GISCO Database Manual - part 1 - chapter 3

Update: 07/2003

Important Note by Marc Van Liedekerke (01/02/08): This version of the Database Manual is obsolete in relation to the most recent developments of the GISCO data. However, this version of the documentation still serves to explain the co-ordinate reference system used by a few datasets maintained in European Soil Portal; these datasets historically used the LAEA co-ordinate system explained under Chapter-3.


Spatial Reference System

Projection systems

A map is a graphic representation of geographical features or other spatial phenomena. Both location and attribute information of a particular object can be read from a map. The location information describes the position of the object on the earth's surface, while the attribute information describes characteristics of the features represented.

In addition to feature locations and their attributes, maps have other technical characteristics that define them and their use. These include scale, resolution, accuracy and projection.

The map scale is the extent of reduction necessary to display a representation of the earth's surface on a map. It is often expressed as a representative fraction of distance, such as
1:1 000 000. This means that 1 unit of distance on the map represents 1 million of the same units of distance on the earth.

Map resolution is the accuracy with which the location and shape of map features can be depicted for a given map scale. In addition to this, maps also contain accuracy constraints in the placement of lines and points on the map page.

A map projection is a mathematical transformation to calculate the position of a geographical feature from its position on the 3-dimensional earth's surface to its position on a 2-dimensional map surface.

The earth is almost a perfect sphere. The ellipticity is approximately 0.003353. To simplify mathematical calculations, the earth is often considered to be a sphere, with a certain radius. This assumption can be used for maps with a scale up to 1:5 000 000. At this scale, one cannot detect the difference between a sphere and a spheroid on a map. For larger scale maps, however, it is necessary to treat the earth as a spheroid (i.e. an ellipsoid which approximates to a sphere).

Because of gravitational variations and variations in surface features, the earth is not a perfect spheroid. Many surveys of the irregularities of the earth's surface have led to the definition of many spheroids. The semi-major and semi-minor axes defining the spheroid that best fit one geographic region are not necessarily the same for another geographic region.

Spherical coordinates are measured in latitude and longitude. If the earth is considered to be a sphere, latitude and longitude are angles measured from the earth's centre to a point on the earth' surface. Latitude and longitude are measured in degrees, minutes and seconds. The equator has latitude 0°, the North Pole 90°, and the South Pole -90°. The Prime Meridian, indicating a longitude of 0°, starts at the North Pole, passes through Greenwich, England, and ends at the South Pole.

Although measurements of latitude and longitude can be used to locate the exact position of a feature on the earth's surface, these measurement units are not associated with a standard length. It is only along the Equator that the distance represented by one degree of longitude approximates the distance represented by one degree of latitude.

To obtain comparable measurement units on a map, a mathematical conversion is needed. This transformation is commonly referred to as a "map projection".

There are four basic properties to map projections: shape - area - distance - direction.

Any representation of the ellipsoid surface in a 2-dimensional map causes distortion of one or more of these map properties. As different projections produce different distortions, they are suitable for some applications but not useful for others.

The GISCO Database Reference System

The GISCO locational reference system is the geographical coordinate system measured in latitude and longitude on a spheroid with a specific datum known as ETRS89. This system can be used to identify the locations of points anywhere on the earth's surface and is commonly refered to as the Geographical Reference System.

Longitude lines are also called meridians and stretch between the North and South poles, whereas latitude lines are also called parallels and encircle the globe with parallel rings.

The geodetic latitude (there are many other defined latitudes) of a point is the angle from the equatorial plane to the vertical direction of a line normal to the reference ellipsoid.

The geodetic longitude of a point is the angle between a reference plane and a plane passing through the point, both planes being perpendicular to the equatorial plane.

Latitude and longitude are commonly either measured in degrees, minutes and seconds or decimal degrees, the latter being the GISCO measurement unit. Latitude values range from 0° at the equator to +90° at the North Pole and -90° at the South Pole. Longitude ranges from 0° at the Prime Meridian (the meridian that passes through Greenwich, England) to 180° when traveling East from 0° and -180° when traveling West fom 0°.

