GNSS height conversion method based on ultra-high order earth gravitational model

To make the ellipsoidal height obtained by Global Navigation Satellite System (GNSS) directly applied to engineering construction, it was necessary to convert the ellipsoidal height to normal height. This paper researched the GNSS height conversion method based on 5 ultra-high-order earth gravity field models combined with the improved “removal fitting recovery method”. The comparative analysis of the experimental results showed that in the experimental survey area, the height anomaly directly calculated by SGG-UGM-2 earth gravity field model was more consistent with the real height anomaly, and the mean square error was ± 0.009 3 m. When the “removal fitting recovery method” was adopted, the fitting effect of the height anomaly using XGM2019e_2159 earth gravity field model was better, and the mean square error, range, skewness value, and kurtosis value were the smallest, which were ±4.786 6 mm, 18.8757 mm, −0.648 8 and 0.887 8.