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Woodcock, C.

Publications and source records attributed to Woodcock, C..

Nested-hierarchical scene models and image segmentation

An improved model of scenes for image analysis purposes, a nested-hierarchical approach which explicitly acknowledges multiple scales of objects or categories of objects, is presented. A multiple-pass, region-based segmentation algorithm improves the segmentation of images from scenes better modeled as a nested hierarchy. A multiple-pass approach allows slow and careful growth of regions while interregion distances are below a global threshold. Past the global threshold, a minimum region size parameter forces development of regions in areas of high local variance. Maximum and viable region size parameters limit the development of undesirably large regions. Application of the segmentation algorithm for forest stand delineation in TM imagery yields regions corresponding to identifiable features in the landscape. The use of a local variance, adaptive-window texture channel in conjunction with spectral bands improves the ability to define regions corresponding to sparsely stocked forest stands which have high internal variance.

Woodcock, C.

Variograms and spatial variation in remotely sensed images

Research is presented that is aimed at developing a link or connection between ground scenes and spatial variation in images. The link is established through the use of models of scenes and a measure of spatial variation - the variogram. The approach used to explore the nature of spatial variation in remotely sensed images can be thought of as a 'bottom up' approach because it starts with a model of the scene and works toward the characteristics of a remotely sensed image derived from the scene. To date, observed images at two resolutions for each of three kinds of environment have been used to evaluate the use of variograms in real images. The images are from forests, residential, and agricultural environments. One resolution used is 30 m from the Thematic Mapper or Thematic Mapper Simulator. For each environment also there is fine resolution data from the range of 0.15-2.5 m. It is noted that variograms from these images show considerable structure. Work continues on checking the validity of the disk model (a way of representing trees and their shadows).

Woodcock, C.