Since longitude lines converge at the poles and converge towards the equator, one degree longitude varies between zero and 111 km at the equator. Therefore, degrees can not be associated with a standard length and furthermore, can not be used as an accurate measure of distance or area.

In order to provide measure of area and length, *.le for length and *.ar for area, info tables have been added to all layers with arc, polygon or region features. The measure is calculated on the basis of the Lambert Azimuthal Equal Area projection.

To demonstrate these tables, the example of the structural funds (SF) version 5 in the community support (cs) theme, will be used:

The SFEC1MV5 cover consists of the following features:

Feature TypeTable Name
Associated Area or Length Table
arcsfec1mv5.aat
sfec1mv5.le
polygonsfec1mv5.pat
sfec1mv5.ar
regionsfec1mv5.patsfelcl
sfec1mv5.arsfelcl etc.

The *.ar and *.le tables can be linked to their corresponding feature tables via the <TABLE-NAME>-ID item. The corresponding relationships can be defined as follows:

Notably, an Arc coverage does not have a one-to-one relationship with its *.le table. Since the convertion from Lambert Azimuthal Equal Area to Geographic Coordinates split some arcs, the relationship from the Arc coverage to the *.le table is one-or-many to one.

Exceptions

The table below gives an overview of all data sets that are not projected in Geographic Coordinates and Spheroid ETRS89. Added are the reference systems they are projected in. In principle, grids are not projected as Geographic Coordinates, but as indicated in the table below. These projection systems are described in the chapters that follow.

Data SetProjection Spheroid
alwdgg None (geographical coordinates)Clarke 1866
deeu20m Lambert Azimuth Equal Area Semi major axis of International 1909
deeu3m Lambert Azimuth Equal Area Semi major axis of International 1909
fawd25mgg None (geographical coordinates)Clarke 1866
lceugr Lambert Azimuth Equal Area Semi major axis of International 1909
wawdgg None (geographical coordinates)Clarke 1866

The Lambert Azimuthal Equal Area projection

The Lambert Azimuthal Equal Area projection is a planar projection, which means that map data are projected onto a flat surface. The aritmethic centre of the projection, or the point of tangency, is a single point specified by longitude and latitude that can be located anywhere. This projection preserves the area of individual polygons while simultaneously maintaining a true sense of direction from the centre and is best suited for individual land masses that are symmetrically proportioned.

This projection system used to be the standard reference system for the GISCO Database until the release of november 2002. In order to convert coverages, in former projection systems (before 11/2002) of the GISCO Database, to ETRS89 a usertool has been developed. This tool can be found as $GCAI/atool/arc/la2gc.aml.

Usage : la2gc < input coverage > (a path name can be specified)

The GISCO Lambert Azimuthal Equal area projection is characterised by the following parameters:

Unitsmeters
Spheroidsphere
Parameters
Radius of sphere of reference6378388
Longitude of centre of projection09° 00' 00"
Latitude of centre of projection48° 00' 00"
False easting0.0
False northing0.0

Other map projections used in the GISCO reference database

The French overseas areas (DOM: Départements Outre Mer) that are grids, are projected according to different parameters:

For the DOM areas, a Lambert Conformal projection is used, with parameters matched to every region:

RéunionUnits meters
SpheroidInternational 1909
Parameters
1st standard parallel -20° 0' 0.000"
2nd standard parallel -22° 0' 0.000"
central meridian55° 30' 0.000"
latitude of projection's origin -21° 0' 0.000"
GuyaneUnits meters
SpheroidInternational 1909
Parameters
1st standard parallel 2° 0' 0.000"
2nd standard parallel 6° 0' 0.000"
central meridian-53° 0' 0.000"
latitude of projection's origin 4° 0' 0.000"
MartiniqueUnits meters
SpheroidInternational 1909
Parameters
1st standard parallel 14° 0' 0.000"
2nd standard parallel 15° 0' 0.000"
central meridian-61° 0' 0.000"
latitude of projection's origin 14° 30' 0.000"
GuadeloupeUnits meters
SpheroidInternational 1909
Parameters
1st standard parallel 16° 0' 0.000"
2nd standard parallel 16° 30' 0.000"
central meridian-61° 30' 0.000"
latitude of projection's origin 16° 15' 0.000"

