Date of Award

12-2003

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Spatial Information Science and Engineering

Advisor

Max J. Egenhofer

Second Committee Member

Michael F. Worboys

Third Committee Member

Werner Kuhn

Abstract

Sketching is a creative form of describing a spatial scene. People perceive such a scene in a straight forward way and build a mental model of the objects contained in a sketch. Whereas these objects might be regions, a sketch only contains lines and, therefore, developing automated sketch interpretation means outlining a rationale to grouping lines according to the objects they belong to. Automated sketch interpretation allows efficient processing of sketches. Labor intensive manual extraction could be brought to a minimum and, therefore, spatial data in form of sketches and spatial information extracted from sketches would be available more readily. Though spatial data in the form of sketches are less common than collected aerial photographs or satellite images, an automated sketch interpretation could provide valuable findings for researching feature extraction from imagery. This thesis outlines a perceptual sketch interpretation model that applies theories from spatial reasoning and gestalt theory. Gestalt theory provides laws of organization, which describe how people organize their visual input. The law of good continuity is incorporated into the sketch interpretation model. It is used to identify regions with a continuous boundary. The model first identifies a set of regions and then extracts the region with the most continuous boundary. Two alternative sets of regions can be used in the model: (I) the set of all possible regions of a sketch or (2) a subset containing regions with continuous boundaries. The latter is typically significantly smaller than the full set. This thesis outlines a perceptual sketch interpretation model. The assessment of perceptual sketch interpretation model shows that by applying the law of good continuity to identify regions, the correctness of the sketch interpretation is improved. The sketch interpretation process also executed much faster using a subset of regions than when using all possible regions.

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