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When using certain positioning services and GNSS calculations, you may need to perform coordinate transformations between ITRF / WGS 84 and SWEREF 99.
When is coordinate transformation between ITRF and SWEREF 99 required?
Positioning services based on Precise Point Positioning (PPP) give coordinates in the latest ITRF, current epoch, which can be said to be about the same as WGS 84. You can also obtain such coordinates when, for example, performing relative GNSS processing against stations in The IGS network (new window) .
The global reference system ITRS, International Terrestrial Reference System, is dynamic and includes a velocity model. The definition of SWEREF 99 means that Sweden's position on the globe is fixed to Europe's position in 1989, and that it is a static system in terms of geodynamic movements, such as plate tectonics and post-glacial land upplift. The difference between SWEREF 99 and WGS 84 is at present (2021) 7‑8 dm, increasing by a few centimetres per year.
Transformation ITRF2014 - SWEREF 99
When transforming coordinates between ITRF and SWEREF 99, the transformation between ITRF2014 and SWEREF 99 should be used in the first place, as it is the most up-to-date relationship.
If you need to transform between any other ITRF solution and SWEREF 99, the official ITRF transformations between the different solutions (new window) should be used for transformation to ITRF2014, and the transformation below to transform between ITRF2014 and SWEREF 99.
- Description of transformation between ITRF2014 and SWEREF 99 (pdf, new window)
- Grid files (model NKG_RF17vel) for interpolation of the internal deformations of the Eurasian plate in the Nordic countries (zip, new window)
This transformation is available in the PROJ transformation library (new window), version 7.2.1 and later. The transformation is also available through Lantmäteriet's own software for coordinate transformations, Gtrans, version 4.0 and later.
The transformation method is described in NKG2020 transformation: An updated transformation between dynamic and static reference frames in the Nordic and Baltic countries (new window).
Transformation ITRF2005 - SWEREF 99
This transformation is an older one, which you should only use if you have used the transformation before and need to continue using the same transformation to get consistent results.
- Description of transformation between ITRF2005 and SWEREF 99 (pdf, in Swedish, new window)
- Grid files (model NKG_RF03vel) for interpolation of the internal deformations of the Eurasian plate in the Nordic countries (zip, new window)
Simplified transformations
The simplified transformations are designed for situations where interpolation in the deformation grid cannot be handled. The transformations consist of annual parameters for a 7-parameter transformation. The expectation is that the need for this type of transformation will decrease now, when the general and accurate transformation between ITRF and SWEREF 99 is available in PROJ and Gtrans.
- Simplified transformations between ITRF2020/IGS20 and ETRS89 for maritime applications – for the period 2022-2026 (pdf, new window)
- Simplified transformations between ITRF2014 / IGS14 and ETRS89 for maritime applications - for the period 2015-2022 (pdf, new window)
- Simplified transformations between ITRF2008 / IGS08 and ETRS89 for maritime applications - for the period 2012-2015 (pdf, new window)
Questions and answers
Yes, PROJ supports transformation of Swedish national coordinate and height systems. See Swedish transformations in PROJ (pdf, in Swedish, new window) for a brief introduction to the most common transformations.