ED50

ED50 ('European Datum 1950') is a geodetic datum which was defined after World War II for the international connection of geodetic networks. ED50 ('European Datum 1950') is a geodetic datum which was defined after World War II for the international connection of geodetic networks. Some of the important battles of World War II were fought on the borders of Germany, the Netherlands, Belgium and France, and the mapping of these countries had incompatible latitude and longitude positioning. This led to the setting up of ED50 as a consistent mapping datum for much of Western Europe. It was, and still is, used in much of Western Europe apart from Great Britain, Ireland, Sweden and Switzerland, which have their own datums. It used the International Ellipsoid of 1924 ('Hayford-Ellipsoid' of 1909) (radius of the Earth's equator 6378.388 km, flattening 1/297, both exact). That spheroid was an early attempt to model the whole Earth and was widely used around the world until the 1980s when GRS 80 and WGS 84 were established. Many national coordinate systems of Gauss–Krüger are defined by ED50 and oriented by means of geodetic astronomy. Up to now it has been used in databases of gravity fields, cadastre, small surveying networks in Europe and America, and by some developing countries with no modern baselines. ED50 was also part of the fundamentals of the NATO coordinates (Gauss–Krüger and UTM) up to the 1980s. The geodetic datum of ED50 was centred at the Helmertturm on the Telegrafenberg in Potsdam, (then East) Germany; the intent was to encourage cooperation with the socialist states during the cold war, which failed. The adjustments for later versions of the datum (ED77, ED79) used the Munich Frauenkirche as starting point. The longitude and latitude lines on the two datums are the same in the Archangel region of north-west Russia. As one moves westwards across Europe, the longitude lines on ED50 gradually become further west than their WGS 84 equivalents, and are around 100 metres west in Spain and Portugal. Moving southwards, the latitude lines on ED50 gradually become further south than the WGS 84 lines, and are around 100 m south in the Mediterranean Sea.