Abstract
Abstract The release of low-cost dual-frequency (DF) global navigation satellite system (GNSS) modules provides an opportunity for low-cost precise positioning to support autonomous vehicle applications. The new GNSS modules support the US global positioning system (GPS) L1C/L2C or L5 civilian signals, the Russian GNSS Globalnaya Navigazionnaya Sputnikovaya Sistema (GLONASS) L1/L2, Europe’s GNSS Galileo E1/E5b, and Chinese GNSS BeiDou B1/B2 signals. The availability of the DF measurements allows for removal of the ionospheric delay, enhancing the obtained positioning accuracy. Unfortunately, however, the L2C signals are only transmitted by modernized GPS satellites. This means that fewer GPS DF measurements are available. This, in turn, might affect the accuracy and the convergence of the GPS-only precise point positioning (PPP) solution. Multi-constellation GNSS PPP has the potential to improve the positioning accuracy and solution convergence due to the high redundancy of GNSS measurements. This paper aims to assess the performance of real-time quad-constellation GNSS PPP using the low-cost u-blox Z9D-F9P module. The assessment is carried out for both open-sky and challenging environment scenarios. Static, simulated-kinematic, and actual field-kinematic trials have been carried out to evaluate real-time PPP performance. Pre-saved real-time precise orbit and clock products from the Centre National d’Etudes Spatiales are used to simulate the real-time scenario. It is shown that the quad-constellation GNSS PPP using the low-cost u-blox Z9D-F9P module achieves decimeter-level positioning accuracy in both the static and simulated-kinematic modes. In addition, the PPP solution convergence is improved compared to the dual- and triple-constellation GNSS PPP counterparts. For the actual kinematic trial, decimeter-level horizontal positioning accuracy is achieved through the GPS + GLONASS + Galileo PPP compared with submeter-level positioning accuracy for the GPS + GLONASS and GPS + Galileo PPP counterparts. Additionally, submeter-level vertical positioning accuracy is achieved through the GPS + GLONASS + Galileo PPP compared with meter-level positioning accuracy for GPS + GLONASS and GPS + Galileo PPP counterparts.
Highlights
The precise point positioning (PPP) technique is attractive to the global navigation satellite system (GNSS) community due to its high precision without the need for additional base station infrastructure
The improved robust adaptive Kalman filter (IRKF) was used as the estimation filter, and the measurements were processed in different modes, namely, real-time global positioning system (GPS) + Globalnaya Navigazionnaya Sputnikovaya Sistema (GLONASS) PPP (GR–PPP), GPS + Galileo PPP (GE–PPP), GPS + GLONASS + Galileo PPP (GRE–PPP), GPS + GLONASS + BeiDou PPP (GRC–PPP), and GPS + GLONASS + Galileo + BeiDou PPP (GREC) modes
The accuracy of the GRE–PPP and GRC–PPP solutions was significantly improved compared with the GREC PPP solution
Summary
The precise point positioning (PPP) technique is attractive to the global navigation satellite system (GNSS) community due to its high precision without the need for additional base station infrastructure. Real-time precise GNSS satellite orbit and clock products have recently become available through the international GNSS service (IGS) and several analysis centers (Wang et al, 2018). This allows users to apply real-time global positioning system (GPS) PPP (Elsobeiey and Al-Harbi, 2016) or multi constellation GNSS PPP (Wang et al, 2018). The positioning performance was slightly improved through real-time SF GNSS PPP with a 30° elevation angle in static and kinematic experiments (de Bakker and Tiberius, 2017)
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