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There are close relationships between Swedish and international height systems.
IHRS and IHRF
The International Height Reference System IHRS is a reference system with a common global reference surface. The definition of IHRS was adopted by the International Geodesy Association (IAG) in 2015. The calculations of height systems are called realisations and will be referred to as IHRF, International Height Reference Frame.
Unlike traditional height systems, IHRS and IHRF are based on position determination with GNSS in combination with a geoid model. Thanks to the globally common definition, the height system can be used to exchange elevation information between different continents, which is not possible with traditional elevation systems that are regionally realised.
The definition of IHRS includes, among other things, a fixed value on the reference surface (the geoid) in the form of a value of the geopotential, W0, and that vertical positions are stated as the difference in geopotential values between the reference surface and the point in question, so-called potential numbers. These potential numbers can then be converted to traditional heights when needed. Using geopotentials instead of traditional height differences is done to avoid the effects of irregularities in the earth's gravitational field.
The work to realise the IHRS is ongoing, both globally and regionally. In Sweden, a research project was started in 2020 where one of the goals is to realise the IHRS in Sweden and the Nordic countries.
The IHRS is described in more detail in resolution no. 1 from IAG 2015 (pdf, new window). and thus facilitate the exchange of height information.
EVRS and EVRF
The European height system EVRS, European Vertical Reference System, is based on national levelling and land uplift data in order to create relationships between height systems in Europe, thereby facilitating exchange of height information.
Over the years, several common adjustments of the European height network have been made. The first two adjustments were denoted United European Leveling Network 55 (UELN 55) and UELN 73. After being at a standstill for a number of years, work resumed in 1995, resulting in UELN 95/98.
The definition of EVRS was adopted by EUREF (new window) in 2000. Height systems calculated according to this definition are said to be realisations of EVRS. UELN 95/98 formed the basis for the first realisation of EVRS which was named European Vertical Reference Frame 2000 (EVRF2000).
Through the years, levelling data have been updated and more countries have joined UELN which resulted in two additional realisations of EVRS; EVRF2007 and EVRF2019. EVRF2019 is the latest official realisation.
Data from the third preciselevelling in Sweden are included in UELN and RH 2000 is defined in accordance with EVRS, which means, among other things, that the zero level relates to Normaal Amsterdam Level (NAP) and that the heights consist of normal heights. Therefore the differences are small between RH 2000 and the European systems, EVRF2007 and EVRF2019.
More information
- German BKG informs about EVRS (new window)
- About European reference systems on the EUREF website (new window)
Baltic Sea Chart Datum 2000
The Baltic Sea Chart Datum 2000 - BSCD2000 - is a reference system intended for sea applications in the Baltic Sea such as hydrographic surveys and depth information in charts. The system entails a common reference surface for height and depth information for all countries around the Baltic Sea.
BSCD2000 is based on the definition of the European Vertical Reference System (EVRS) and has good compliance with the national height systems around the Baltic Sea. The zero level is in accordance with Normaal Amsterdams Peil (NAP) and the heights consist of normal heights. For Sweden, BSCD2000 connects to RH 2000 along the coast. Heights on land and depth information in charts consequently relate to the same zero level (NAP).
The purpose of BSCD2000 is to have a uniform system for depth information in the Baltic Sea and to promote the use of GNSS for accurate navigation and sea measurements at sea.
There is a geoid model to convert heights above the ellipsoid to heights in BSCD2000. The geoid model can be downloaded in three different formats, ASCII, GeoTiff and GTX (new window).
The Baltic Sea Hydrographic Commission which is responsible for BSCD2000, consists of members from all countries around the Baltic Sea. The Commission is working, among other things, on coordinating issues relating to hydrography and sea measurement in the Baltic Sea.
The Chart Datum, Water Level and Currents Working Group within the Baltic Sea Hydrographic Commission has more information about BSCD2000 (new window).