利用非组合精密单点定位技术确定斜向电离层总电子含量和站星差分码偏差

Calibration of Slant Total Electron Content and Satellite-receiver's Differential Code Biases with Uncombined Precise Point Positioning Technique

联合双频GPS数据,利用相位平滑伪距算法,可得到包含斜向电离层总电子含量(slant total electron content,sTEC)、测站和卫星差分码偏差(differential code bias,DCB)的电离层观测值(称之为"平滑伪距电离层观测值"),常应用于与电离层有关的研究。然而,平滑伪距电离层观测值易受平滑弧段长度和与测站有关的误差影响。提出一种新算法:利用非组合精密单点定位技术(precise point positioning,PPP)计算电离层观测值(称之为"PPP电离层观测值"),进而估计sTEC和站星DCB。基于短基线试验,先用一台接收机按上述两种方法估计sTEC,用于改正另一接收机观测值的电离层延迟以实施单频PPP,结果表明,利用PPP电离层观测值得到的sTEC精度较高,定位结果的可靠性较强。随后,选取全球分布的8个IGS(internationalGNSS service)连续跟踪站2009年1月内某四天的观测数据,利用上述两种电离层观测值计算所有卫星的DCB,并将计算结果与CODE发布的月平均值进行比较,其中,平滑伪距电离层观测值的卫星DCB估值与CODE(Centre for Orbit Deter mination in Europe)发布值的差别较大,部分卫星甚至可达0.2～0.3 ns,而PPP电离层观测值而言,绝大多数卫星对应的差异均在0.1 ns以内。

The ionospheric observables can be determined by combining dual-frequency observations of GPS through carrier-to-code leveling process,which mainly include the slant total electron content（sTEC）,satellite-receiver＇s differential code bias（DCB） and can be applied for ionosphere related research.However,the ＂leveled carrier phase ionospheric observable＂ is prone to be influenced by the arc length for leveling and receiver-dependent errors.In this contribution,an approach of calibrating sTEC and satellite-receiver＇s DCB with ionospheric observables estimated with uncombined precise point positioning（PPP） is proposed.With a short-baseline experiment,the sTEC determined with both kinds of ionospheric observations from one receiver were used to correct the corresponding observations of another receiver and single frequency PPP was implemented,the positioning results indicated a better reliability of sTEC calibrated with PPP-based ionospheric observables.Furthermore,by choosing a total of 4 days＇ observations from 8 global-distributed international GNSS service（IGS） tracking stations（i.e.4 days of Jan.2009）,all the satellites＇ DCB are solved and compared with the products published by Centre for Orbit Determination in Europe（CODE）,a discrepancy of no more than 0.1 ns can be found for PPP-based ionospheric observables in comparison of 0.2～0.3 ns for leveled carrier phase ionospheric observables,thus facilitate the precise study of ionosphere.