The Quasi-Zenith Satellite System (QZSS) is a regional system with four-satellite constellation, operated by the government of Japan. The system offers highly precise and stable service in the Asia-Oceania region, compatible with Global Navigation Satellite System (GNSS). The Centimeter Level Augmentation Service (CLAS) is one of the services of QZSS which provides compact Space State Representation (SSR) correction messages to the users through the L6 band signal. CLAS messages cover all over Japan, and they consist of 19 networks and 231 grid points. CLAS compact SSR correction messages include GNSS orbit correction, GNSS clock correction, GNSS signal bias, STEC correction and Gridded correction and so on and they are used as a technique to improve the accuracy of Precise Point Positioning (PPP). In the current study, we decoded the CLAS messages and performed PPP based on pseudo-range measurements. As a result, we achieved 37-49 cm accuracy in an open-sky environment where multipath errors rarely occur. Analysis results are much better than the results obtained through the Standard Point Positioning (SPP).

Keywords: PPP, QZSS, CLAS, Compact SSR, pseudorange