With GNSS, it is possible to determine three-dimensional positions worldwide with an accuracy range of 5 to 10 metres using simultaneous measurements with 4 GNSS satellites. All that is required is a GNSS receiver, which is available on the market in various versions and with varying accuracy ranges, or is integrated into almost all mobile phones.

The GNSS signal passes through the earth's atmosphere on its way from the satellite to the receiver. Due to the weather, the atmosphere often has different properties in a small area. This changes the propagation time of the signal. By including stations with known coordinates, the so-called reference stations, these errors can be calculated out. The data used for this is therefore called correction data. Their use therefore increases the accuracy of the position measurement.

In the post-processing method, the measurements of the rover (a mobile GNSS receiver) are then adjusted so that, depending on the type of receiver, accuracies to within a few decimetres or centimetres can be attained. This differential method may also be carried out in real time. It requires a communication link (radio, mobile phone, etc.) between the reference station and the rover. Depending on the type of GNSS measurement (code or carrier phase), the method is referred to as differential GNSS (DGNSS) with accuracy in the metre range, or real-time kinematics (RTK) with accuracy in the centimetre range.

With its swipos product, swisstopo offers DGNSS and RTK positioning services for all of Switzerland, thus rendering the use of personal reference stations obsolete.