The New Spatial Reference System and Map Projections

In December 1999 in a workshop, organised by JRC and MEGRIN, the need of a common Spatial Reference System for Europe was discussed as first step to ensure that geographic data are compatible across Europe. The workshop recommended to adopt the European Spatial Reference System ETRS89 at European level. But, a European Spatial Reference System is not enough, there is a need for a set of projection systems for the cartographic representation and grid storage of Pan-European geographic data at different levels of precision. To discuss this subject the JRC and EuroGeographics organised a second workshop (Dec. 14th - 15th 2000, Marne-la-Vallée) with a panel of relevant experts, with the main objective being to analyse the European Commission primary needs for map projection(s) and obtains expert advice to determine the appropriate projections.

The Needs of the European Commission for Map Projections

Projected data are used in different contexts and for different uses:

The Workshop noted the need for a Pan-European coordinate reference system in which area remains true (for many statistical purposes) and which also maintains angles and shapes (for purposes such as topographic mapping). These needs cannot be met through usage of the ETRS89 ellipsoidal coordinate reference system alone, and a map projection is required to supplement the ellipsoidal system. The Workshop recognised that mapping of the ellipsoid cannot be achieved without distortion, and that it is impossible to satisfy the maintenance of area, direction and shape through a single projection.

For the purposes of evaluating projection distortion, the area of interest was taken to be a primary area equating to the EU15 except for outlying islands in the Atlantic (Madeira, Canaries, etc) ("EU15"), and a secondary area covering the current EU15 including Atlantic islands plus the EFTA countries and the 13 current EU candidate countries ("EU15+EFTA+CEC13"). In addition, the secondary area was extended eastwards to the Ural Mountains "Geographic Europe".

The primary area is bounded by parallels of 71°N and 34°N and meridians of 11°W and 32°E whilst the secondary area is bounded by parallels of 82°N and 27°N and meridians of 32°W and 45°E. The eastern boundary of the secondary area extension is 70°E. The centre of the area of interest was taken to be 52°N, 10°E.

Figure 1: The Area of Interest

Main Recommendations to the European Commission

  1. The workshop reaffirmed the recommendations of the previous workshop to express and store positions in ellipsoidal coordinates related to ETRS89 , with the underlying GRS80 ellipsoid, and to further adopt EVRF2000 for expressing physical heights. For coordinate accuracies of > 1m, the ETRS89 can be regarded as equal to the WGS84 .
  2. The European Commission should, as far as possible, use ellipsoidal (geodetic latitude, geodetic longitude, and if appropriate ellipsoidal height) coordinates related to ETRS89 for expressing and storing positions. In general, ellipsoidal coordinates should be used for storing vector data. Raster data should be stored in one of the recommended coordinate reference system. The choice of the appropriate system should be based on the objectives of the data. Full consideration should be given to resampling when moving raster data between coordinate reference systems, with expert advice taken on matters such as pixel size.
  3. For conducting statistical analysis and display the Pan-European Equal Area coordinate reference system of 2001 (ETRS-LAEA), an equal area projection of the ETRS89 coordinate reference system is recommended.
  4. The European Commission should adopt the Pan-European Conformal coordinate reference system of 2001 (ETRS-LCC) for conformal Pan-European mapping at scales of smaller or equal to 1:500,000 (1:1,000,000,...).
  5. The workshop recommends to adopt the Pan-European Transverse Mercator grid system (ETRS-TMzn) for its applications requiring a conformal projection, including large-scale topographic mapping, when the collection scale of the mapping data is between 1:10,000 - < 1:500,000. The ETRS-TMzn consists of the Universal Transverse Mercator grid system applied to the ETRS89 coordinate reference system.

