A New Method of Ionospheric Grid Correction Based on Improved Kriging

摘要

Ionospheric delay is one of the main sources of GNSS positioning error. The single frequency user of WAAS calculates ionospheric delay corresponding to the satellite in sight as well as confidence bound with grid ionospheric correction. Currently, Kriging algorithm is adopted in WAAS to estimate GIVD and GIVE. However, only spatial correlation of samples is considered in conventional Kriging. And just IPP delays in current moment are applied in the algorithm. Since the limited IPP measurements information, the uncertainty of the estimated GIVD is high, that is the estimated GIVE is conservative. Under the condition of meeting the requirement of integrity, an accurate estimation of the uncertainty of GIVD to decrease the GIVE can increase the service availability of system. Therefore, this paper proposes an Improved Kriging algorithm which can provide more reasonable GIVE. The temporal and spatial correlations of IPP delays are considered, and IPP delays during update period are applied in the new algorithm. The simulation is made using ionospheric data collected from WAAS reference stations in this paper. Firstly, we analyze the estimation accuracy of the two Kriging algorithms. Then, we evaluate the estimation performances of the two Kriging algorithms. Finally, we use the two Kriging algorithms to correct user IPP delay with grid ionospheric correction. The results show that the two Kriging algorithms have basically the same ionospheric delay correction accuracy. And the GIVE provided by Improved Kriging is smaller. Consequently, the UIVE from Improved Kriging can bound the ionospheric delay correction error more tightly.