Impact of elevation mask on multi-GNSS precise point positioning performance

Precise point positioning (PPP) is famous for its capability of high-precision positioning and its wide application in many fields. With the rapid development of BDS and Galileo, the number of GNSS satellites used for positioning has now exceeded 110. It brings both opportunities and challenges to PPP. Based on the data of 90 tracking stations of MGEX, this paper analyzed the impact of elevation masks on the performance of multi-GNSS kinematic PPP. The results show that the PODP increases as the elevation mask increases. In general, it will reduce the positioning accuracy and the convergence speed with the increasing of the elevation mask for the PPP float solution. Furthermore, when the elevation mask is below 25^o, increasing the elevation mask has little effect on the position accuracy of the horizontal and vertical components in the first 10 min. But after 15 min, the effect on the vertical component became apparently. And after convergence, the RMS of multi-GNSS PPP float solution can reach 5 cm and 10 cm for the horizontal and vertical components when the elevation mask is below 25^o. When the elevation mask is 30^o, the RMS is still less than 6 cm for the horizontal component, while about 99% of the RMS is less than 11.5 cm for the vertical component. Thirdly, for multi-GNSS PPP AR, it can improve the TTFF and the fixing percentage by fixing the ambiguity subnet with higher elevation mask firstly. Moreover, when the elevation mask is below to 20^o, the improvement is more obvious and when the elevation mask is larger than 25^o, the TTFF may become longer in some cases.