At the COGI meeting in May 2001, all participants agreed that the coordinate reference system ETRS89 should be adopted by all Commission services using GIS or collecting geo-referenced data. This agreement was affirmed by a formal decision of the European Commission to use ETRS89 for expressing geographical locations.

ETRS89 Ellipsoidal Coordinate Reference System (ETRS89)

The European Terrestrial Reference System 1989 (ETRS89) is the geodetic datum for Pan-European spatial data collection, storage and analysis. This is based on the GRS80 ellipsoid and is the basis for a coordinate reference system using ellipsoidal coordinates. The ETRS89 Ellipsoidal Coordinate Reference System (ETRS89) is recommended to express and to store positions, as far as possible.

Definition

Table 1 contains the fully described ETRS89 Ellipsoidal Coordinate Reference System (ETRS89) following ISO 19111 Spatial referencing by coordinates.

Table 1: ETRS89 Ellipsoidal Coordinate Reference System Description

Entity Value
CRS ID ETRS89
CRS alias ETRS89 Ellipsoidal CRS
CRS valid area Europe
CRS scope Geodesy, Cartography, Geoinformation systems, Mapping
Datum ID ETRS89
Datum alias European Terrestrial Reference System 1989
Datum type geodetic
Datum realization epoch 1989
Datum valid area Europe / EUREF
Datum scope European datum consistent with ITRS at the epoch 1989.0 and fixed to the stable part of the Eurasian continental plate for georeferencing of GIS and geokinematic tasks
Datum remarks see Boucher, C., Altamimi, Z. (1992): The EUREF Terrestrial Reference System and its First Realizations. Veröffentlichungen der Bayerischen Kommission für die Internationale Erdmessung, Heft 52, München 1992, pages 205-213- or ftp://lareg.ensg.ign.fr/pub/euref/info/guidelines/
Prime meridian ID Greenwich
Prime meridian Greenwich longitude
Ellipsoid ID GRS 80
Ellipsoid alias New International
Ellipsoid semi-major axis 6 378 137 m
Ellipsoid shape TRUE
Ellipsoid inverse flattening 298.2572221
Ellipsoid remarks see Moritz, H. (1988): Geodetic Reference System 1980. Bulletin Geodesique, The Geodesists Handbook, 1988, Internat. Union of Geodesy and Geophysics
Coordinate system ID Ellipsoidal Coordinate System
Coordinate system type geodetic
Coordinate system dimension 3
Coordinate system axis name geodetic latitude
Coordinate system axis direction North
Coordinate system axis unit identifier degree
Coordinate system axis name geodetic longitude
Coordinate system axis direction East
Coordinate system axis unit identifier degree
Coordinate system axis name ellipsoidal height
Coordinate system axis direction up
Coordinate system axis unit identifier metre

Relationship between Ellipsoidal and Cartesian Coordinates

The coordinate lines of the Ellipsoidal Coordinate System are curvilinear lines on the surface of the ellipsoid. They are called parallels for constant latitude (phi) and meridians for constant longitude (lamda). When the ellipsoid is related to the shape of the Earth, the ellipsoidal coordinates are named geodetic coordinates. In some cases the term geographic coordinate system usually implies a geodetic coordinate system.

Figure 2: Cartesian Coordinates and Ellipsoidal Coordinates

picture╠╠.

If the origin of a right-handed Cartesian coordinate system coincides with the centre of the ellipsoid, the Cartesian Z-axis coincides with the axis of rotation of the ellipsoid and the positive X-axis passes through the point "phi" = 0, "lamda" = 0.

ETRS89 Lambert Azimuthal Equal Area Coordinate Reference System (ETRS-LAEA)

The European Terrestrial Reference System 1989 (ETRS89) is the geodetic datum for Pan-European spatial data collection, storage and analysis. This is based on the GRS80 ellipsoid and is the basis for a coordinate reference system using ellipsoidal coordinates. For many Pan-European purposes a plane coordinate system is preferred. But the mapping of ellipsoidal coordinates to plane coordinates cannot be made without distortion in the plane coordinate system. Distortion can be controlled, but not avoided.

