Browsing by Author "Elliott, David B."

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    The application of an illumination model to a mountainous LANDSAT scene
    Elliott, David B. (Virginia Polytechnic Institute and State University, 1982)
    The multispectral scanners (MSS) of the LANDSAT satellites collect solar radiation of different wavelengths reflected from the earth's surface. While the different greytone values of a given band of a LANDSAT image of simple terrain are due almost entirely to the various reflectivity values of the features of the earth's surface (such as vegetation, mineral deposits, or bodies of water), the same is not true of areas of complex topography. In mountainous areas, the mixture of light and dark regions in a LANDSAT image may be due to shadow effects as well as the reflectivity values for those wavelengths of light of the various surface features. In this research, an illumination model is developed to help understand features observed in a LANDSAT scene of a mountainous area. The illumination model is defined and its implementation in the GIPSY (General Image Processing System) system is discussed. The application of the model to a particular LANDSAT scene is described including the development of an elevation model from the LANDSAT data. Finally, the illumination model image is compared with the LANDSAT scene and the results are discussed.
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    Spatial Reasoning in Remotely Sensed Data
    Wang, Shyuan; Elliott, David B.; Campbell, James B. Jr.; Ehrich, Roger W.; Haralick, Robert M. (Department of Computer Science, Virginia Polytechnic Institute & State University, 1981)
    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.