The baseline surveys in the Grosses Moos between Walperswil and Sugiez
Cartographica Helvetica 34 (2006) 3–15
A prerequisite for surveying a country is an area-wide, triangular network called a triangulation. In order to calculate the first triangle, at least one of the sides (baseline) as well as the two adjacent angles must be known. In view of surveying the entire Swiss territory, a 13 km baseline was measured in 1791 by Johann Georg Tralles and Ferdinand Rudolf Hassler in the "Grosses Moos" between Walperswil and Sugiez using a 32.5 m Ramsden measuring chain. The two scientists measured this baseline a second time in 1797 with 7.8 m iron rods. For the first official topographic map, the Topographische Karte der Schweiz 1:100,000, Guillaume-Henri Dufour had the measurements repeated in 1834. Astronomer Johannes Eschmann used 5.8 m iron tubes.
The two end markers of the baseline were renovated in 2006. In addition, a wooden pyramid was erected as a monument over the marker in Walperswil. On this occasion, the two markers were observed using GPS, and the distance was calculated from the measured coordinates. These four results agree within 19 cm (represents 0.0145 ‰) and are thus a further testimony to the outstanding Swiss precision.