For many purposes the plane coordinate system should have minimum distortion of scale and direction. This can be achieved through a conformal map projection. The ETRS89 Transverse Mercator Coordinate Reference System (ETRS-TMzn) is recommended for conformal Pan-European mapping at scales larger than 1:500 000. For Pan-European conformal mapping at scales smaller or equal 1:500 000 the ETRS89 Lambert Conformal Conic Coordinate Reference System (ETRS-LCC) is recommended.

With conformal projection methods attributes such as area will not be free of distortion. For Pan-European statistical mapping at all scales or for other purposes where true area representation is required, the ETRS89 Lambert Azimuthal Equal Area Coordinate Reference System (ETRS-LAEA) is recommended.

Definition

The ETRS89 Lambert Azimuthal Equal Area Coordinate Reference System (ETRS-LAEA) is a single projected coordinate reference system for all of the Pan-European area. It is based on the ETRS89 geodetic datum and the GRS80 ellipsoid. Its defining parameters are given in Table 2 following ISO 19111 Spatial referencing by coordinates.

Table 2: ETRS-LAEA Description

Entity Value
CRS ID ETRS-LAEA
CRS alias ETRS89 Lambert Azimuthal Equal Area CRS
CRS valid area Europe
CRS scope CRS for Pan-European statistical mapping at all scales or other purposes where true area representation is required
Datum ID ETRS89
Datum alias European Terrestrial Reference System 1989
Datum type geodetic
Datum realization epoch 1989
Datum valid area Europe / EUREF
Datum scope European datum consistent with ITRS at the epoch 1989.0 and fixed to the stable part of the Eurasian continental plate for georeferencing of GIS and geokinematic tasks
Datum remarks see Boucher, C., Altamimi, Z. (1992): The EUREF Terrestrial Reference System and its First Realizations. Veröffentlichungen der Bayerischen Kommission für die Internationale Erdmessung, Heft 52, München 1992, pages 205-213 - or ftp://lareg.ensg.ign.fr/pub/euref/info/guidelines
Prime meridian ID Greenwich
Prime meridian Greenwich longitude
Ellipsoid ID GRS 80
Ellipsoid alias New International
Ellipsoid semi-major axis 6 378 137 m
Ellipsoid shape TRUE
Ellipsoid inverse flattening 298.2572221
Ellipsoid remarks see Moritz, H. (1988): Geodetic Reference System 1980. Bulletin Geodesique, The Geodesists Handbook, 1988, Internat. Union of Geodesy and Geophysics
Coordinate system ID LAEA
Coordinate system type projected
Coordinate system dimension 2
Coordinate system axis name Y
Coordinate system axis direction North
Coordinate system axis unit identifier metre
Coordinate system axis name X
Coordinate system axis direction East
Coordinate system axis unit identifier metre
Operation ID LAEA
Operation valid area Europe
Operation scope for Pan-European statistical mapping at all scales or other purposes where true area representation is required
Operation method name Lambert Azimuthal Equal Area Projection
Operation method formula US Geological Survey Professional Publication 1395, "Map Projection - A Working Manual" by John P. Snyder.
Operation method parameters number 4
Operation parameter name latitude of origin
Operation parameter value 52° N
Operation parameter name longitude of origin
Operation parameter value 10° E
Operation parameter remarks
Operation parameter name false northing
Operation parameter value 3 210 000.0 m
Operation parameter remarks
Operation parameter name false easting
Operation parameter value 4 321 000.0 m
Operation parameter remarks

With these defining parameters, locations North of 25° have positive grid northing and locations eastwards of 30° West longitude have positive grid easting. Note that the axes abbreviations for ETRS-LAEA are Y and X whilst for the ETRS-LCC and ETRS-TMnz they are N and E.

Caution

All EU projections are based on ETRS89 datum and therefore use ellipsoidal formulas. In some GIS applications the Lambert Azimuthal Equal Area method is implemented only in spherical form. Geodetic latitude and longitude must not be used in these spherical implementations. To do so may cause significant error (up to 15 km !). Use the example conversions above to test whether software uses appropriate formulas.

