In order to be able to depict a building, a municipal border or the edge of a road in a plan, points have to be measured and their coordinates have to be calculated. Several methods and processes are available for this purpose, and the most frequently used are:

The oldest surveying method is terrestrial imaging, i.e. surveying from the ground. The most commonly used instrument for this purpose is the tachymeter, which measures angles and distances, and uses these to calculate the coordinates and height of the objects to be surveyed. The digital models in use today carry out these calculations directly. The data are stored in the device and can subsequently be transferred to the computer system in the office for further processing.

This is a well-established and extremely accurate method of calculating height differences. The levelling device is set up between two upright poles, the target line of which is aligned horizontally. The variation between the two readings on the upright poles corresponds to the height difference.

Positioning with the aid of satellites (GNSS) is also used in cadastral surveying. Navigation satellites orbit our planet and constantly transmit signals to the ground, where they are registered using special receivers. Distances can be measured with the aid of these signals and the position of the recipient can thus be calculated. Through the application of special measurement and evaluation methods, or the use of reference data from Switzerland’s automatic GNSS network (AGNES), it is possible to calculate coordinates and heights extremely accurately (to within a few centimetres) in just a few seconds.

With the aid of photogrammetry the terrain is systematically flown over and photographed from the air. A special digital surveying camera is used for photographing from a manned aircraft or a drone. With the aid of special computer systems or evaluation devices, the images are subsequently merged to form a single picture so that the surface appears three-dimensional (stereo effect): mountains tower up before our eyes, and ravines appear to gape open. Objects can thus be recorded in three dimensions and contours can be evaluated.

For surveying purposes, laser scanning is carried out from the air. A laser device installed in an aircraft scans the terrain below. The distance from the ground can be calculated on the basis of the position of the aircraft and the duration of the signal, and this makes it possible to obtain information regarding the topography and structure of the terrain.