European Terrestrial Reference System 89 (ETRS89)
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ETRS89 definitions
The International Association of Geodesy (IAG) Subcommision for the European Reference Frame (EUREF), following its Resolution 1 adopted in the Firenze meeting in 1990, recommended that the terrestrial reference system to be adopted by EUREF would be coincident with ITRS at the epoch 1989.0 and fixed to the stable part of the Eurasian Plate. It was named European Terrestrial Reference System 89 (ETRS89). ETRS89 is the EU-recommended frame of reference for geodata for Europe. It is the only geodetic datum to be used for mapping and surveying purposes in Europe. It plays the same role for Europe as NAD83 for North America.
Since 1989.0 the ETRS89 and the ITRS diverge due to the continental drift at a speed about 2.5 cm per year. At present, the two coordinate systems differ by about 60 cm.
Defining parameters
ETRS89 uses the Geodetic Reference System 1980 (GRS80) ellipsoid as its reference ellipsoid with the geometric center of the ellipsoid coincident with the center of mass of the Earth and the origin of the coordinate system.
| Parameter | Notation | Value |
|---|---|---|
Semi-major Axis | a | 6378137.0 m |
Flattening Factor of the Earth | 1/f | 298.257222101 |
The difference between the GRS80 and WGS84 values for f creates a difference of 0.1 mm in the derived semi-minor axes of the two ellipsoids.
ETRS89 realizations
Both the EPSG database and the IGN ETRS89 website use 'ETRS89' without spaces between 'ETRS' and '89'.
| Geog 2D Code | Datum Code | Short Name | Datum Epoch | Area Code | Area Name | Remarks |
|---|---|---|---|---|---|---|
| 4258 | 6258 | ETRS89 | 1989.0 | 1298 | Europe | Fixed to the stable part of the Eurasian continental plate and consistent with ITRS at the epoch 1989.0. |
| ETRF89 | 1989.0 | The distinction in usage between ETRF89 and ETRS89 is confused: although in principle conceptually different in practice both are used for the realisation. | ||||
| ETRF2000 | 1989.0 | For each frame labelled ITRFyy a corresponding frame in ETRS89 can be computed and labelled ETRFyy. | ||||
| ETRF2000(R05) | 2000.0 | See remark below. | ||||
| ETRF2000(R08) | 2005.0 | See remark below. | ||||
| ETRF2014 | 2010.0 | See remark below. |
The EUREF Technical Working Group (TWG) recommends not to use the ETRF2005 and rather to adopt the ETRF2000 as a conventional frame of the ETRS89 system, see the Memo of Boucher and Altamimi for more details. This memo was first issued in 2001 and has been updated since then at each ITRF release. However, in order to benefit from the quality of ITRF2005 solution, the TWG has also recommended that all European stations coordinates (GNSS, VLBI, SLR and DORIS) which are available in the ITRF2005 to be expressed in the ETRF2000 frame and to call the resulting set of coordinates (positions and velocities) ETRF2000(R05). Similarly, the European station coordinates available in ITRF2008 solution were also expressed in ETRF2000 and the corresponding list is called ETRF2000(R08).
With regard to ETRF2014, the EUREF Technical Note 1 notes that "the adoption of a particular ETRS89 realization by a country will depend on various criteria which are beyond the scope of this Technical Note EUREF-TN-1. However, the adoption of ETRF2014 may be preferred for high precision applications and better consistency with the ITRF2014 precise geocentric origin, whereas ETRF2000 could be considered for geo-referencing purposes where agreement with realizations in neighbouring countries is of concern. The coordinate differences between ETRF2014 and ETRF2000 may reach up to 7cm."
Transformation parameters
Transformations between ETRS89 realizations and ITRF are given in ITRF_Transformation_Parameters_.xlsx (ETRS89 sheet).
Rotations are for the position vector rotation convention. Units are meters, mas (milliarcsecons) and ppb (parts-per-billion).
1 mas = 0.001 " = 2.77778 e-7 degrees = 4.84814 e-9 radians. 0.001 " corresponds to about 0.030 m at the earth's surface.
Note. Not all transformation parameters in the ETRS89 sheet have been tested. Always check the original documentation.
ETRS89, ITRF and WGS84
The ETRS89 (European Terrestrial Reference System of 1989) is based on ITRF89, epoch 1989.0 and monitored by a network of about 250 permanent GNSS tracking stations known as the EUREF Permanent Network (EPN). The IAG Sub-commission EUREF is responsible for the maintenance of the European Terrestrial Reference System (ETRS89). Check the EUREF web site: http://www.euref.eu. The EPN Central Bureau is located at the Royal Observatory of Belgium, http://www.epncb.oma.be.
New WGS84 realizations (since G730, 1994) are coincident with ITRF at about 10-centimeter level. For these realizations there are no official transformation parameters. This means that one can consider that ITRF coordinates are also expressed in WGS84 at 10 cm level. However, the most recent G1674 realization adopted ITRF2008 coordinates for more than half of the reference stations and velocities of nearby sites for the others. Thus, ITRF2008 and WGS84 (G1674) are likely to agree at the centimeter level, yielding conventional 0-transformation parameters. For more information, check ftp://itrf.ensg.ign.fr/pub/itrf/WGS84.TXT.
References
- IGN ETRS89 website - etrs89.ensg.ign.fr
- IAG EUREF sub-commision - www.euref.eu
- EUREF Permanent Network - epncb.oma.be