Clarke ellipsoid

By Alexander Ross Clarke , an English surveyors , several were Between 1865 and 1880 earth ellipsoids calculated. Their exact values ​​in comparison to others, for example the Bessel ellipsoid from 1841, which was generally used in non-European areas until then , can be found in this table .

The Clarke ellipsoids are the basis of the national survey in many earlier British colonies to this day , although as early as 1910 it was shown by Friedrich Robert Helmert that the values ​​calculated by Clarke for the flattening of the earth are much too large. In these countries they are well adapted to the average curvature of the earth ; Globally, however, the curvature of the Clarke ellipsoids is too strong.

In general, the axes of such ellipsoids , determined from countless terrestrial measurements, do not only depend on the actual shape of the earth and the inevitable small measurement errors. The gravitational field also has a strong influence due to the so-called deviation from the perpendicular - and thus also the region from which the measurements originate.

Some of the ellipsoids determined since 1810, the first French degree measurement , therefore differ from one another by several hectometers or up to 0.01 percent. In relation to this, the Clarke ellipsoids agree relatively well with the modern equator axis .

Web links

• Countries with Clarke ellipsoid + some with Bessel, Hayford etc.