History of Surveying and Measurement

Figure of the Earth

By the figure of the earth is meant the set of parameters that define the size and shape of the earth. In its simplest form if considered as a true sphere that would be the radius. As the accepted figure is more complicated than that so there are more parameters. Included in this is also the range of methods and equipment that over the years have been used to determine the parameters.

Among these methods are arc measurements and the use of baselines in triangulation schemes. In addition particular personalities have played important roles in the gradual refining of the results.

A listing and details of the methods used is being accumulated. From the earliest measures such as that attributed to Eratosthenes c230 BC to the numerous ones made since the introduction of triangulation by Snellius and others in the early 17th century up to the introduction of electromagnetic methods from the early 1950s.

Among the useful references are:

Erdgestalt, Kosmologie und Weltanschauung. V Bialas. 1982. Konrad Wittwer, Stuttgart. ISBN 3-87919-135-2

Ellipsoidischeparameter der Erdfigur (1800-1950). G Strasser. 1957. Deutsche Geodätische Kommission. München.

From Plane to Spheroid. Determining the figure of the Earth from 3000 BC to the 18th century Lapland and Peruvian survey expeditions. J R Smith. 1986. Landmark Enterprises, California. ISBN 0-910845-29-8

The History of the theories of attraction and the Figure of the Earth. 2 vol. I Todhunter. 1873. Macmillan and Co.

Practical geodesy. M Hooijberg. 1997. Springer-Verlag, Berlin. ISBN 3-540-61826-0

Figure of the Earth. G B Airy. 1845. Encyclopaedia Metropolitana. Vol. 5 pp 165-240

Introduction to geodesy. The history and concepts of modern geodesy. J R Smith 1996. John Wiley & Sons. ISBN 0-471-16660-X

From Geometrei. J Kobel, 1556. Courtesy Jan de Graeve.