Centimeter Level Augmentation Service (CLAS) in Japaneses Quasi-Zenith Satellite System, its Preliminary Design and Plan

A preliminary design and a plan regarding Centimeter Level Augmentation Service (CLAS) in Japanese Quasi-Zenith Satellite System (QZSS) are introduced. In the service, Centimeter level augmentation information including correction and integrity information is allocated to Japanese QZSS original L6 signal and broadcast to users available for the main islands of Japan and its surrounding ocean area. CLAS is under development and will begin in F.Y.2018 with a four-satellite constellation of QZSS. The correction information includes satellite orbit corrections, satellite clock corrections, satellite code/phase biases, slant ionospheric delay parameters, vertical troposheric delay parameters, which will be a corresponding method “RTK-PPP” defined in the standard RTCM STANDARD 10403.x SSR Messages [1]. The correction information has been designed so that users can obtain their position with centimeter level accuracy, 6 cm (95%) in horizontal and 12 cm (95%) in vertical within 1 minute after they start receiving GNSS signals and L6 signal. With the aim of designing the correction information, we have analyzed the observation data from Japanese electric reference stations and correction information gathered from the application demonstration system (Saito et. al. 2011)[2].We have specified acceptable amount of each factor of the ranging residual error, and designed the temporal and spatial interval of each correction and their numerical resolution, which satisfy the allocated residual error and also adapt to the total data amount of correction information (2kbps). The design has resulted in covering the main islands of Japan and its surrounding ocean area with considering the Japanese geodetic datum, and shortening ambiguity fixing initialization time within 1 minute. Not only survey and disaster monitoring but also in the field of IT-based precise agriculture, construction and Intelligent Transport Systems (ITS) are expected as future applications.