北斗广播星历偏差分析及改正

以后处理精密轨道钟差为参考,分析了2014年2月至2016年10月北斗广播星历误差及空间信号精度,分析结果表明,北斗广播星历存在偏差,最大超过2m。在此基础上,基于广域差分改正数,采用18个MGEX站不同频点及频点组合连续97d的数据对以上广播星历偏差进行了进一步验证。验证结果表明,不同卫星的伪距观测残差存在与广播星历偏差一致的系统性偏差。比较后处理给出的TGD和广播星历给出的TGD参数的偏差(dTGD),发现dTGD与基于广域差分参数的BEB的相关系数达到0.89,这表明经广域差分参数改正后的星历偏差可能是由广播电文中的TGD偏差造成。将北斗广播星历偏差改正到TGD参数上,分析对用户定位的影响。结果表明,经改正后,双频用户在N、E、U 3个方向单点定位精度分别提高14.9%、28.4%、15.5%,其定位残差也明显得到改善。

Analysis and Application of BDS Broadcast Ephemeris Bias

We analyze the BeiDou broadcast ephemeris biases starting from February 2014 to October 2016 by using the IGS post-processed precise orbit and clock as references.Results show that the bias of BeiDou broadcast ephemeris can reach up to 2 meter.To further verify this finding, we perform precise point positioning for about 18 MGEX stations using BeiDou broadcast ephemeris and wide-area differential correction parameters.Data of 97 days are analyzed and pseudo-range residuals of each frequency for each station are derived.Systematic biases are found in the residuals using broadcast ephemeris.Comparing the BEB applying the differential correction parameters with the TGD difference between IGS and BeiDou broadcast ephemeris, we find that the correlation coefficient of TGD differences and BEB values could reach up to 0.89.This proves that the BEB applying the differential correction parameters is mainly due to the biases of the TGD parameters in broadcast ephemeris.By correcting the biases into TGD parameters, we performed point positioning at different stations.Results show that after applying the biases, the pseudo-range error reduces much, and the positioning precision can improve about 14.9%, 28.4%, 15.5% in N,E,U, direction for dual-frequency users, respectively.