联合GEO/IGSO/MEO的北斗PPP模糊度固定方法与试验分析

Abstract

由于北斗地球静止轨道(geostationary earth orbiting，GEO)卫星轨道精度较低且其观测值受多路径误差和伪距偏差影响严重，目前各分析中心尚未针对北斗GEO卫星提供长期稳定的相位小数偏差(uncalibrated phase delay，UPD)产品，北斗精密单点定位(precise point positioning，PPP)模糊度固定技术研究主要针对倾斜轨道(inclined geosynchronous orbiting，IGSO)和中地球轨道(medium earth orbiting，MEO)卫星。本文采用Wanninger和Beer的高度角模型消除了IGSO/MEO观测值伪距偏差，并通过小波变换提取低频分量修正伪距观测值的方法削弱了GEO卫星多路径和伪距偏差的影响。由于窄巷UPD估值受未模型化误差影响较大，本文改进了窄巷UPD估计的策略，该策略利用上一历元成功估计的窄巷UPD对当前历元的浮点模糊度进行改正，剔除了残差较大的浮点模糊度，修正固定错误的整周模糊度，从而提高了窄巷UPD的精度和稳定性。利用估计得到的UPD产品，本文实现了联合GEO、IGSO和MEO卫星的北斗非差PPP模糊度固定，并对其定位性能进行分析。结果表明:联合GEO、IGSO和MEO卫星的PPP固定解的首次固定时间和收敛时间均可以缩短到30 min以内; 6 h后的E、N、U方向的定位误差由(1.35、0.35、2.75)cm减少到(1.07、0.26、2.24)cm，分别减少了20%、27%和18%。

Alternate abstract:

Since the precision of GEO satellite orbit is low and the observations of GEO are affected seriously by the multipath and code bias, now no analysis center in the world provide the uncalibrated phase delay (UPD) products of BeiDou Satellite Navigation System (BDS) GEO satellites. At present, the BDS precise point positioning (PPP) ambiguity resolution (AR) for global users still limits on the IGSO and MEO satellites. In our study, we eliminated the code bias of IGSOMEO satellite by using the elevation-dependent model proposed by the Wanninger and Beer and the code bias of GEO satellite was corrected by the wavelet transform. We also improve the method of NL UPD estimation by applying accurate UPDs estimated in last epoch to select the correct ambiguities at current epoch. Once we obtain the high-quality UPD products, the BDS PPP ambiguity resolution with GEOIGSOMEO satellites is achieved and then the performance of the PPP AR results is evaluated. Results show that:The convergence time and the time to first fix are both less than 30 min for BDS PPP ambiguity resolution with GEOIGSOMEO satellites. The positioning error based on six-hour observations for East, North and UP direction are reduced by 20%, 27% and 18% (from 1.35, 0.35 and 2.75 cm to 1.07, 0.26, and 2.24 cm).