Construction of geoid and quasi-geoid height maps and their comparison on the territory of europe

The article describes the issue of reference surfaces used in height systems across European countries. Although the unified European Vertical Reference System EVRS2019 is currently adopted across Europe, many countries continue to use their national height systems actively. Among the most widely used types of height systems are orthometric and normal height systems. The reference surfaces for these systems are the geoid and the quasigeoid, respectively. Furthermore, national systems are often tied to different local mean sea levels, which vary from one another. Geoid heights are related to the deviation between the surfaces of the normal and the actual gravity potential at the ellipsoidal level, whereas quasi-geoid heights are related to the deviation between the surfaces of the normal and the actual gravity potential at the level of the Earth’s physical surface. From this follows the fact that the geoid and the quasi-geoid coincide over the seas and oceans, as the physical surface there coincides with the water surface of the World Ocean. Thus, these surfaces coincide over the oceans but differ over land. This difference over land is caused by the fact that with increasing elevation, the equipotential surface of the actual gravity potential becomes smoother and increasingly approaches the surface of the normal potential. This leads to an increasing difference between the geoid and the quasi-geoid as elevation increases. An important aspect is the ongoing improvement of the unified continental system and the establishment of transformation parameters between it and the national height systems of individual countries. This study presents maps of the geoid and quasigeoid heights across Europe. The differences between these surfaces have been calculated. The deviations of the geoid and quasigeoid surfaces are analyzed with respect to the elevation of the Earth’s physical surface. The aim of the article is to analyze the geoid and quasigeoid as reference surfaces for determining orthometric and normal heights, respectively. It also seeks to evaluate the quantitative characteristics of the deviations between these two surfaces across various European countries and to visualize the results in the form of illustrative maps. Keywords: geoid, quasigeoid, height system, orthometric height, normal height.