Abstract: Geospatial ontology development and semantic knowledge discovery addresses the need for modeling, analyzing and visualizing multimodal information, and is unique in offering integrated analytics that encompasses spatial, temporal and thematic dimensions of information and knowledge. The comprehensive ability to providing integrated analysis from multiple forms of information and use of explicit knowledge make this approach unique. This also involves specification of spatiotemporal thematic ontologies and populating such ontologies with high quality knowledge. Such ontologies form the basis for defining the meaning of important rela-tions and terms, such as near or surrounded-by, and enable computation of spatiotemporal the-matic proximity measures we define. The ability to automatically and semi-automatically extract metadata from heterogeneous, and multimodal data from diverse sources with unstructured, semi-structured and structured data, while exploiting relevant ontologies and associated knowl-edge bases, form the basis for analytics.