The Median Method of Gross Error Elimination in Multi-satellite Precise Orbit Determination

The Multi-satellite Precise Orbit Determination (MPOD) is the most commonly used method in orbit determination of Global Satellite Navigation System (GNSS). In daily operation, malfunctions occur sometimes and gross errors appear in the observation of some monitoring station receivers. Too many gross errors during the orbit determination arc may cause the increasing number of orbit determination iterations or even the crash of MPOD program. In this study, the influence of receiver gross errors is studied, and the median method of gross error elimination is proposed, which makes use of the insensitivity of the median to gross error. The results show that in extreme cases when gross errors exist both in the observation of multiple receivers and satellites, they can also be eliminated very well, which ensures the normal operation of MPOD program and greatly improves the reliability and robustness of orbit determination operation. After a lot of tests, the median method has been successfully applied to online MPOD operation.