From a Regional Project to an International Organization: The “Baeyer-Helmert-Era” of the International Association of Geodesy 1862–1916

Abstract

The following paper describes the first epoch of organized international collaboration in geodesy, which started about 150 years ago and finally led to today’s “International Association of Geodesy”. This development may be regarded as a consequence of the refined definition of the figure of the Earth, originating at the end of the seventeenth century and leading from the rotational ellipsoid to the equipotential surfaces of the gravity field, close to mean sea level. An increasing number of geodetic enterprises based on astronomic, geodetic and gravimetric measurements followed until the middle of the nineteenth century, in order to determine the curvature of the Earth’s figure at different regions of the world. The arc measurement based on triangulation played a special role at these endeavours, because this method was now increasingly used as the basis for national mapping. In 1861, the retired Prussian General Johann Jacob Baeyer took up earlier ideas from Schumacher, Gauss, Bessel, Struve and others, and proposed an arc measurement project for central Europe in order to systematically study the figure of the Earth in this region. The proposed network ranged from southern Italy to Norway, and from France to Poland, and its survey and evaluation naturally required international cooperation. Baeyer’s initiative immediately got the support from the Prussian government, and the enthusiastic collaboration of the European countries soon reached far beyond the original project. Consequently, the name of this “governmental” scientific organization changed from “Mitteleuropäische Gradmessung” to “Europäische Gradmessung”, and the scientific program widened significantly by including levelling, mean sea level investigations, standardization of length and time measures, and gravity observations. Baeyer remained the dominating person of the “European Arc Measurement” until his death (1885), keeping a strong position as the President of the Association’s Central Bureau hosted at the newly established Prussian Geodetic Institute. The following epoch is governed by Friedrich Robert Helmert, well-known by a fundamental monograph on “Higher Geodesy”, who became appointed Director of the Geodetic Institute and the Central Bureau in 1886. The regional organization immediately extended to the global “Internationale Erdmessung” (“Association Géodésique Internationale”), and the scientific program was enlarged significantly, with strong accent on physical geodesy and geophysics including investigations on temporal variations. This epoch ended due to the First World War, when the governmental convention on the Association was not extended. Although a reduced association among neutral nations succeeded in keeping the Latitude Service alive, the next era of international cooperation in geodesy only followed in 1922, within the frame of the non-governmental “International Union of Geodesy and Geophysics”.