Indexing and Browsing Digital Maps with Intelligent Thumbnails

With the increasing number of digital maps and other geo-referenced data that are available over the Internet, there is a growing need for access to techniques that allow us to preview the content and to evaluate it relative to the requirements for complex spatial and thematic queries. . Analogous to the digital indices for fulltext searches on text documents, we introduce highly condensed, machinereadable indices of digital maps. The purpose of these “intelligent thumbnails” is to support sophisticated queries of the type concept@location. An intelligent thumbnail is based on a projection of the thematic content of a digital map onto a standard reference tessellation. To make the thumbnail exchangeable in a distributed and heterogeneous environment, the underlying Standard Reference Tessellation (SRT) is qualitatively abstracted from a polygonal representation to a connection graph. In combination with a hierarchical place name structure and concept ontology, it is used to evaluate the spatial and thematic relevance of the indexed data sources with respect to spatio-thematic queries.