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Object extraction and revision by image analysis using existing geospatial data and knowledge

The paper focuses mainly on extraction of important topographic objects, like buildings and roads, that have received much attention the last decade. As primary input data, aerial imagery is considered, although other data, like from laser scanner and high resolution satellite imagery, can be also used. After a short review of recent image analysis trends, and strategy and overall system aspects of knowledge-based image analysis, the paper focuses on aspects of knowledge that can be used for object extraction: types of knowledge, problems in using existing knowledge, knowledge representation and management, current and possible use of knowledge, upgrading and augmenting of knowledge. Finally, an overview on commercial systems regarding automated object extraction and use of a priori knowledge is given. As some commercial systems on building extraction and 3D city modelling as well as advanced, practically oriented research have shown, in spite of the remaining problems, and need for further research and development, use of knowledge and semi-automation are the only viable alternative towards development of useful object extraction systems.