National Land Survey of Sweden - SWEN 01L, a new Swedish Geoid

SWEN 01L -
a Swedish Geoid Model

SWEN 01L is a new national geoid model provided by the National Land Survey of Sweden.
(It replaces the previous model SWEN 98L).

SWEN 01L is based on a Nordic geoid model, NKG 96, which was computed by a working group of the Nordic Geodetic Commission (NKG), supervised by Rene Forsberg at the Danish KMS (Kort og Matrikelstyrelsen) in Copenhagen. NKG 96 in its turn is based on the global geoid model EGM96 combined with high-resolution gravity data and height data over the Nordic area.

Being a Nordic geoid model, NKG 96 is not adapted to the Swedish height system, RH 70, and the Swedish reference system for GPS, SWEREF 99. The model has therefore been fitted to these Swedish systems. Doing so, it has been necessary to take into account the post-glacial land uplift between 1970.0, the epoch of RH 70, and 1999.5, the epoch of SWEREF 99. The adapted model is denoted SWEN 01L, where the letter L indicates that the effect of post-glacial land uplift is taken into consideration.

How to use SWEN 01L
A grid of height corrections covering the area 55°N to 70°N in latitude and 10°E to 25°E in longitude represents SWEN 01L. The spacing of the grid is 0.025° in latitude, and 0.050° in longitude. In total, the grid consists of 601 rows, each holding 301 correction values. The height correction for any point is computed by bilinear interpolation between four neighbouring points of the grid. The grid positions are supposed to be given in SWEREF 99.

A package composed of the grid file, a program library (DLL) and a simple test program is available on the Web, as a downloadable zipped self-extracting file, named Geoidpak.
The documentation is written in Swedish, however a brief description in English is included.

Worked example: Given a point measured by GPS, with position latitude 60° 06' 39", longitude 16° 05' 32" and height above ellipsoid 177.538 m. All values expressed relative the GRS 80 ellipsoid in SWEREF 99. Interpolation in the SWEN 01L grid gives a height correction of 27.400 m. The levelled height of RH 70 becomes 177.538 - 27.400 = 150.138 m.

Fig. 2 Geoid undulations of SWEN 01L. Map from SGU (Sven Aaro)

If you have any questions concerning SWEN 01L, please contact:

Mikael Lilje
Lantmäteriverket
SE-801 82 Gävle
Tel: +46 26 63 37 42
E-mail: [email protected]

SWEN 01L, Geoid Online

Enter latitude and longitude (deg min sec)
in SWEREF 99 (global system WGS 84)
and click OK