The use of ERTS imagery for estimating land-use land-cover is of particular importance for the Canadian Department of the Environment for many reasons, one of which is the fact that this Department is using a lands-wide data bank of river basins characteristics for interpolation of hydrologic information in which land-use land-cover is an important one. Initially data on land-use land-cover were obtained by abstracting them by hand from 1/200,000 topographic maps, and were limited to the following elements: forested area, lake covered areas, swamp covered areas, and urbanized areas. The roughness of the information thus obtained, together with the fact that the data obtained could not be updated, resulted in significant difficulties in using the data in the interpolation of hydrologic information. This is particularly true when the technique of interpolation was a spatially distributed hydrologic model, recently developed and applied with success where detailed information on land-use and land-cover was available.

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