Development of a local quasigeoid model for Vietnam land area using the global EGM2008 model

The article presents the results of research on the development of methods for obtaining normal heights in Vietnam using the global geoid model EGM2008 and software for processing GNSS measurements. The errors between the normal heights computed by the global model of the EGM2008 geoid and the heights found by GNSS measurements and geometric levelling on the territory of Vietnam are determined. The localisation method for the global geoid model EGM2008 for Vietnam's territory is suggested, such a geoid model is practically formed as the EGM2008_ TN file. Tests of the developed technique and the localised model of the EGM2008__TN geoid were carried out, showing the possibility of its application to obtain normal heights from GNSS measurements in Vietnam with the 4th levelling accuracy class.