ETRS89 Lambert Conformal Conic Coordinate Reference System (ETRS-LCC) (ETRS-LAEA)

The European Terrestrial Reference System 1989 (ETRS89) is the geodetic datum for Pan-European spatial data collection, storage and analysis. This is based on the GRS80 ellipsoid and is the basis for a coordinate reference system using ellipsoidal coordinates. For many Pan-European purposes a plane coordinate system is preferred. But the mapping of ellipsoidal coordinates to plane coordinates cannot be made without distortion in the plane coordinate system. Distortion can be controlled, but not avoided. For many purposes the plane coordinate system should have minimum distortion of scale and direction. This can be achieved through a conformal map projection.

The ETRS89 Lambert Conformal Conic Coordinate Reference System (ETRS-LCC) is recommended for conformal Pan-European mapping at scales smaller or equal 1:500 000. For Pan-European conformal mapping at scales larger than 1:500 000 the ETRS89 Transverse Mercator Coordinate Reference System (ETRS-TMzn) is recommended.

With conformal projection methods attributes such as area will not be distortion-free. For Pan-European statistical mapping at all scales or other purposes where true area representation is required, the ETRS89 Lambert Azimuthal Equal Area Coordinate Reference System is recommended.

Definition

The ETRS89 Lambert Conformal Conic Coordinate Reference System (ETRS-LCC) is a single projected coordinate reference system for all of the Pan-European area applied to the ETRS89 geodetic datum and the GRS80 ellipsoid. Because of the greater extent in longitude than in latitude, a Lambert Conic Conformal projection with two standard parallels is utilised.

The scale factor is only a function of the latitudes of the standard parallels and the latitude of the point where it is computed. Figure 3 shows the variation of the scale factor k against latitude. The maximum and minimum values are shown in Table 3, also in parts per million (ppm).

Figure 3: Variation of the Scale Factor

Table 3: Maximum and Minimum Values of the Distortion

Extreme Latitude Scale factor k Scale (ppm)
minimum 51°N (circa) 0.965 622 -34 378
maximum 71° N 1.043 704 43 704

Defining parameters are given in Table 4 following ISO 19111 Spatial referencing by coordinates.


Table 4: ETRS-LCC Description

Entitiy Value
CRS ID ETRS-LCC
CRS alias ETRS89 Lambert Conformal Conic CRS
CRS valid area Europe
CRS scope CRS for conformal Pan-European mapping at scales smaller or equal 1:500 000
Datum ID ETRS89
Datum alias European Terrestrial Reference System 1989
Datum type geodetic
Datum realization epoch 1989
Datum valid area Europe / EUREF
Datum scope European datum consistent with ITRS at the epoch 1989.0 and fixed to the stable part of the Eurasian continental plate for georeferencing of GIS and geokinematic tasks
Datum remarks see Boucher, C., Altamimi, Z. (1992): The EUREF Terrestrial Reference System and its First Realizations. Veröffentlichungen der Bayerischen Kommission für die Internationale Erdmessung, Heft 52, München 1992, pages 205-213- or ftp://lareg.ensg.ign.fr/pub/euref/info/guidelines/
Prime meridian ID Greenwich
Prime meridian Greenwich longitude
Ellipsoid ID GRS 80
Ellipsoid alias New International
Ellipsoid semi-major axis 6 378 137 m
Ellipsoid shape TRUE
Ellipsoid inverse flattening 298.2572221
Ellipsoid remarks see Moritz, H. (1988): Geodetic Reference System 1980. Bulletin Geodesique, The Geodesists Handbook, 1988, Internat. Union of Geodesy and Geophysics
Coordinate system ID LCC
Coordinate system type projected
Coordinate system dimension 2
Coordinate system axis name N
Coordinate system axis direction North
Coordinate system axis unit identifier metre
Coordinate system axis name E
Coordinate system axis direction East
Coordinate system axis unit identifier metre
Operation ID LCC
Operation valid area Europe
Operation scope for conformal Pan-European mapping at scales smaller or equal 1 : 500 000
Operation method name Lambert Conformal Conic Projection with 2 standard parallels
Operation method formula Lambert Conformal Conic Projection, in Hooijberg, Practical Geodesy, 1997, pages 133-139
Operation method parameters number 6
Operation parameter name lower parallel
Operation parameter value 35° N
Operation parameter remarks
Operation parameter name upper parallel
Operation parameter value 65° N
Operation parameter remarks
Operation parameter name latitude grid origin
Operation parameter value 52° N
Operation parameter remarks
Operation parameter name longitude grid origin
Operation parameter value 10° E
Operation parameter remarks
Operation parameter name false northing
Operation parameter value 2 800 000 m
Operation parameter remarks
Operation parameter name false easting
Operation parameter value 4 000 000 m
Operation parameter remarks

