Complete text (abstract only):
Until 1800, there existed only rough maps in the dukedoms Gotha-Altenburg and Weimar based on a net of geographical positions measured by simple instruments. After Franz Xaver von Zach had made his first astronomical observations to determine geographical coordinates he realised that these old maps had an accuracy of at best some minutes of arc.
The king of Prussia, Friedrich Wilhelm III (1797-1840), asked Zach in October 1802 to accept the direction of the measurement of the territories around Erfurt and the Eichsfeld. In this situation it was obvious for Zach to consider a survey of Thuringia and a great measurement of degree similar to the French model. His ideas were promoted by the duke of Sachsen-Gotha-Altenburg Ernst II (1772-1804). Zach planned to perform his survey in four degrees of latitude and six degrees of longitude with respect to the Seeberg observatory. The measurements had to cross over the borderlines of several countries.
The documents in the Forschungs- and Landesbibliothek prove that the diplomatic preparations for the survey got on until the end of 1803. Zach obtained passports and grants to pass and to survey some territories (Hessen-Kassel, Hannover, Coburg-Saalfeld, Braunschweig, Sachsen). Their governments had exchanged diplomatic notes on this topic.
The death of Ernst II in 1804, the consequences of the war (battle of Jena and Auerstedt in 1806) and Zach's resignation as director of the Seeberg observatory led to the end of the survey.
Forschungs- und Landesbibliothek Gotha: Chart A 2086 (1), Chart A 1274 (from page 162)
Zach, F. X. von: Nachrichten von der Aufnahme von Thüringen und dem Eichsfelde, Gotha 1806
Cornelia Hopf, Oliver Schwarz: Geodetic documents in the Gotha library. In: Peter Brosche, Wolfgang R. Dick, Oliver Schwarz, Roland Wielen (Eds.): The Message of the Angles - Astrometry from 1798 to 1998. Proceedings of the International Spring Meeting of the Astronomische Gesellschaft, Gotha, May 11-15, 1998. (Acta Historica Astronomiae ; 3). Thun ; Frankfurt am Main : Deutsch, 1998, p. 91.
Html-Version: Wolfgang R. Dick. Created: 21 Jan 1999