Low-cost PPP/INS Integration for Continuous and Precise Vehicular Navigation

In recent years, single-frequency Precise Point Positioning (SF-PPP) has become an interesting research topic as most of the low-cost GNSS receivers in the mass market are only providing single-frequency observations. SF-PPP can provide sub-meter accuracy in benign GNSS conditions; however, this accuracy degrades in challenging environments where the GNSS signal is degraded or totally blocked. For a reliable and continuous navigation solution, SF-PPP is integrated with an Inertial Measurements System (INS). This paper presents a low-cost PPP/INS integrated navigation solution targeted for land vehicular navigation. The INS utilizes a full MEMS Inertial Measurement Unit (IMU) to achieve the target low-cost requirements. To tackle the problem of INS drift errors, the system depends on utilizing the PPP accuracy and applying a reliable estimation algorithm. In normal conditions, SF-PPP precise solution dominates the overall system performance. Moreover, it leads to faster convergence and more accurate estimation of IMU sensors biases. The correct estimation of the IMU biases is a vital factor for the integrated system performance in challenging environments and long GNSS outages. The system is evaluated through two road tests which included open-sky, sub-urban, momentary outages, and complete GNSS outage conditions. The results show that the presented PPP/INS maintained horizontal sub-meter rms accuracy in open-sky and sub-urban conditions with results comparable to the u-blox untethered dead reckoning solution (UDR). In a complete GNSS outage of 3 min, in an underground parking, the presented system outperformed the UDR solution and showed a better long-term performance. The presented system is expected to benefit low-cost precise land vehicle navigation applications.