Note that the axes abbreviations for ETRS-LCC and ETRS-TMzn are N and E whilst for the ETRS-LAEA they are Y and X.

ETRS89 Transverse Mercator Coordinate Reference System (ETRS-TMzn)

The European Terrestrial Reference System 1989 (ETRS89) is the geodetic datum for Pan-European spatial data collection, storage and analysis. This is based on the GRS80 ellipsoid and is the basis for a coordinate reference system using ellipsoidal coordinates. For many Pan-European purposes a plane coordinate system is preferred. But the mapping of ellipsoidal coordinates to plane coordinates cannot be made without distortion in the plane coordinate system. Distortion can be controlled, but not avoided. For many purposes the plane coordinate system should have minimum distortion of scale and direction. This can be achieved through a conformal map projection.

The ETRS89 Transverse Mercator Coordinate Reference System (ETRS-TMzn) is recommended for conformal Pan-European mapping at scales larger than 1:500 000. For Pan-European conformal mapping at scales smaller or equal 1:500 000 the ETRS89 Lambert Conformal Conic Coordinate Reference System (ETRS-LCC) is recommended.

With conformal projection methods attributes such as area will not be distortion-free. For Pan-European statistical mapping at all scales or other purposes where true area representation is required, the ETRS89 Lambert Azimuthal Equal Area Coordinate Reference System is recommended.

Definition

The ETRS89 Transverse Mercator Coordinate Reference System (ETRS-TMzn) is identical to the Universal Transverse Mercator grid system for the northern Hemisphere applied to the ETRS89 geodetic datum and the GRS80 ellipsoid. The UTM system was developed for worldwide application between 80°S and 84°N with the following basic features:

  1. 60 zones of 6° longitudinal extension numbered consecutively from 1 to 60, beginning with number 1 for the zone between 180°W and 174°W and continuing eastward
  2. central meridian scale factor of 0.9996 producing two lines of secancy approximately 180 000 m East and West of the central meridian
  3. negative coordinates are avoided by assigning a false easting value of 500 000 m East at the central meridian; and false northing values at the equator of 0 m for the northern hemisphere and 10 000 000 m for the southern hemisphere
  4. uniform conversion formulas from one zone to another
  5. unique referencing for all zones in a plane rectangular coordinate system
  6. meridional convergence (between the true and grid North) to be less than 5
  7. map distortion within the zones to be less than 1 : 2500

ETRS-TMzn is a series of zones, where "zn" in the identifier is the zone number. Each zone runs from the equator northwards to latitude 84° North and is 6-degrees wide in longitude reckoned from the Greenwich prime meridian. Zone 31 is centred on 3° East and is used between 0° and 6° East, zone 32 is centred on 9° East and is used between 6° and 12° East, etc. Table 5 shows the zones of the ETRS-TMzn.

