基于BDS/GPS双系统的全球电离层建模
摘要
In order to overcome the weakness of GIM based on BeiDou single system and improve the accuracy of GIM and differential code bias (DCB), we created the GIM products based on BDS/GPS dual system assisted with GPS. In this study, we do analysis on the accuracy of GIM based on BDS/GPS and the auxiliary function for DCB monitoring by GPS. The ionosphere observations of BeiDou and GPS over 336 d from February 11, 2013 to January 13, 2014 in solar high activity have been used to generate a set of global ionosphere grids (GIM/SHA) with sphere harmonics at spatial resolution of 15×15 degree and order. The comprehensive accuracy assessment for the GIM/SHA products is provided by using IGS final products (GIM/IGS), real-measured vertical total electron content (VTEC) by dual-frequency observations and VTEC by Jason-2 radar altimetry. Our study reveals: (1) Comparing the VTEC on global grids with that of three kinds of assessment data, the average RMS of GIM/SHA is in the range of 3-6 tecu with a little systematic bias; (2) For the estimated P1P2 DCB of GPS satellites, the bias between GIM/SHA and IGS is within 0.1 ns with RMS less than 0.2 ns; (3) For the estimated B1B2 DCB of satellites and receivers based on BeiDou single system and dual system, the difference of mean values is within 0.01-0.227 ns and the solution based on the dual system is a little better than that based on the single system, but GIM/SHA can obviously improve the stability for receiver DCB by using GPS observations. From the long-term stability statistics for 14 BeiDou satellites' B1B2 DCB, the stability is at 0.2-0.3 ns level, while slightly worse for that of GEO satellites.