Fork point

Pair of eyelets at a fork point in Vienna

Notice board of a fork point in Vienna

A fork point is a special marking of survey points for cities and other densely built-up areas. The measuring point is defined indirectly by two metal rods of equal length, which are hooked into two eyelets embedded in concrete on a building or a wall base . The two eyelets are concreted into the wall at the same height (approx. 20–40 cm) and protrude 2–3 cm. The fork is hooked into its approximately cm-wide holes so that it protrudes almost horizontally from the wall. For control purposes, the point is usually also marked as a ground point with a metal pen in the sidewalk .

The fork represents an isosceles triangle with an arm length between 1.3 meters and 2 meters. However, this length of the arms differs between individual cities. This type of marking is particularly widespread in Austria. In the point maps , not only the Gauß-Krüger coordinates of the fork point are given, but also those of the two metal eyelets.

The fork points are primarily used to mark switch-on points and are then attached at intervals of 300 to 500 meters. In Vienna alone , where they were introduced in the 1950s, there are several thousand of them.

They are relatively well protected due to their special position in the wall bases, but sometimes they are damaged or destroyed in the course of construction work. This must be reported to the land surveying office immediately. If this does not happen, it can be prosecuted according to the surveying law , as with other official markings of measuring points. More often, however, when replacing fence bases, the fork point is not reinserted, although appropriate warning signs are attached to the eyelets.

See also

• City surveying
• Traverse

Literature and web links

• R.Mansberger, A.Klisch: Measurement , chapter basic measurement . Lecture notes Univ. for soil culture, Vienna 2011
• Fork points to the multi-purpose map, city surveying Vienna
• Land Survey Systems , p. 8–11 in: BEV , 2011

Individual evidence

1. ^ Karl Kraus: Photogrammetry. Volume 2: Refined methods and applications, p. 268. Berlin 1996, ISBN 3110181630 , preview on Google books, directly to the side .
2. ↑ Christoph Twaroch: Law and Law , Österr.Zeitschrift für Vermessung 87, p. 155, Vienna 1999. Digitized on the website of the Department of Geodesy and Geoinformation of the TU Vienna , PDF 3 MB.