Determination of Orthometric Height using GNSS and EGM Data: a Scenario of the Federal University of Technology Akure

Authors : Herbert TATA, Raufu OLATUNJİ

Pages : 100-105

Doi:10.30897/ijegeo.754808

View : 8 | Download : 5

Publication Date : 2021-03-07

Article Type : Research Paper

Abstract :The advent of Global Navigation Satellite System insert ignore into journalissuearticles values(GNSS); and Earth Gravitational Model insert ignore into journalissuearticles values(EGM);particularly Global Positioning System insert ignore into journalissuearticles values(GPS); has modernized geodetic surveying in providing horizontal and vertical positions of points with a sub-meter level of accuracy over the reference ellipsoid. The GPS gives ellipsoidal heights which makes the conversion of the heights to orthometric heights possible by incorporating a geoid model. The conventional method of determining orthometric height is tedious, time-consuming, and labour intensive. This study entails the determination of orthometric height using GNSS and EGM data. A total of forty-nine insert ignore into journalissuearticles values(49); stations selected within the study area were occupied for GPS observation using South DGPS instrument in static mode for the position and ellipsoidal height determination. The geoidal height values of the GPS derived data were computed using GeoidEval utility software with reference to three different EGMs insert ignore into journalissuearticles values(EGM2008, EGM96 and EGM84);. In order to determine the orthometric heights of the selected stations, the difference between the EGM geoidal height values insert ignore into journalissuearticles values(NEGM); and the ellipsoidal heights were computed. The results show that the orthometric height obtained with respect to EGM2008 gives better results with a standard deviation of 9.530m and a standard error of 1.361m. The study reveals that the use of GNSS and EGM data for orthometric height determination is less expensive, less tedious, accurate and time-saving compared to the conventional approach of geodetic and spirit levelling.
Keywords : Orthometric height, GNSS, EGM, Geoidal height