51 Web-based Spatio-Temporal Presentation and Analysis of Thematic Maps Hans Voss, Natalia Andrienko, Gennady Andrienko, Peter Gatalsky Abstract Map-based visualization and analysis will become an important factor in future Web- applications. Regional location atlases and logistics support are prominent examples. Location-based services will likely become a killer application of next generation mobile phone computers using, e.g., UMTS technology. In the paper we introduce our Descartes system as an interactive, direct manipulation Web-Map software. Descartes is specifically designed to support thematic mapping by automatically proposing alternative visualizations of geo-referenced statistical variables and by providing many functions for analysis. By examples, the paper sketches some of the newer functions built for mapping of spatio-temporal data. Hans Voss, Natalia Andrienko, Gennady Andrienko, Peter Gatalsky German National Research Institute for Information Technology - GMD D-53754 Schloss Birlinghoven Fax:+49 2241 142889 e-mail: hans.voss@gmd.de