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Summary

Fortification maps: Secret military maps of Switzerland 1888–1952

Fortification maps and cartography have been inseparably linked since the early modern period. Already in 1588, the architect in charge of renovating the city walls of Basel demanded that the existing ramparts had first to be surveyed and shown on a map. However, during the following centuries, fortification maps were limited to the immediate surroundings of the structures. They were not uniform and varied from canton to canton.

The fortification maps discussed here came into existence simultaneously to the development of military structures and fortifications in Switzerland. In response to the inauguration of the Gotthard Railway, the Federal Council decided in 1885 to fortify the southern front of the Gotthard. The artillery fort «Fondo del Bosco» to the west of Airolo was to secure the south portal and thus constituted the core of the Gotthard fortification, reaching from Andermatt to the Oberalp, Furka and Grimsel passes. Because there was no direct line of sight from the cannons stationed at the forts to most of the anticipated targets, indirect firing methods had to be developed. This required the accurate definition of the geometric configuration between cannon and target with the help of precise maps. Thanks to these, it was possible to calculate the appropriate elements for aiming the cannons at a particular target. The Topographic Atlas of Switzerland 1:50 000 (aka «Siegfried Maps») proved insufficient and thus the scale 1:10 000 was chosen for the majority of fortification maps.

The fortified area around St-Maurice started being mapped in 1891 whereas the region of Monte Ceneri was begun only shortly before World War I. The Chief of Armaments and the Engineering Corps, who also directed the Engineering Bureau, the Fortification Bureau and the Topographic Bureau, coordinated the work of up to 150 topographers for the original surveys for the fortification maps. The method of the plane table was used for surveying but after 1892, experiments using terrestrial photogrammetry (using photographs) were carried out in three regions. Because of insufficient evaluation methods, it was not possible to apply this procedure for production. It was only during the First World War that the «surveying detachment St. Gotthard» was able to increase cartographic production thanks to the development of efficient instruments for stereo photogrammetry.

At the beginning of the Second World War, the fourth large fortification map series was surveyed in the area of Sargans. It was realized directly together with the elaboration of the General Plan of the Swiss Cadastral Survey, based on the Swiss Civil Code which was introduced in 1912. The surveying priorities between the civil and military authorities were coordinated in such a manner as to deem a purely military survey unnecessary. In around half a dozen so-called «border surveys», the foreign territory to be mapped was clearly larger than that of Switzerland. In addition to available foreign maps, aerial photographs taken by the Federal Office of Topography a few weeks before the war broke out, were also used for the surveys.

At the beginning of the 1950s the artillery service at the Federal Office of Topography was closed due to financial cutbacks, and the production of fortification maps which at that time covered approx. 7.5% of the area of Switzerland was discontinued. Hence, this special period of the history of Swiss cartography lasted around 65 years. This cartographic material classified as secret was of excellent quality and was not declassified until 2009.

Translation by Christine Studer

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