Implementation and Analysis of Tightly Coupled Global Navigation Satellite System Precise Point Positioning/Inertial Navigation System (GNSS PPP/INS) with Insufficient Satellites for Land Vehicle Navigation

Abstract

This paper implements and analyzes a tightly coupled single-frequency global navigation satellite system precise point positioning/inertial navigation system (GNSS PPP/INS) with insufficient satellites for land vehicle navigation using a low-cost GNSS receiver and a microelectromechanical system (MEMS)-based inertial measurement unit (IMU). For land vehicle navigation, it is inevitable to encounter the situation where insufficient satellites can be observed. Therefore, it is necessary to analyze the performance of tightly coupled integration in a GNSS-challenging environment. In addition, it is also of importance to investigate the least number of satellites adopted to improve the performance, compared with no satellites used. In this paper, tightly coupled integration using low-cost sensors with insufficient satellites was conducted, which provided a clear view of the improvement of the solution with insufficient satellites compared to no GNSS measurements at all. Specifically, in this paper single-frequency PPP was implemented to achieve the best performance, with one single-frequency receiver. The INS mechanization was conducted in a local-level frame (LLF). An extended Kalman filter was applied to fuse the two different types of measurements. To be more specific, in PPP processing, the atmosphere errors are corrected using a Saastamoinen model and the Center for Orbit Determination in Europe (CODE) global ionosphere map (GIM) product. The residuals of atmosphere errors are not estimated to accelerate the ambiguity convergence. For INS error mitigation, velocity constraints for land vehicle navigation are adopted to limit the quick drift of a MEMS-based IMU. Field tests with simulated partial and full GNSS outages were conducted to show the performance of tightly coupled GNSS PPP/INS with insufficient satellites: The results were classified as long-term (several minutes) and short-term (less than 1 min). The results showed that generally, with GNSS measurements applied, although the number of satellites was not enough, the solution still could be improved, especially with more than three satellites observed. With three GPS satellites used, the horizontal drift could be reduced to a few meters after several minutes. The 3D position error could be limited within 10 m in one minute when three GPS satellites were applied. In addition, a field test in an urban area where insufficient satellites were observed from time to time was also conducted to show the limited solution drift.

Comparison of Kalman Filters for Inertial Integrated Navigation

“…The inertial integrated navigation system has been used in many fields, such as land navigation, underwater navigation, and even aerospace and unmanned system navigation [13,14,15,16,17,18]. For example, these systems are usually integrated with a global positioning system (GPS), Roland C or an odometer for land navigation integration, and integrated with the Doppler Velocity Log (DVL) baseline system for underwater navigation integration.…”

An Improved Multi-Satellite Method for Evaluating Real-Time BDS Satellite Clock Offset Products

“…Such corrections are formatted according to the Radio Technical Commission for Maritime Services (RTCM) state-space representation (SSR) standard and disseminated using the networked transport of RTCM via internet protocol (NTRIP). Based on the RTS products, the precise point positioning (PPP) technology can be processed in real-time mode [1-3], which has been applied to various real-time fields such as vehicle navigation [4], aerial triangulation [5], time transfer [6], and architecture deflection detection [7]. On December 27, 2018, the BeiDou Navigation Satellite System (BDS) started to provide global services.…”

Precise Single-Frequency Positioning Using Low-Cost Receiver with the Aid of Lane-Level Map Matching for Land Vehicle Navigation

“…To overcome the drawbacks in SF-PPP and SF-RTK, the inertial navigation system (INS) is usually integrated with GNSS positioning. Liu et al 2018 tightly integrated SF-PPP and INS for land vehicle navigation in a challenging environment. Han et al 2017 and Li et al 2017 integrated inertial measurements to aid SF-RTK ambiguity resolution (AR), which effectively improves the successful fixing rate.…”