Strategies for Solving the Vertical Datum Problem Using Terrestrial and Satellite Geodetic Data

Abstract

The classical procedure of establishing precise height networks is based upon geodetic levelling, potentially including gravity information along the levelling lines. Since levelling is a relative operation some vertical datum must be fixed in order to determine “absolute” heights of benchmarks. In most cases the vertical datum of a height network has been defined by assigning zero height to the long-term mean value of local sea level observed at a fundamental tide gauge station. The vertical datum of largely extended height networks has often been fixed by employing several tide gauge stations situated along the coastline. In any case the definition of datum of classical vertical networks is connected with the concept of local mean sea level; the equipotential surface of the earth’s gravity field passing through the fundamental tide gauge mark is the reference surface of heights derived from levelling.