, are processed. An improved version of the PF, the unscented particle filter (UPF), which combines the UKF and the PF, is developed to merge the corrected GNSS satellite difference observations and inertial measurements and estimate inertial measurements biases and errors. The performance of the proposed integrated system is analyzed using real test scenarios.
A tightly coupled GPS PPP/MEMS-based inertial system is first developed using EKF, which shows that decimeter-level positioning accuracy is achievable with both undifferenced and BSSD modes. However, in general, better positioning precision is obtained when BSSD linear combination is used. During GPS outages, the integrated system shows submeter-level accuracy in most cases when a 60-second outage is introduced. However, the positioning accuracy is improved to a few decimeter- and decimeter-level accuracy when 30- and 10-second GPS outages are introduced, respectively. The use of UPF, on the other hand, reduces the number of samples significantly, in comparison with the traditional PF. Additionally, in comparison with EKF, the use of UPF improves the positioning accuracy during the 60-second GPS outages by 14%, 13% and 15% in latitude, longitude and altitude, respectively. The addition of GLONASS and Galileo observations to the developed integrated system shows that decimeter- to centimeter-level positioning accuracy is achievable when the GNSS measurement updates are available. In comparison with the GPS-based integrated system, the multi-constellation GNSS PPP/MEMS-based inertial system improves the latitude, longitude and altitude components precision by 24%, 41% and 41%, respectively. In addition, the use of BSSD mode improves the precision of the latitude, longitude and altitude components by 23%, 15% and 13%, respectively, in comparison with the undifferenced mode. During complete GNSS outages, the developed integrated system continues to achieve decimeter-level accuracy for up to 30 seconds, while it achieves submeter-level accuracy when a 60-second outage is introduced.