Incorporating remotely sensed data into a GIS: The problem of classification evaluation

Gathering information from remotely sensed data for input to geographical information systems is a relatively common practice. In situations where the remotely sensed data are used indirectly and it is a thematic classification of the data which is incorporated into the system care is required in assessing its quality. Evaluating the classification in relation to a pre‐defined threshold accuracy can be unreliable since classification accuracy is a spatially variable phenomenon. In constructing a GIS it could be possible to include erroneously an unsuitable classification. Conversely a suitable classification could be excluded. Users of thematic classifications derived from remotely sensed data therefore need to be aware of the magnitude and spatial distribution of classification accuracy for its optimal use in the system.