Meeting of the Working Party

/ EUROPEAN COMMISSION
STATISTICAL OFFICE OF THE EUROPEAN COMMUNITIES
Directorate E: Social and regional statistics and geographical information system
Unit E-4: Regional indicators and accounts, population and geographical information system /

Document: E/GIS/46/EN

Original

Meeting of the Working Party

"Geographical Information Systems for Statistics"

Joint meeting with National Statistical Offices

and National Mapping Agencies

Luxembourg, October 25-26, 2001

Bech Building (Room "Quételet")

Beginning of the meeting: 10 a.m.

______

Management summary of the conclusions of the ETeMII cartographic projection workshop

Document concerning item 6 of the agenda of Day 1 of the meeting

Mail: Bâtiment Jean Monnet, Rue Alcide de Gasperi, L-2920 Luxembourg
Offices: Bâtiment Joseph Bech, 5 Rue Alphonse Weicker, L-2721 Luxembourg - Office: BECH D3/733
Telephone: direct line (+352)4301.33411, switchboard 43011. Fax: 4301.34029
Telex: COMEU B 21877. Telegraphic address: COMEUR Luxembourg.

Conclusions of the Cartographic Projection Workshop

Abstract

Europe is a patchwork of several countries with different traditions in terms of their geographic choices. In a first workshop organised by the 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 established that a suitable candidate as European Spatial Reference System exists: ETRS89. We are now facing the problem of cartographic representation and grid storage of pan-European geographic data at different levels of precision. To discuss this subject a second workshop was organised, in which the main objective was to analyse the EC primary needs for map projection(s) and obtain expert advice to determine the appropriate projections. The results of the debate and the proposed recommendations are shortly illustrated in this document.

Introduction

In December 1999 in a workshop, organised by JRC and MEGRIN, the need of a common Spatial Reference System for Europe was discussed as a first step to ensure that geographic data are compatible across Europe. The workshop established that a suitable candidate as European Spatial Reference System exists: ETRS89. There was consensus amongst the experts that this is the system to adopt at European level and several countries have already done so. A European Spatial Reference System is not enough, we need a set of projection systems for the cartographic representation and grid storage of pan-European geographic data at different levels of precision. If we consider the current situation in Europe we have to admit that the situation seems rather discouraging. According to a recent survey of the situation in Europe we have 5 different types of reference ellipsoids and 8 different types of cartographic projections used in the 37 different CERCO member or observer countries. How could they agree on one single projection system and which one should be selected ? Which member countries would be able to afford the costs for changing their system ? Can a unique map projection be proposed ? 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, in which the main objective was to analyse the primary needs for map projection(s) in the European Commission and obtain expert advice to determine the appropriate projections. The Workshop took as the EC area of interest the current 15 member states and the 13 current candidate countries. The Workshop followed the similarly organised “Workshop on Spatial Reference Systems” of November 1999, and dealt with issues that could not have been addressed then. While unanimity was easily reached for the 1999 conclusions (basically: geographic ellipsoidal coordinates in ETRS89), this second Workshop had much more difficulties to reach a consensus. The main reason is that, while a unique Spatial Reference System is nearly totally scale- and application-independent, this is not the case with Cartographic Projections. The Workshop started with the users expressing nearly irreconcilable requirements and constraints, and conflicting suggestions for a unique Projection. Debates have been very rich, and convergence was gradually achieved on a set of recommendations, but also on the need for further work, from the experts (to clarify some technical issues and definitions) and from the European Commission (to continue the actions in the effect of harmonising the usage of coordinates systems with the GI users within the Commission and outside).

When map projection is needed by European Commission ?

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

·  Sampling (for example: data collection of statistical purposes);

·  storing (picture like satellite images, aerial orthophotos, .., but also raster representations of vector data like digital terrain models, slopes, land cover, …);

·  cartographic Display (both on paper maps or on screen);

·  measurements (measure of linear features, measure of areas, …). Overlays and measurements of areas and lengths should provide true areas and distances on this scale;

·  spatial analysis (integrated assessment using different spatial layers);

·  localisation (projected data are used to localise object on the ground);

·  conversion (data projected using National datum must be re-projected in ETRS89 to create pan-european data sets).

In addition we face the general problem of integration and harmonisation of data projected in different national systems. Should it be possible to convert from one projection system to another ? It is of overall importance to be compatible with coordinates measured with GPS. Should there be a collection of national projections with procedures for transforming one projection into another ?

Other boundaries conditions for the choice to be taken into account are:

·  some European projects still continue to work with National data bases (i.e. LPIS), other require the integration into a European system (i.e. I&CLC2000, GISxNatura2000), some will work with distributed data bases, …;

·  the accuracy and scale of the various projects is ranging from very precise data (i.e. LUCAS 1-2,5 m / 1:10,000) to global (i.e. FISIS 1:20,000,000);

·  some data are already available in GISCO other should be collected/created;

·  technical specifications are needed both for new data collection/creation and for existing data conversion;

·  the specifications/recommendations should foresee a stepwise approach to identify current solutions and to suggest a long term strategy for quality improvement;

·  in this sense the limitations of current GIS sw (and their future evolution - OGC specifications) should be taken into account.

