Helmert ellipsoid

The dimensions of the earth ellipsoid determined by Friedrich Robert Helmert in 1906 are:

Major semi-axis a = 6,378,200.0 meters; Earth flattening f = 1: 298.3

Helmert determined these values ​​on the basis of his potential theories from data that only covered part of the continents . Their accuracy was only achieved or exceeded by other scientists 50 years later (today's values ​​are 6,378,137 m and 1: 298.25) and prove his sense of geophysical influences on the earth's gravity field, which was far ahead of his time .

The geodesist and textbook author Karl Ledersteger , who died in 1970, considers two facts to be the reason for this doubted achievement (until 1924¹): on the one hand, the scientific intuition resulting from Helmert's extensive experience , on the other hand, the successful assessment of a disruptive influence on the topographical reduction of gravity data , which later became indirect Effect was called. In terms of the history of science, it would also be possible that Helmert's first thoughts on isostasis (mass balancing under the earth's crust ) played a role.

¹) Note: In 1924 the IUGG adopted the Hayford ellipsoid as the binding earth figure . A few years later than that determined by Helmert, it deviates significantly more from today's GRS80 with its parameters 6,378,388 m and 1: 297 .