Evaluation of normal heights by the means of global navigation satellite systems and global geopotential model

This paper presents geometrically and physically defined height systems, along with their evaluation by the means of Global Navigation Satellite Systems (GNSS) and Global Geopotential Models (GGM). The paper defines ellipsoid heights as an instance of geometrically defined heights; with physically defined heights being represented by definitions of orthometric and normal heights. Methods of normal heights calculation by the means of ellipsoid heights are presented in detail, as determined using the GNSS and height anomalies calculated from the GGM application. Apart from the above, numerical part of the paper evaluates normal height values and compares them to their conditionally accurate values at 1073 points with relatively uniform distribution over the entire territory of Serbia. Conditionally accurate values had been determined by the means of classical geodetic terrestrial methods. Under the procedure of evaluating normal height values, GGM - GGM05C was used, as created in 2016 by the Center for Space Research, University of Texas at Austin. In order to evaluate the quality of applying the model above, data on normal heights evaluation were also presented, using the GGM EGM96, created in 1996 by the National Imagery and Mapping Agency (NIMA), Goddard Space Flight Center (GSFC - NASA) and Ohio State University, presently being the most commonly used model. The comparison above indicates that application of the GGM05C model provides 50 % greater quality of normal heights evaluations against the ones obtained using the EGM96 model.