基于双频GPS观测的电离层TEC与硬件延迟反演方法

利用全球定位系统（Global Positioning System，GPS）的双频观测数据反演得到电离层的总电子含量（Total Electron Content，TEC），使得广域甚至全球范围高时空分辨率的电离层观测研究成为可能，但由于GPS卫星和接收机对信号的硬件延迟可导致TEC测量系统偏差，因此，需要探索反演TEC并估测GPS卫星与接收机硬件延迟的有效算法.本文根据电离层电波传播理论，阐述了基于双频GPS观测提取电离层TEC的方法，给出TEC与硬件延迟的基本关系.综合研究了TEC与硬件延迟的反演方法，进行分析与归纳分类，在此基础上提出了有待深入研究的问题. 

Derivation of TEC and GPS hardware delay based on dual-frequency GPS observations

The ground-based GPS receivers and hence networks enable studies of the ionosphere on a large regional or global scale by measuring the ionospheric TEC from dual-frequency GPS observations. However, originated in the hardware delay of the GPS satellite and receivers, a systematic bias affects the accuracy of the TEC derivation greatly. For accurate estimation of TEC, satellite and receiver instrumental biases should be removed from TEC measurements properly. This paper gives a comprehensive review of the algorithms on TEC and GPS hardware delays derivations. Starting from ionospheric radio wave propagation, the paper describes how the TEC is related with hardware delays. Then the TEC derivation methods are analyzed, evaluated and categorized into 3 main types. Finally, some suggestions are provided for further research on derivation of TEC and hardware delay.