Mapping uncertainty in land cover characterization by comparison of land cover cartographies - A case study for Portugal

Vasco B. Nunes and Mário Caetano
Remote Sensing Unit
Portuguese Geographic Institute (IGP), Lisbon, Portugal
Tel.: + 0351 21 381 96 00
Vasco.nunes@igeo.pt; Mario.caetano@igeo.pt

Abstract
In this paper we propose a methodology to assess uncertainty of land cover cartographies and its spatial distribution within a ranged scale. The method consists in overlaying different land cover databases and determining the uncertainty  values for the intersecting areas. This assessment is based on different nomenclature hierarchic level comparison and on the number of cartographies in agreement, assuming that different sources of information in agreement provide a higher level of confidence than the same sources in disagreement. A case study was developed for the mainland territory of Portugal. The selected spatial information databases had very different technical specifications, and therefore they had to be made comparable by some harmonisation procedures. The results are consequently, all directly dependent on these procedures. The universe of analysis was dramatically reduced and the overall agreement between all the applied cartographies was considered low at the highest class detail. However, it can be assumed that the resulting areas are now represented with a known level of uncertainty concerning land cover characterization.

Keywords: land cover, error, uncertainty, map comparison

In: Caetano, M. and Painho, M. (eds). Proceedings of the 7th International Symposium on Spatial Accuracy Assessment in Natural Resources and Environmental Sciences, 5 – 7 July 2006, Lisboa, Instituto Geográfico Português

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