Height systems and related sea level observations are based on a number of measurement systems, which all have their own characteristics and deliver different type of observations. Traditionally, sea level is observed at tide gauge stations, which usually also serve as height reference stations for national levelling networks and therefore define a height system of a country. Thus sea level research across countries is closely linked to height system unification and needs to be regarded jointly. In order to analyse all observations they need to be available in a common reference frame. Within this project three major objectives are addressed.
- Connection of tide gauge markers with the GNSS network geometrically by the geodetic SAR technique in order to determine the relative vertical motion and to correct the tide gauge readings.
- Determine a GOCE based high resolution geoid at tide gauge stations in order to deliver absolute heights of tide gauges with respect to a global equipotential surface as reference.
- Joint analysis of geometrical and physical reference frames to make them compatible, and to determine corrections to be applied for combined analysis of geometric and physical heights. These objectives are addressed by the project team with complementary expertise. The Baltic Sea serves as test area with very good geodetic infrastructure in order to identify the capabilities of the geodetic SAR technique for height system unification and determination of the absolute sea level at tide gauges.