A comprehensive assessment of interpolation methods for regional augmented PPP using reference networks with different scales and terrains

Abstract

Precise point positioning based on RTK networks (PPP-RTK) gives users centimetre-accuracy position solutions in a few seconds. The selection of the interpolation method is one of the critical issues of regional augmented PPP, an approach of PPP-RTK. A proper interpolation algorithm is the basis of reliable interpolated corrections. Although scholars have done a great deal of research on interpolation methods for network RTK, problem of choosing the optional algorithm still remains in the regional augmented PPP based on the SSR concept. Only after each error correction has been matched with a proper interpolation method according to their characteristics, the advantage of SSR can be fully realized and users can obtain corrections for best positioning accuracy. To address this problem, first, the quality of interpolated ionospheric and slant tropospheric corrections of the Distance-Based Linear Interpolation Method (DIM) and six Low-Order Surface Models (LSM) is compared, respectively. Secondly, the observations from large-scale, small-scale, and mountain area networks are utilized to conduct the experiments in order to evaluate the impact of various conditions of the reference station network on the interpolation corrections. The experiment results show that the LSM model with one height component and three horizontal components has the best adaptability to different observation situations. In addition, for the networks with 100 km inter-station distance, 7 or 8 evenly distributed reference stations are enough to provide users with favorable regional augmented PPP service. The results of experiments also show that, during the ionosphere inactive period, the regional augmentation service is still available for the out-of-network users who are about 36 km away from the nearest reference station.