More than 3 Years of Operation Experience for the First Satellite-based Open PPP-RTK Correction Service
Dr. Rui Hirokawa, Mitsubishi Electric Corporation
Since November 2018, Quasi-Zenith Satellite System (QZSS) Centimeter-Level Augmentation Service (CLAS) is operating the first satellite-based open PPP-RTK service for Japan. The application of QZSS CLAS includes automotive, agriculture, construction, and drone. This paper presents the operational experience for more than three years including the severe medium scale traveling ionospheric disturbance (MSTID). The format of correction service is also defined as an open format named Compact SSR which is an efficient format compatible with RTCM SSR. In November 2020, the maximum number of satellites for correction has been increased from 11 to 17 by applying a new message format with the variable bit-length atmospheric delay representation. The statics shows the positioning accuracy of 4cm for horizontal (95%) and the convergence time of 40 sec (95%) have achieved for kinematic application under open-sky condition. This paper also shows the proposals for the improvement of QZSS CLAS to improve security and performance. The proposal to further increase the number of satellites for PPP-RTK correction is based on the geometry-based satellite grouping by introducing the sub-mask to define the group of satellites in nominal and high-elevation angles. A timing-based optimization for multiple channels of QZSS L6D channels is also presented, it was shown that the initial convergence time could be considerably improved.