基于非组合精密单点定位的区域电离层建模

Regional Ionosphere Modeling Based on Non-combined Precise Point Positioning

电离层是地球空间的重要组成部分,电离层延迟是全球导航卫星系统(global navigation satellite system,GNSS)数据处理的重要误差源,电离层的影响主要表现为地面站接收到的卫星载波和伪距信号的附加时延效应,最大可达几十米,精确的电离层模型可以有效提高GNSS单频数据处理的精度。利用GNSS观测值研究电离层,一般采用无几何距离组合的码和相位观测值,使用相位平滑伪距方法得到平滑电离层观测值,但是该方法容易受到伪距多路径和观测噪声的影响,导致电离层估计不准确。因此,先基于非组合精密单点定位(precise point positioning,PPP)提取电离层,利用国际GNSS服务的轨道、钟差等产品,有效减少待估参数个数,提高电离层延迟的估计精度;再使用纬度差和太阳时角差的多项式拟合进行区域电离层建模。利用某省连续运行参考站系统数据提取了天顶方向总电子含量信息进行建模,与PPP解算结果进行比较,在测站天顶方向上的模型值和解算值差异较小(除个别卫星外),可达到2 TECU左右。

The ionosphere is an important part of the earthspace.Ionospheric delay is one of the important error sources for GNSS data processing. The influence of ionosphere is mainly the additional delay effect of satellite carrier and pseudo range signal received by ground station,maximum up to tens of meters. The accurate and effective ionospheric model can effectively improve the accuracy of GNSS single frequency data processing. Using GNSS observations to study the ionosphere,the code and phase observation values of geometry-free(GF, geometric distance) are generally used. However, this method is vulnerable to pseudo range, multipath and observation noise, which leads to inaccurate ionospheric estimation. Therefore, this paper is based on the method of extracting ionosphere from non combination PPP. By using the products of IGS orbit and clock difference, the number of parameters to be estimated is effectively reduced, and the estimation accuracy of ionospheric delay is improved. Then, the regional ionosphere model is modeled by polynomial fitting of latitude difference and solar time angle difference. Extraction of ionospheric VETC information is then modeled by a CORS data, and the results are compared with those of PPP. When the station can receive the model value that the satellite reaches the maximum altitude angle, the difference of the calculation value is small(except for some satellites), and it can reach about 2 TECU.