ABSTRACT
The CLC2000 data layer is the product of the IMAGE and CLC2000 Project managed by the European Environment Agency (EEA) and the Joint Research Centre (JRC). The time consistency of applied satellite images was 2000 ± 1 year, hence much better than for the images used in CLC1990 (Feranec et al., 2012). The computer-assisted photointerpretation (CAPI) method, its variants A-updating of the revised CLC1990 vector layer on the basis of satellite images from 2000 ± 1 year (changes are derived by overlaying the revised CLC1990 and CLC2000) or B-computer derivation of CLC2000 layer on the basis of CLC1990-2000 changes identified by interpretation of satellite images coupled with the revised CLC1990 data layer (see Sections 5.4 and 5.6 in Chapter 5). Before the CAPI method could be applied the original CLC1990 was converted into digital format. With the help of the CAPI, methodological errors caused by drawing on transparencies during the production of CLC1990 were eliminated. Polynomial transformation or rubber-sheeting was used to eliminate the bulk geometric distortion. Residual geometric errors exceeding 100 m and coding mistakes were removed by editing (Büttner, 2014: 59). Data were also revised and generalized by removing the areas smaller than 25 ha. A copy of this revised CLC1990 was the basis for the CLC2000 data layer. The production time for CLC2000 data was reduced compared to the previous data layer from 10 to 4 years. All CLC1990 and CLC2000 data are today freely accessible from the EEA to any person or legal entity (Büttner, 2014). Geometric accuracy of used satellite images improved to ≤25 m. Likewise, the geometric accuracy of CLC data is better than 100 m and the thematic accuracy is ≥85%. The size of the smallest identified area (minimum mapping unit [MMU]) and its width (25 ha and 100 m; see Table 2.1 in Chapter 2) remained unchanged compared to the CLC1990 layer.
