Observation procedures

Modern national surveying is based on the signals from GNSS navigation satellites (Global Navigation Satellite System) such as GPS.
The signals emitted by these satellites are received by receivers on the earth, and together with appropriate software, they can be used for highly precise positioning. In addition to being a very accurate and economic method, it has the advantage that a direct line of sight between points is no longer necessary.

Levelling is the classical and still valid method of determining heights.
The method is based on the linear addition of height differences from one point to another. These height differences are observed with a levelling instrument which is set up and adjusted exactly horizontally between two levelling rods. The difference of the two observations on the rods is the height difference between the two points.

This classical method of determining points is based on measuring directions, distances and vertical angles between neighboring points.
Ths instruments used for these observations are precise theodolites and distance meters. The computation and adjustment of these observations is based on the laws of trigonometry. This type of point determination is also called triangulation.