Performance Evaluation and Future Application of Real-Time PPP Product in Japan

Abstract

Quasi-Zenith Satellite System (QZSS) is a Japanese satellite navigation system developed by Japan Aerospace Exploration Agency (JAXA). Besides transmitting conventional positioning signals, QZSS also transmits augmentation signals to enhance the performance of the global navigation satellite system (GNSS). One of the QZSS augmentation signals is the L-band experimental (LEX) signal. The LEX signal is designed to transmit multi-GNSS precise orbit and clock corrections for enabling real-time precise point positioning (PPP) to obtain high-accuracy positioning. The real-time PPP product is called “Multi-GNSS Advanced Demonstration tool for Orbit and Clock Analysis” (MADOCA). Since PPP does not require a reference station, several applications based on it are expected to develop. In this paper, we introduce two experiments; one is longterm performance evaluation at sea, and the second is the use of precise orbit and clock for cars in urban areas to achieve decimeter level accuracy using dual-frequency observations. First, we performed an experiment using the real-time PPP product by MADOCA at sea and verified the positioning accuracy. At present, it is impossible to process the ambiguity resolution for the real-time PPP product by MADOCA. Therefore, we verified the positioning rate and positioning accuracy using the PPP float solution. The experimental results indicated that it was possible to provide approximately 92% of the positioning rate and approximately 10 cm level within a service area. Second, the use of precise orbit and clock for cars in urban areas was investigated. Even with a low-cost singlefrequency receiver, the horizontal positioning accuracy was ~50 cm (RMS error). This result indicates that the pseudo-range-based positioning using the MADOCA product and dual frequency receiver could achieve the same level of positioning rate as the differential technique. If it can be demonstrated reliably, the service areas of the decimeter level accuracy can be extended widely without installing reference station’s data.