Vector CLC database was provided by National Teams within original CLC1990, I&CLC2000 update and FTSP/CLC2006 update projects. All features in original vector database were classified and digitised based on satellite images with 100 m positional accuracy (according to CLC specifications) and 25 ha minimum mapping unit into the standardized CLC nomenclature (44 CLC classes). European Corine Land Cover seamless DBs represent the final product of European data integration. The process of data integration started when national deliveries have been accepted and the Database Acceptance Report (DBTA) delivered . Delivered national data were produced in local national systems of all participating countries. Each national Coordinate Reference System (CRS) definition had to be known precisely together with its geometric relationship to a standard system in order to accurately transfer all national data into a standard European coordinate reference - ETRS89/LAEA1052. Mostly, the process itself was carried out by global equation-based transformation to ETRS89 (e.g. seven-parameters Bursa-Wolf methods). The accuracy of a particular transformation ranges from centimetres to meters depending on the method and the quality and number of control points available to define the transformation parameters, but, in any case, the accuracy is far above the actual CLC data resolution (for more details see the DBTA reports for particular country). National data, when transformed into the common European reference, are introduced into tiled pan-European structure and as final step seamless dataset is produced. In order to achieve production of the real seamless European database, the integration step includes also harmonization of database along country borders. It consists from edge-matching of land cover polygons from the national databases across national borders done by a verification / re-interpretation of the satellite images in the border regions (2 km wide strip along borders). The satellite images from IMAGE2000. CLC90, CHA00 and CLC00 database were harmonized this way, but the order to priority was as following: CLC2000, both geometric and thematic adaptations of all polygons in a 2 km strip along national boundary lines; CHA00 database to ensure that changes in CLC2000 are consistent with the change database; corrected CLC90 (if provided by the MS); corrections were focused to geometric adaptations in semi-automatical way based on CLC00 and CHA00 databases. Border harmonization step has been skipped for CHA06 and CLC06 datasets. Note: Some artificial lines (dividing polygons with the same code) can be still present in database due to technical constraints of current ArcGIS technology, but has no impact for dataset contents and can be dissolved for data extracts.

CHANGES:Version 16 (V4) (04/2012) Production date: April 15th, 2012

Release history: V4: 04/2012 - Upgraded version - Erroneously classiffied polygon on DE/BE boundary has been repaired. - Small pieces of 523 class in Elbe estuaries has been repaired. - Reprojected CLC06 data for Malta are included.

V3: 07/2011 - Upgraded version - Great Britain included - Sea buffer (25km) improved so they are consistent across all CLC layers A simplified border matching has been applied for CH, NO, KO, TR, IE :

- <25 ha polygons are NOT systematically removed (see next bullet).

- Sliver-like polygons (area < cca. 5 ha - soft limit) are generalised to largest or thematically most similar neighbour.

- CLC-code differences in polygons along two sides of the border are NOT changed

- Version numbering changed to be consistent across all CLC layers

- Contains data for 38 countries

V2: 10/2010 - Upgraded version - Provided as seamless Geodatabase in ETRS89/LAEA1052 CRS - Madeira Islands, Switzerland, Iceland and Northern Ireland included - Sea buffer (25km) improved so they are consistent across all CLC layers - No-data buffer (code 999) outside of valid data area was deleted. Value 999 is acepted only for Andorra area - Small gaps identified in v1 were repaired - Remaining neigbouring polygons with the same code, as identified in v1, were resolved - Contains 38 countries

V1: 04/2010 - First release - provided as seamless Geodatabase in ETRS89/LAEA1052 CRS - contains 36 countries - Sea buffer (25km) introduced