GNSS reliability and positioning accuracy enhancement based on fast satellite selection algorithm and RAIM in multiconstellation

In order to improve the performance of positioning reliability, accuracy, and robustness in Global Navigation Satellite System (GNSS), several special actions, including receiver autonomous integrity monitoring (RAIM), weighted matrix estimation in weighted least squares (WLS), geometric dilution of precision (GDOP) in satellite geometry distribution, need to be taken into consideration in multiconstellation. With the extensive application and popularization of GPS, it makes remarkable contributions to scientific applications and engineering services. Currently, two emerging constellations (BDS, Galileo) as well as the recovery of GLONASS, the multiconstellation GNSS is undergoing dramatic development with better performance. Once the four systems are fully deployed, about 120 satellites will be available for GNSS users [1]. If all the visible satellites are used for position resolving, it will burden the receiver processor significantly. Meanwhile, there may be larger pseudorange measurement errors when the satellites have low elevation for the transmission of ionospheric and tropospheric delay. In addition, we cannot neglect simultaneous multiple outliers in multiconstellation GNSS compared with conventional RAIM. With respect to the weighted matrix factor in WLS, i.e., the uncertainty of the pseudorange measurements, estimation error is often used for weighted matrix estimation, without concerning real-time transmission error and signal quality, which somewhat enlarges the positioning accuracy. Thus, there is a need to deal with the above concerns.