Optimization of GIVE algorithm for grid-based single shell ionospheric model over Chinese region based on residual statistics

To improve the service accuracy of the GNSS system and monitor the integrity of regional ionospheric activities, The BDSBAS system broadcasts the grid ionospheric correction parameters and GIVE to meet the precision approach needs. We use a planar fit algorithm to create an ionosphere map of the BDSBAS, in order to get a more accurate confidence bounds, we put forward a factor which is related to the Skewness and kurtosis of the residual distribution to control the decorrelation parameters to calculate the integrity parameter GIVE. The statistical results show that the ionospheric correction RMS of the BDSBAS grid-based single shell model is about 2~3 TECU, the correction percentage reaches 75%~79%; the GIVE envelope rate is better than 99.9%. Compared with the GPS basic navigation system, only adding the BDSBAS grid ionospheric correction can improve positioning accuracy by 20%~40%.