Bessel-Ellipsoid
The Bessel ellipsoid (also Bessel 1841) is a reference ellipsoid for Europe. Friedrich Wilhelm Bessel derived it from 1841 from the data of large-scale surveys in Europe, Russia, India and Peru.
The processed data of Bessel material comprises ten long meridian arcs and 38 precise measurements of latitude and partial length. Specifically, there are
- The French and English degree measurements,
- The Hanoverian, Prussian, Danish, Swedish and Russian degree measurement,
- Also those of the Paris Academy in South America ( Peru / Ecuador)
- And the two English East India profiles.
The total length of the measurement sheets of leather Steger is 50 ° 34 ', which corresponds to 5,700 kilometers considerable. Bessel edited the data material very carefully, so that he received a very good approximation to the currently known value for the earth's shape.
According to the then- computing technology, announced its results Bessel ( dimensions of the ellipsoid ) not only numerically in the then customary unit of length Toise, but also as logarithms. The defining parameters of the Bessel ellipsoid equatorial axis a and flattening f
Compared to the currently used Erdellipsoid, which is now known with decimeter, it has around 700 meters shorter axes a ( equatorial) and b ( polar). The exact values in comparison to other, such as the used for GPS surveying World Geodetic System WGS84 from 1984, can be found in this table.
Use
When published in 1841, the Bessel ellipsoid was the most accurate and was placed in the decades virtually all newer surveying networks based. Only with the ellipsoid of Clarke in 1880 and after the advent of geophysical methods of calculation ( including through Hayford 1920 ), some states went over to newer ellipsoids. But these are only regionally adapted the earth's curvature and therefore soft as well as Bessel's pioneering work of the world derived from satellite data ellipsoids of our Time.
The Bessel ellipsoid adapts its data base the geoid and the mean curvature of the earth in Eurasia particularly well and was therefore based on many national surveys, such as in Germany ( since 1989, again in East Germany ), in Austria, in Switzerland and in the Czech Republic and in the successor states of Yugoslavia. But also on other continents it is used, namely in Indonesia ( Sumatra, Kalimantan (Borneo ), Bangka Belitung ) and Japan ( Okinawa, Mean Solu ), also in Eritrea and Namibia.
In 1950, based about half of the triangulations in Europe and about 20% on other continents on the Bessel ellipsoid; strongly represented were the reference ellipsoid of Hayford 1908 ( " internat ell. in 1924 ," esp. for America and ED50 ) and Krassowski (especially eastern half of Europe).