Ionospheric correction method for precise positioning with GPS active network

在长距离GPS实时动态定位(RTK)过程中,电离层延迟误差是影响定位精度的主要误差源。目前,由于采用全空间电离层模型精度不够,对长距离RTK定位主要采用双差电离层残差内插方式。本文提出一种新的电离层模型。该模型仅对每个卫星轨迹通过的电离层部分进行建模,可适用于高精度GPS定位。采用香港数据,结果表明,该模型可较好地模拟低纬度电离层变化,并可支持GPS厘米级定位精度。||The ionospheric delay error is a major error source which degrades the positioning accuracy in network real time kinematic (RTK) positioning over a long distance. Different approaches are proposed to estimate GPS errors based on GPS reference network, such as virtual reference stations (VRSs) and network corrections. A new method is used to model the ionospheric total electronic content (TEC) distribution in space. Unlike most ionospheric models, only the ionospheric delays along the satellite tracks are modelled. Therefore, the models are of high precise resolution of the ionospheric TEC distribution in both spatial and temporal scales. A new algorithm is used to solve the equation singularity problem. Experiments demonstrate that the new ionospheric correction method can be used to describe the ionospheric variation at a low latitude area where ionospheric activities are strong. Also, the accuracy of the ionospheric model is enough to support centimeter-level positioning within the network. As ionospheric models are satellite-based models (each satellite has one model), the model parameters can be easily incorporated with the existing differential GPS Radio Technical Commission for Maritime Service (DGPS RTCM) 104 format.