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Coordinate systems – WGS84, ETRS89 and projections
Why GNSS coordinates differ from cadastral ones: WGS84, ETRS89 and national projections, and how to set up the transformation in a controller or GIS.
5 min read
A GNSS receiver computes coordinates in a global (geocentric) reference frame. Maps, the cadastre and projects use national projections – which is why a transformation is needed.
- WGS84 – the global GPS system; most devices work in it "out of the box".
- ETRS89 – the European frame tied to the Eurasian plate; its offset from WGS84 is now several tens of centimetres and grows by ~2.5 cm per year due to continental drift.
- National systems in the region – the older Gauss-Krüger (Bessel 1841, zones 5/6/7) and newer ETRS89-based systems. Which one is official for your work is determined by the competent geodetic authority.
In practice
- Agriculture: it mostly doesn't matter – repeatability is what counts. Just don't mix AB lines recorded with different correction sources.
- Surveying and construction: in the controller, select the target coordinate system and transformation parameters (or a localisation on known points) in line with regulations.
- GIS and drones: set the output system (e.g. the projection's EPSG code) in your processing software before exporting.
Need the exact reference frame and base station position for your project? Write to us at info@rtk.ba.
Related: The difference between repeatability and absolute accuracy is explained in what RTK accuracy depends on, and controller setup in survey rovers and apps.