A COMPASS ionospheric delay grid correction algorithm for China

A new ionospheric delay grid correction algorithm combining the advantages of global fitting and local interpolation algorithms for COMPASS system is presented. Firstly, COMPASS ionospheric vertical total electron content error analysis are made to get the main error influencing factors and the corresponding impacts, including the factors of COMPASS timing group delay parameter accuracy, receiver inter-frequency bias parameter accuracy, projection function of different types, pseudorange multipath error and random noise. Secondly, an effective measurement combination of COMPASS B1 and B2 common frequencies is selected, to eliminate the larger multipath error from GEO satellites geostationary features and improve VETC accuracy. Thirdly, an ionospheric delay grid correction algorithm is proposed to combine traditional global fitting and local interpolation algorithms, ensuring a suitable solvability and accuracy of ionospheric delay to grid points. Finally, the algorithm is validated using COMPASS measurement data. The results demonstrate that the average ionospheric delay grid correction accuracy is better than 0.5 meter throughout the day.