Design of Integrity Function on Centimeter Level Augmentation Service (CLAS) in Japanese Quasi-Zenith Satellite System

Centimeter Level Augmentation Service (CLAS) in Japanese Quasi-Zenith Satellite System (QZSS) is under development and will begin in 2018 with a four satellite constellation. The outline of the service, contents of the broadcast augmentation information, a design framework for constructing a satellite based RTK-PPP (Real Time Kinematic Precise Point Positioning) service were presented in ION GNSS+ 2014 [1]. A signal design, a user interface design, and a message standardization plan for CLAS were presented in ION GNSS+ 2015 [2]. In this paper, new topics concerning a design of integrity function for CLAS is described. To realize the practical application of CLAS, it is necessary to detect an abnormal signal caused by a faulty satellite or by an irregular ionospheric or tropospheric characteristic at every epoch in real time as the integrity function. We show the status of system design of CLAS in consideration with the integrity function.