From Sphere to Geoid - The Earth and Space Technology

Detrekoi, Akos

The earliest written document on the theoretical shape of the Earth comes from Homer where the Earth was viewed as a flat disc surrounded by oceans. A few centuries later the Greeks viewed it as a sphere, which was supported by various observations and even the radius of a spherical Earth was calculated. The discoveries of the great astronomers of the 16th and 17^th century showed that the shape of the Earth could not be a sphere. Based on their calculations they viewed it as a rotation ellipsoid. By the second half of the 19^th century we came to understand that the rotation ellipsoid as a theoretical earth shape is not sustainable in all cases.
Today we acquire more precise information on the geoids with the help of satellites, especially with those serving navigational purposes. With the help of remote sensors we can learn about the surface of the earth without actually having to come into contact with it. The lecture reviews in detail the traditional and modern techniques used to explore the surface of the earth, particularly that of remote sensors. Through examples it demonstrates how much of our information on the Earth was obtained and reveals the opportunities that lie ahead.

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