Abstract

In coordinate calculation from terrestrial measurements, the reduction due to the Earth's gravity field should be one of the main topics of consideration. The problem is of extreme importance especially in steep areas, where geoid surface is not parallel to the rotational ellipsoid. In this, the knowledge of the deflection of the vertical is significant. There are two ways for its acquisition: from the comparison of astronomic versus geodetic coordinates, or from the indirect way of calculation by using global, regional, or local geoid models. This paper reviews the deflection of the vertical and its use at the steep area under Krvavec. The computation followed from three models, EGM2008 and two Slovene models: the current SLOAGM2000 and the test model SLOAGM2010. In addition, the local geoid model was established from the ellipsoidal and the normal-orthometric heights. Significant differences in vertical deflection components originated from the EGM2008. We can confirm the expectation that in steep areas it is necessary to consider the geoid inclination. The best way to do this is the local geoid surface determination from the ellipsoidal in physical heights. In other cases, local geoid models are still appropriate. Contrary, we should avoid using global models because of their lower resolution.

Key words: Earth's gravity field, geoid, rotational ellipsoid, deflection of the vertical, terrestrial measurement reduction, Earth gravity field