Metodyczne i realizacyjne aspekty aktualizacji bazy Corine Land Cover

Zgodnie z zaleceniami Europejskiej Agencji Środowiska co dziesięć lat powinna być aktualizowana baza danych odnoszącą się do pokrycia terenu. Ponieważ pierwsza baza danych zawierała informacje o pokryciu terenu na obszarze Europy Zachodniej i Środkowej w 1990 r., tak więc w 2000 r. należało przystąpić do jej aktualizacji. W artykule przedstawiono zagadnienia korekty starej bazy danych oraz sposobu jej aktualizacji. Poprzez porównanie zawartości obu baz określono zmiany pokrycia terenu, jakie zaszły na obszarze Polski w ostatniej dekadzie XX w.

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There are presently numerous international programmes aiming at acquisition of information on land use and land cover. The folIowing programs can be mentioned: Global Terrestrial Observing System (GTOS), International Geosphere-Biosphere Programme (IGBP), Pan-European Land Use and Land Cover Monitoring (PELCOM) or UE CORINE Land Cover (CLC). At the beginning of nineties database containing information on land cover in Europe was prepared within CLC programme. According to assumptions of this programme the database is to be updated in 10-year's cycle. So, in the beginning of 21 st century this database started to be updated. As a result of its revision CLC-2000 database, as well as database of land cover changes 1990-2000 were prepared. Landsat satellite images collected at the tum of 20th century were used as a source material for CLC90 updating. In 2002 Poland joined programme of CORINE Land Cover database revision; execution of this work was granted to the Institute of Geodesy and Cartography. Criteria of preparation of new database (CLC-2000) have not been changed, comparing to previous database, but new method of preparation, based on visual interpretation of images displayed on monitor screen, was applied. Methodology of CLC-90 revision assumed first of all correction of database prepared in nineties. This correction was aimed at uniforming database at European level and at ensuring its consistency. It concerned correctness of identification of particular land cover forms (compatibility to the modified legend), precision of location of polygon boundaries and formal conformabilities related to topology and data formats. Correction of CLC-90 database was made on the basis of images taken in nineties, which were transformed to "1992" coordinate system. New satellite images were also transformed to this system. According to methodology of database revision only these land cover changes were entered to new database, which had area larger than 5 ha (in case of change of land cover extent) or 25 ha (if new form of land cover appeared). Comparison of databases containing land cover information from 1990 (CLC 90) and from 2000 (CLC 2000) enabled to detect changes which occurred in the last decade of 20 th century. In most cases these changes appeared to be slight. In total they covered area of about 2500 km2, i.e. only 0.80 % of Poland's territory. There are also the other products within CORINE Land Cover programme like satellite orthophotomaps, mosaics covering particular countries and the whole Europe, as well as raster and vector land cover databases with various spatial resolutions. The Institute of Geodesy and also prepared the map presenting distribution of all 31 land cover forms, in Poland. This map was published at the scale of 1:1 000 000 in a limited number of copies.