Precise point positioning for mobile robots using software GNSS receiver and QZSS LEX signal

This paper describes outdoor localization for a mobile robot using precise point positioning (PPP) based on the Quasi-Zenith Satellite System (QZSS) L-band Experiment (LEX) signal. For autonomous navigation applications, a real-time kinematic (RTK) global positioning system (GPS) technique is widely used to estimate user position with high-precision accuracy in real time. However, RTK-GPS requires a reference station, and there are data acquisition costs involved in estimating the position. Our approach corrects position error by applying PPP using the QZSS LEX message. PPP can estimate a single receiver position without any reference station or baseline, through use of satellite position fixing and clocks. We developed a method for extracting the QZSS LEX message in real time using a software GNSS receiver. We then constructed the PPP framework based on an LEX message containing the satellite ephemeris and clock errors. Finally, we conducted field experiments to evaluate the accuracy and precision of our proposed method. The experimental results confirmed that our method made a localization precision of 1.29 m possible without using a GNSS reference station.