Status and development of the European height systems

After a break of ten years, the work on the United European Levelling Network (UELN) resumed in 1994 under the name UELN-95. The objectives of the LJELN-95 project are to establish an unified vertical datum for Europe at the one decimeter level with the simultaneous enlargement of UELN as far as possible to include Central and Eastern European countries. More than 3000 nodal points were adjusted linked to the reference point of LTELN-73 (gauge Amsterdam). The new heights in the system UELN-95/98 are available for more than 20 participating countries.The European Vertical Reference Network (EUVN) is designed to contribute to the UELN project along with the connection of European tide gauge benchmarks as contribution to monitoring absolute sea level variations, the establishment of fiducial points for the European geoid determina­tion. The EUVN includes 196 points all over Europe. At every EUVN point, three-dimensional coordinates in ETRS89 and levelling heights pri­marily in the system of the UELN-95 have to be derived. The GPS computations are finalised, some levelling connections still have to be realised. At the tide gauge stations of EUVN additional sea level observations have to be included.The height systems will be developed as a com­bination of GPS permanent observations, levelling, and geoid information under consideration of well known vertical movements towards an European kinematic height reference system.