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Information about both current and older Swedish geoid models can be found here.
Different geoid models
Several Swedish geoid models have been introduced over the years; see the list below. The reason why new models have been introduced, is the possibility to compute better and better models. This is partly because more observations have been successively collected and partly because the computation methods have been refined. As a rule, the most recent model published is the one to be used.
For a transformation between SWEREF 99 and RH 2000, the model SWEN17_RH2000 should now be applied. The model can be downloaded over the Internet; see the Geoid models page.
Briefly about the computation of SWEN17_RH2000
SWEN17_RH2000 has been computed by adapting the gravimetric geoid model NKG2015 to the Swedish reference systems by using a number of geometrically determined geoid heights. These are computed as the difference between heights above the ellipsoid determined by GNSS and the levelled heights above sea level. In this step, a correction has been applied for the postglacial land uplift together with a smooth residual surface used to model the GNSS/levelling residuals. The land uplift correction refers to half a year of land uplift, between the reference epoch of SWEREF 99, which is 1999.5, and the reference epoch of RH 2000, which is 2000.0.
The underlying gravimetric geoid model, NKG2015, has been computed under the umbrella of NKG, The Nordic Geodetic Commission, in a Nordic/Baltic cooperation.
The standard uncertainty of SWEN17_RH2000 has been estimated to 8‑10 mm everywhere on the Swedish mainland, Öland and Gotland with the exception of a few areas where the uncertainty is larger. These areas are to the far north on the border to Norway and in the lake Vättern (standard uncertainty approximately 2‑3 cm) and the highest mountains to the north-west, depending on the difficulties to model a gravimetric model in mountainous areas (standard uncertainty about 2‑4 cm). At sea, the standard uncertainty also larger; about 2‑4 cm in coastal waters and probably around 5‑10 cm further out.
- Presentation of SWEN17_RH2000 (pdf, in Swedish, new window)
- The difference between SWEN17_RH2000 and SWEN08_RH2000 (pdf; extract from the presentation above, in Swedish, new window)
SWEN17_RH70
SWEN17_RH70 is the corresponding model for conversion from SWEREF 99 to the older height system RH 70. Also this model can be downloaded from the Geoid models page.
The principle for the computation has been to first determine an optimal geoid model for the best Swedish height system for the time being, i.e. RH 2000. After that, an accurately determined system difference is utilised to determine the geoid model for the inferior height system RH 70. The two geoid models may thus be seen as one and the same model adapted to different height systems, which is also indicated by that the version number (year) 17 is the same for both models.
The standard uncertainty of SWEN17_RH70, close to the benchmarks of the national precise levelling network, is similar to the one of SWEN17_RH2000 on land, under the assumption that RH 70 is considered as realised by the RH 70 heights of stable benchmarks along the precision lines of the second precise levelling and the RHB 70 heights for the benchmarks of the third precise levelling.
Outline of Swedish geoid models
SWEN17_RH2000
The Swedish geoid model 2017; the Nordic geoid model NKG2015 adapted to SWEREF 99 and RH 2000. Includes corrections for the land uplift* and residual interpolation.
SWEN17_RH70
The Swedish geoid model 2017; the Nordic geoid model NKG2015 adapted to SWEREF 99 and RH 70. Includes corrections for the land uplift* and residual interpolation.
SWEN08_RH2000
The Swedish geoid model 2008; the Swedish model KTH08 adapted to SWEREF 99 and RH 2000. Includes corrections for the land uplift* and residual interpolation.
SWEN08_RH70
The Swedish geoid model 2008; the Swedish model KTH08 adapted to SWEREF 99 and RH 70. Includes corrections for the land uplift* and residual interpolation.
SWEN05_RH2000
The Swedish geoid model 2005; the Nordic model NKG2004 adapted to SWEREF 99 and RH 2000. Includes corrections for the land uplift* and residual interpolation.
SWEN 05LR
Former name of SWEN05_RH2000.
SWEN05_RH70
The Swedish geoid model 2005; the Nordic model NKG2004 adapted to SWEREF 99 and RH 70. Includes corrections for the land uplift* and residual interpolation.
SWEN 01
The Swedish geoid model 2005; the Nordic model NKG 96 adapted to SWEREF 99 and RH 70.
SWEN 01L
Version of SWEN 01 corrected for the land uplift*. Adapted to SWEREF 99 and RH 70.
SWEN 98
The Swedish geoid model 1998; the Nordic model NKG96 adapted to SWEREF 93 and RH 70. Predecessor of SWEN 01.
SWEN 98L
Version of SWEN 98 with correction for the land uplift*. Adapted to SWEREF 93 and RH 70.
RN 92
The Swedish geoid model 1992; transformed from the Nordic model NKG89.
RAK 70
Rikets Allmänna Kartverk 1970; older geoid model used for the computation of the third triangulation of Sweden.
* The postglacial land uplift correction is due to the reference systems not having the same reference epoch.
For the geoid models transforming between SWEREF 99 and RH 2000, the land uplift correction is half a year, to correct for the land uplift between the reference epoch of SWEREF 99 (1999.5) and the reference epoch of RH 2000 (2000.0).
According to the same principle, there is a correction of 29.5 years of land uplift correction built into the geoid models transforming between SWEREF 99 and RH 70. Thus, they correct for the land uplift between the epoch 1970.0, that is the reference epoch of RH 70, and the reference epoch of SWEREF 99 (1999.5).
Interactive computation of geoid height
Compute geoid height, using the SWEN17 models.