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Positioning service principle

GNSS positioning is based on measuring the distances between positioning satellites and user receiver. When the distances to several satellites are measured, the user receiver position can be computed by using the known positions of the satellites.

The distance measurement and its reliability is affected by several error sources. The accuracy of the user position can be improved by defining the effect of the error sources on the distance measurements by using GNSS reference stations at known positions. The modelled size of the errors is sent to the user of a positioning service as corrections. The user receiver can use the corrections to improve the positioning accuracy.

Observation data from all FinnRef stations is sent in real time to the NLS processing center, where the error modelling takes place using GNSMART positioning service software. Error sources affecting GNSS measurements are modelled, such as ionospheric and tropospheric error, and errors in the satellite positions.

The error model is used to generate real-time correction data streams. The users of NLS positioning service can access these streams with their receiver to improve the positioning performance.