Map projections to be used for European purposes

The following European projects/activities were considered during the discussion about suitable projections: Statistical Grids, LUCAS - Land Use / Cover Area Frame Statistical Survey, Nitrate directive. NATURA 2000, IMAGE 2000 and CORINE Land Cover 2000, Agro-Environmental Indicators. Trans-European-Networks, LPIS-Land Parcel Identification System.

The needs of the European Commission were clustered in relation to:

·  Vector data (thematic polygons, topographic etc); and

·  Raster data existing as both gridded information, and as images/ photographs (orthorectified or otherwise)

and considered the requirements of:

·  Storage (in a centralised database or in distributed databases);

·  Measurement (for instance, computing distance, area, etc); and

·  Displaying (on screen, paper maps, atlases etc).

The Workshop concluded that there would be significant cost resulting from the data conversion needed when adopting any new grid/projection system, but that changes were necessary due to the inadequacy for pan-European purposes of existing grid/projection systems in use within the EC.

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 EFTAS countries and the 13 current EU candidate members (“EU15+EFTAS+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 53°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[1], with the underlying GRS80[2] 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[3].

1. The European Commission should, as far as possible, use ellipsoidal (geodetic latitude, geodetic longitude, and if appropriate ellipsoidal height) co-ordinates related to ETRS89 for expressing and storing positions. In general ellipsoidal co-ordinates 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.

1. For conducting statistical analysis and display the Pan-European Equal Area coordinate reference system of 2001 (PEEA2001), an equal area projection of the ETRS89 coordinate reference system is recommended. The Lambert Azimuthal Equal Area projection with the centre of projection at 53°Nort and 10°East should be applied. In order to avoid negative coordinate values false northing and easting values are added to the projected coordinates. Further details of the recommended projections are given in proceedings of the workshop.

1. The European Commission should adopt the Pan-European Conformal coordinate reference system of 2001 (PEC2001) for conformal pan-European mapping at scales of smaller than 1:499,999 (1:500,000, 1:1,000,000,…). The workshop recommends to apply the Lambert Conformal Conical projection with standard parallels at 38° North and 61° North. The centre of the false origine is located at 53° North, 10°east. Values for False Easting and Northing are added to avoid negative coordinate values. Further details of the recommended projections are given in proceedings of the workshop.

1. The workshop recommends to adopt the Pan-European Transverse Mercator grid system (PETM) 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 and 1:499,999. The PETM consists of the Universal Transverse Mercator grid system applied to the ETRS89 coordinate reference system; details of the recommended projections are given in proceedings of the workshop.

1. The European Commission should maintain the PETM, the PEC2001 and the PEEA2001 as its standards for an extended period, in order to provide stability and confidence for data providers and users.

1. The European Commission should always identify coordinate reference systems and transformations in the format required by International Standard 19111.

Figure 2: The PETM2001 zones

Recommendations to National Mapping Agencies and EuroGeographics

The Workshop recognised that both the European standard coordinate reference systems and projections, and the current national (and local) systems will continue to co-exist for many years to come.

The Workshop noted that commonly encountered terms such as ‘UTM zone 32N’ without reference to the associated geodetic datum were ambiguous. It also noted that numerous existing procedures allow transformation or conversion of co-ordinates from one system to another. Some of these procedures are freely available, some are embedded in commercial software, yet many are reserved for internal use and not publicly distributed. There is a multitude of user-defined relationships in use. There is an urgent EC business need to implement a single set of officially recognised transformations.

Specific recommendations for National Mapping Agencies and EuroGeographics are:

·  to always identify coordinate reference systems in the format required by ISO-19111 (which currently exists as a Draft International Standard);

·  national coordinate reference systems be compatible with EC standards wherever possible;

·  transformation parameters and formulae between national coordinate reference systems and ETRS89 providing co-ordinates of an accuracy at the 1~2m level should be placed in the public domain at the earliest possible opportunity and the availability of the information should be made widely known;

·  the availability of more accurate transformations should also be indicated (with the achievable accuracy and the official source of information).

Further Recommendations to EC

1. The European Commission should stimulate the use, by preference, one of the above defined projection for screen display or prints, except when specific needs of applications or projects require otherwise.

1. The European Commission should take strong action to support the work of EUREF and EuroGeographics in collecting and making publicly available the definitions of various coordinate reference systems, and definitive transformation parameters between ETRS89, EVRF2000 and national systems.

1. The European Commission should continue to support EuroGeographics in encouraging National Mapping Agencies to develop national systems which are compatible with the pan-European coordinate reference systems.

1. A single indexing system for statistical purposes should be researched, seeking a multi-resolution solution for an equal area gridding system. The nodes of the grid cells should be expressed in ETRS89 ellipsoidal coordinates, or PEEA2001 grid coordinates.

1. Calculations for sea limits etc should be computed on the ETRS89 coordinate reference system and that GIS buffering should not be used in the calculation or depiction of these important points and lines. The results should be held as vectors.

1. The need for a further Workshop on these issues, and the needs of the world map for fisheries, should be considered.

Conclusions