Global PPP-RTK Method Based on GRO and LRO

The construction of global high-precision atmospheric delay model is the key and bottleneck problem for global PPP-RTK applications. In order to overcome the problems of large-scale construction of ground stations as well as difficulties in building stations at sea, a global PPP-RTK method based on GRO (GNSS Radio Occultation) and LRO (LEO Radio Occultation) is proposed. Firstly, the mathematical model of occultation events is studied, and then the number distribution and spatio-temporal resolution of GRO and LRO events are analyzed. The proposed LEO constellation can cover the area of 60 degrees S-60 degrees N in real time with the spatio-temporal resolution for GRO and LRO occultation events, and finally the PPP-RTK positioning is verified based on the atmospheric delay model of GRO and LRO, GNSS and GNSS+LEO convergence time are reduced by 58% and 46%, respectively compared with the PPP positioning.