How NLOS Signals affect GNSS relative positioning

Owing to the existence of non-line-of-sight (NLOS) signals in global navigation satellite system (GNSS) challenged environment, the accuracy of GNSS relative positioning is seriously damaged. This paper demonstrates the effects of NLOS measurement error on GNSS relative positioning for short-baseline in both theory and field test. The results show that the effects of NLOS signal in both pseudorange and carrier phase make the ambiguity unable to be successfully fixed. In addition, we have found that after removing the labelled NLOS observations, the positioning accuracy can be significantly improved. The more the available LOS satellites, the more the robustness against NLOS satellites of the ambiguity resolution. This implies that GNSS Multi-Frequency Multi-System technology might improve the performance of GNSS relative positioning because there would be sufficient LOS signals after the NLOS signals are removed.