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Consistency in land‐cover mapping: Influence of field workers, spatial scale and classification system

Ullerud, Heidrun A., Bryn, Anders, Halvorsen, Rune, Hemsing, Lars Østbye
Applied vegetation science 2018 v.21 no.2 pp. 278-288
ecosystems, land cover, Norway
QUESTIONS: Land‐cover maps are used for nature management, but can they be trusted? This study addresses three questions: (1) what is the magnitude of between field worker inconsistencies in land‐cover maps and what may cause such inconsistencies; (2) in which ways and to what extent do spatial scale and mapping system influence inconsistencies between maps; and (3) are some biomes mapped more consistently than others, and if so, why? LOCATION: Gravfjellet, Øystre Slidre municipality, southern Norway. METHODS: Two different mapping systems, designed for mapping at different spatial scales, were used for parallel mapping by three different field workers, giving a total of six maps for the study area. Spatial consistency of the resulting maps was compared at two hierarchical levels for both systems. RESULTS: The average pair‐wise spatial consistency at the highest hierarchical level was 83% for both systems, while the average pair‐wise spatial consistency at the lowest hierarchical level was 60.3% for the coarse system and 43.8% for the detailed system. Inconsistencies between maps were partly caused by the use of different land‐cover units and partly by spatial displacement. CONCLUSIONS: Field workers made different maps despite using the same mapping systems, materials and methods. The differences were larger at lower hierarchical levels in the mapping systems and increased strongly with system complexity. Consistency among field workers should be estimated as a standard quality indicator in all field‐based mapping programmes.