European date 1979

The ED79 of the geodetic European network is a particularly precise version of the ED50 (European Datum 1950) or the ED77 .

It is the last internationally balanced surveying network in Western and Central Europe, which is primarily based on terrestrial measurements. However, the influence of the vertical deviations on the measurements and the network geometry is precisely taken into account ( astro-geodetic network adjustment ); the stabilizing effect of Laplace azimuths was also used.

The revisions that have taken place since then and the most modern networks also combine the data from the individual state surveys , but (in contrast to the networks up to around 1980) also include the results of satellite geodesy . The importance of the latter increases in the long term because the large-scale accuracy of satellite methods (GPS, SLR, altimetry, etc.) is superior to ground-based measurements.

In the network versions of the ED50 and the ED77, the connecting seams of the individual national surveys are theoretically calculated correctly, but the data on the vertical deviations were still very incomplete until the 1970s .

Under the pioneering role of mountain countries such as Austria (K. Ledersteger, K. Litschauer) and later Switzerland and Scandinavia, as well as Germany (H. Sigl, W. Torge) and after publications about some test networks (Bavaria / Allgäu, Vienna, Hanover) recognized the importance of vertical deviations for increasing the accuracy of even large networks. The European surveying administrations agreed in a process that was, however, lengthy, on several revisions of the European network , which ultimately resulted in the ED77 version. Soon afterwards, the flatter countries of Western Europe also had sufficient vertical deviation data to start the revision to the ED79.

In Austria, which is particularly committed to astro-geodetic network adjustment , the accuracy in the first-order network increased by about a third due to the reduction in the vertical deviation, although the flat sights between mountain peaks of almost the same height remained almost unaffected.