Abstract: Aiming at the BDS-3 positioning performance under the condition of low satellite visibility and epoch availability, this paper analyzes different altitude angles (10°, 20°, 30°, BDS-3 and GPS measured data from MEGX tracking station). 40°) SPP positioning accuracy of BDS-3 satellites B1I, B1C, B2a, B3I and GPS system L1 frequency. It is found through research that the average number of visible satellites and satellite spatial geometry of BDS-3 are better than GPS, and it changes linearly with the increase of the altitude angle. The SPP positioning accuracy of the four frequencies of BDS-3 increases first and then decreases with the increase of the altitude angle. When the altitude angle is 20°, the positioning accuracy is the highest. When the altitude angle reaches 40°, the positioning accuracy is the lowest, and the epoch availability rate is also the lowest. But the availability rate of the B1I and B3I epochs is still greater than 90%, while the availability rate of the B1C and B2a epochs is greater than 70%. Both the SPP positioning accuracy and the epoch availability are better than the GPS system L1 frequency.

Key words: BDS-3, SPP, different elevation angles, epoch availability rate