A method for estimating GPS instrumental biases and its application in TEC calculation

In this paper the state equation and measurement equation of Kalman filtering for estimating GPS instrumental biases are presented. The method for calculating the initial value of the filter is also provided based on the calculation method of the relative instrumental biases of satellite and receiver. The GPS instrumental biases and the satellite instrumental biases relative to the mean is calculated, and the stability of the GPS instrumental biases and the satellite and receiver instrumental biases is evaluated. The results indicate that they are very stable during a period of two months and a half. Finally, the validity of the method is verified by the calculated results of TEC and the comparison between the calculated TEC and the estimated TEC.