Validating large‐area land cover databases with Maplets

Point sampling methods traditionally used for assessing accuracy of small‐area thematic maps are less suitable for large‐area, lower resolution maps. Maplets, or detailed maps of small areas, are proposed here as an alternative source of independent reference data for accuracy assessment. As a land cover census instead of a sparse sample of points, maplets can provide information on the composition, heterogeneity, and accuracy of individual map units, on boundary locational accuracy, and the spatial pattern of errors in the large‐area map. The technique is illustrated by a case study for a wildlife habitat map of southern California, USA. Overall agreement between the maplet and the large‐are map was 63%. However, the total area of map units in which the label agreed with the majority maplet class was 84%. This result suggests that much of the “error”; was actually generalization rather than misclassification.