The Research Of Multi-GNSS Combined PPP Algorithms

Due to the simple and free mode of operation and one can achieve static and kinematic positioning in global and get the precise coordinates within ITRF reference frame directly using only one single receiver,Precise Point Positioning(PPP)has been widely used in low-orbit satellite orbit determination,GPS Meteorology,high-precision positioning,GPS seismology,high-precision ionosphere modeling and other fields.However,there are still some shortcomings in PPP,such as the slow convergence speed,the difficulties in PPP ambiguity resolution(AR)and lower positioning performance under complicated observation conditions.At present,GLONASS has been completed full of constellation operation and China's BeiDou satellite system(BDS)has provided services to Asia-Pacific region since the end of 2012.The multi-GNSS combined research has become a hotpot.Thus,this paper researched the theory of PPP ambiguity resolution and multi-GNSS combined PPP.The positioning performance of multi-GNSS combined PPP and the time to first fix and the positioning accuracy in short time of GLONASS/BDS aided GPS PPP AR are analyzed.The main work of this article are listed below:(1)Achieved the GPS PPP ambiguity resolution based on integer-phase clock.Using the satellite wide-lane biases and integer-phase clocks of CNES,the ambiguities of GPS single-difference PPP between satellites are successfully fixed.And the positioning accuracy in short time are significantly improved after ambiguity fixed.Under the circumstances of new satellite arise or cycle-slip happens on one satellite,the ambiguity of this satellite will re-convergence.The ambiguity which hasn't convergence will affect the resolution of other ambiguities.Then,a partial ambiguity resolution method which take into account the quality control is adopted.This method can control the affect the ambiguities which haven't convergence effectively and improve the ambiguity fix rate.(2)Researched the theory of multi-GNSS combined PPP,analyzed the positioning performance in static,kinematic mode and under different cut-off elevation situations of multi-GNSS combined PPP.The conclusions have shown that the multi-GNSS combined PPP can improve the convergence speed and positioning accuracy in short time,but affect little on long time positioning accuracy.(3)Achieved the GLONASS/BDS aided GPS PPP ambiguity resolution.The experiments have shown that time to first fix is shorter and ambiguity fix rate is improved with GLONASS/BDS aided.