Cross disc
A cross disk is a geodesy instrument for setting out right angles . It consists of a conical metal body, 10 cm high, 14 cm at the largest diameter, with cross-shaped target slots. It is screwed onto a stable metal rod and has a circular level to control the vertical position. The Oldham used for construction of solder by being used on a known base point, and through the slots, the flight bars instructor. This makes it particularly suitable for staking out, and its stable construction and robust handling have proven very useful. A sight is possible via the opposite target slots . The advantage is that you can aim at an angle, i.e. uphill or downhill, through its target slots. It is therefore used a lot in hilly terrain (e.g. southern Germany). Setting out right angles up to 40 m. The accuracy is ± 2 cm at 30 m. The cross disc has been in use at least since the Württemberg state survey .
The cross disk
The cross disk
The Roman groma was a forerunner of the cross disk that worked on the same principle .
Today the cross line laser is used.
Individual evidence
Web links
Introduction to measurement technology at uni-siegen.de (PDF; 174 kB)