Normal heights for GNSS reference station antennas

The GNSS reference station ellipsoidal heights are of the mm precision quality due to their continuous operation and monitoring of their coordinates in the international terrestrial reference frame. The GNSS reference station data is mostly used for rover positioning. The reference stations are very important also as a fitting points for the geoid modelling developments. Unfortunately, the importance of the referencing of antenna heights to the national levelling network are sometimes neglected. Usually the antennas are fixed on the roof of high buildings in urban environment. It is quite difficult to make a high precision levelling procedures and sometimes the direct geodetic measurements of antenna normal heights are not performed. Actually, for the most of Latvian GNSS reference network antennas the normal heights are not tied to the national levelling network. The aim of this research is to use the collected data of GNSS/levelling points for the determination of the normal heights of continuously operating reference station antennas.