EPSG register for coordinate systems and transformations updated regarding Finnish systems

The National Land Survey of Finland (NLS) maintains national reference systems in Finland. Reference systems are often used by referring to a coordinate or height system using the EPSG register’s code. Transformations between systems can also be identified with EPSG codes. The NLS has now made a large number of updates in the EPSG register.

7.2.2025

The changes entered into force through register updates 11.024 (12 December 2024), 11.027 (6 January 2015) and 11.029 (21 January 2025) and can be used in geospatial data programs, among others, starting from these versions. In addition, the NLS has updated missing datasets in the PROJ transformation library. PROJ is broadly used in geospatial data software, including QGIS. After these updates, Finland’s all key national coordinate and height systems, as well as transformations between them, can be used in the EPSG register and PROJ.

Changes in the EPSG register

The register update included several changes that are listed generally below. Detailed changes and information about all EPSG codes used in Finland are available here. 

  • EUREF-FIN datum: The EUREF-FIN datum and related coordinate systems were added to the EPSG register. Previously, Finnish coordinate systems linked to EUREF-FIN had been linked to the European ETRS89 datum collection, which does not enable accurate transformations into national EUREF-FIN. As a result of the change, international datasets can be transformed into EUREF-FIN at the accuracy of cm. The change was made so that the EPSG codes of current plane coordinate systems (ETRS-TM35FIN, ETRS-GKn) linked to EUREF-FIN will remain unchanged. This aimed to minimise any consequences of the changes for users. However, it should be noted that the names of coordinate systems following the previous codes now start with EUREF-FIN in the EPSG register. This change in names only applies to the EPSG register, whereas the official Finnish names of plane coordinate systems have remained unchanged (e.g. ETRS-TM35FIN and ETRS-GKn).  
  • Height transformation planes (geoid models): EPSG codes have been registered for the Finnish height transformation planes FIN2023N2000, FIN2005N00 and FIN2000. The codes refer to transformations from ellipsoid heights to N2000 or N60 heights in EUREF-FIN.
  • KKJ <> EUREF-FIN transformation: a transformation (triangulated affine transformation, see JHS197) between the KKJ and EUREF-FIN systems based on the TINshift method (triangulated transformation) has been added to the EPSG register.
  • Transformations between height systems: transformations between height systems N2000 <> N60 and N60 <> N43 have been registered. These transformations are also based on the TINshift transformation (triangulated height transformation, see JHS163).
  • TM34, TM35 and TM36 zones: The plane coordinate systems EUREF-FIN / UTM34 zone 34N and EUREF-FIN / UTM36 zone 36N based on the EUREF-FIN datum and standardised UTM map projection system have been added to the register. For zone 35, the EUREF-FIN / TM35FIN code, to which another coverage area has been added in zone 35, can be used.
  • Compound coordinate systems: ETRS-TM35FIN+N2000 (E,N,H) has been registered as a new system, whereas only a combination was registered previously in which the sequence of the coordinate axles was N,E. Finnish maps and similar use the sequence E,N. In addition, EUREF-FIN (lat,lon) + N2000 height and EUREF-FIN (lat,lon) + N60 height have been registered as new combinations.
  • Minor updates have been made in the data of several registered codes. 

Changes in the PROJ transformation library 

These EPSG register changes will be updated in the PROJ transformation library version 9.6.0, which will be released on 1 March 2025. Changes shown in PROJ:

  • The TINshift transformations implemented in the EPSG register have now been implemented in PROJ using codes registered in EPSG. Previously, corresponding TINshift transformations had to be implemented internally in PROJ without using any EPSG codes.
  • The Finnish height transformation planes/geoid models FIN2023N2000, FIN2005N00 and FIN2000 have been added as new features in PROJ datasets.
  • Previous PROJ versions required the use of the area Finland parameter in addition to EPSG codes to achieve an accurate NKG2020 transformation. As a result of the update made in the EPSG register and the future PROJ update, this parameter will no longer be required, as the new EUREF-FIN codes determine the correct transformation directly. This update will probably be available in PROJ version 9.6.0 (March 2025). 

Significance of the changes for users    

The update enables the easy and standardised use of accurate and correct transformations, also reducing the probability of error. Through the EPSG register and PROJ, the open source transformation library, Finnish coordinate and height systems, as well as transformations between them, are now broadly available in standardised format. This improves the interoperability of datasets in applications that use the EPSG register and PROJ.

The registration of the EUREF-FIN datum enables unambiguous uses compared to the previously used ETRS89 datum collection. The addition of geoid models enables transformations of GNSS-based coordinates, including laser scanning point clouds, into the national height system.

All EPSG codes used in Finland and their explanations are available here. 

Further Information

Pasi Häkli, firstname.lastname@nls.fi
 

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