SWEREF 99

SWEREF 99 stands for Swedish Reference Frame 1999 and is a realisation of the European reference system ETRS89.

The relation to WGS 84

WGS 84 and SWEREF 99 differ by 8–9 dm for the time being (2024); increasing with time as the European plate moves. Thus SWEREF 99, WGS 84 and the previous frame SWEREF 93 can be interchangeable for many applications.

Read more about the relation between SWEREF 99 and WGS 84.

Computation of SWEREF 99

SWEREF 99 is a realisation of ETRS89, performed in accordance with the EUREF guidelines, and was adopted as an improvement and extension of ETRS89 at the EUREF Symposium held in Tromsø, 22–24 June 2000.

SWEREF 99 was originally defined by the 21 original Swepos stations, the so-called fundamental stations. These are permanent stations  mounted on pillars on stable bedrock. The permanent stations Sweden (SWEPOS), Norway (SATREF), Finland (FinnRef) and Denmark, totally 49 stations, have been included in the SWEREF 99 solution. From Swepos, data for six GPS weeks 1014–1019, (June 13 – July 24 1999) were used and from the foreign stations, 2–3 weeks of data were used (GPS-weeks 1014–1015, 1019).

• The SWEREF 99 solution has been computed in ITRF97 epoch 1999.5 and then converted back to ETRS89 in accordance with the EUREF guidelines
• The epoch for plate tectonics is 1989.0
  The epoch for intraplate deformations is 1999.5
• The ellipsoid used with SWEREF 99 is GRS 1980

Review of SWEREF 99

The SWEREF 99 coordinates of the SWEPOS stations, that are defining the reference system SWEREF 99, were updated in the beginning of 2021. Since the original SWEREF 99 campaign, the coordinates of the SWEPOS stations have been updated when necessary, e.g. when antennas are changed and when new antenna models and computation strategies have been introduced. The purpose of the review and coordinate update is to achieve a more homogeneous SWEREF 99 that will be more sustainable for the future. An overall measure has been taken to obtain a reference system that is consistent with today's measurements and computations.

The number of defining stations has increased with the update, to some thirty stations in Sweden and, in addition, approximately 100 stations in our neighbouring countries. The number of foreign defining stations will however decrease with time, since we don't have the ambition to determine all foreign stations anew when they are altered.

The differences between the previous and the updated coordinates are, on the whole, small and lies within the specifications of the Swepos services.

Related information

• SWEREF 99 – an Updated EUREF Realisation for Sweden (pdf, new window), documentation from the EUREF symposium 2000.
• Plane coordinates in SWEREF 99 – SWEREF 99 TM and local projection zones
• Transformation between ITRF and SWEREF 99
• Transformation between RT 90 and SWEREF 99