Table 5: Zones of ETRS89 Transverse Mercator Coordinate Reference System

Zone number Longitude of Origin West Limit East Limit South Limit North Limit
(zn) (degrees) (degrees) (degrees) (degrees) (degrees)
26 27° West 30° West 24° West 0° North 84° North
27 21° West 24° West 18° West 0° North 84° North
28 15° West 18° West 12° West 0° North 84° North
29 9° West 12° West 6° West 0° North 84° North
30 3° West 6° West 0° East 0° North 84° North
31 3° East 0° East 6° East 0° North 84° North
32 9° East 6° East 12° East 0° North 84° North
33 15° East 12° East 18° East 0° North 84° North
34 21° East 18° East 24° East 0° North 84° North
35 27° East 24° East 30° East 0° North 84° North
36 33° East 30° East 36° East 0° North 84° North
37 39° East 36° East 42° East 0° North 84° North
38 45° East 42° East 48° East 0° North 84° North
39 51° East 48° East 54° East 0° North 84° North

Figure 4: The ETRS-TMzn Zones

Table 6 contains the fully described ETRS89 Transverse Mercator Coordinate Reference System (ETRS-TMzn) following ISO 19111 Spatial referencing by coordinates.

Table 6: ETRS-TMzn Description

Entity Value
CRS ID ETRS-TMzn
CRS remarks zn is the zone number, starting with 1 on the zone from 180° West to 174° West, increasing eastwards to 60 on the zone from 174° East to 180° East
CRS alias ETRS89 Transverse Mercator CRS
CRS valid area Europe
CRS scope CRS for conformal pan-European mapping at scales larger than 1:500 000

Datum ID ETRS89
Datum alias European Terrestrial Reference System 1989
Datum type geodetic
Datum realization epoch 1989
Datum valid area Europe / EUREF
Datum scope European datum consistent with ITRS at the epoch 1989.0 and fixed to the stable part of the Eurasian continental plate for georeferencing of GIS and geokinematic tasks
Datum remarks see Boucher, C., Altamimi, Z. (1992): The EUREF Terrestrial Reference System and its First Realizations. Veröffentlichungen der Bayerischen Kommission für die Internationale Erdmessung, Heft 52, München 1992, pages 205-213 - or ftp://lareg.ensg.ign.fr/pub/euref/info/guidelines/

Prime meridian ID Greenwich
Prime meridian Greenwich longitude
Ellipsoid ID GRS 80
Ellipsoid alias New International
Ellipsoid semi-major axis 6 378 137 m
Ellipsoid shape TRUE
Ellipsoid inverse flattening 298.2572221
Ellipsoid remarks see Moritz, H. (1988): Geodetic Reference System 1980. Bulletin Geodesique, The Geodesists Handbook, 1988, Internat. Union of Geodesy and Geophysics
Coordinate system ID TMzn
Coordinate system type projected
Coordinate system dimension 2
Coordinate system remarks Projection: Transverse Mercator in zones, 6° width
Coordinate system axis name N
Coordinate system axis direction North
Coordinate system axis unit identifier metre
Coordinate system axis name E
Coordinate system axis direction East
Coordinate system axis unit identifier metre
Operation ID TMzn
Operation valid area Europe
Operation scope for conformal pan-European mapping at scales larger than 1:500 000
Operation method name Transverse Mercator Projection
Operation method name alias TMzn
Operation method formula Transverse Mercator Mapping Equations, in Hooijberg, Practical Geodesy, 1997, pages 81-84, 111-114
Operation method parameters number 7
Operation parameter name latitude of origin
Operation parameter value
Operation parameter remarks 0°, the Equator
Operation parameter name longitude of origin
Operation parameter value central meridian (CM) of each zone
Operation parameter remarks central meridians ...,3° W, 3° E, 9° E, 15° E, 21° E,...
Operation parameter name false northing
Operation parameter value 0 m
Operation parameter remarks
Operation parameter name false easting
Operation parameter value 500 000 m
Operation parameter remarks
Operation parameter name scale factor at central meridian
Operation parameter value 0.9996
Operation parameter remarks
Operation parameter name width of zones
Operation parameter value
Operation parameter remarks
Operation parameter name latitude limits of system
Operation parameter value 0° N and 84° N
Operation parameter remarks

Note that the axes abbreviations for ETRS-TMzn and ETRS-LCC are N and E whilst for the ETRS-LAEA they are Y and X.

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