Spatial Reasoning in Remotely Sensed Data

Photointerpreters employ a variety of implicit spatial models to provide interpretations from remotely sensed aerial or satellite imagery. The process of making the implicit models explicit and the subsequent use of explicit models in computer processing is difficult. In this paper one application is illustrated: how ridges and valleys can be automatically interpreted from LANDSAT imagery of a mountainous area and how a relative elevation terrain model can be constructed from this interpretation. It is shown how an illumination model is being used to explain many of the features of a LANDSAT image. Finally, it is shown how to examine valleys for the possible presence of streams or rivers and it is shown how a spatial relational model can be set up to make a final interpretation of the river drainage network.