MAPS ALIVE - VIEWING GEOSPATIAL INFORMATION ON THE WWW

We describe a WWW-based system - consisting of browsers, servers and c onnecting protocols - which allows users to view, search and post geog raphically-indexed information of the Earth. Much information availabl e on the WWW, such as weather reports, home pages of National Parks, V RML models of cities, home pages of Holiday Inn hotels, Yellow and Whi te Page directory listings or traffic and news reports, is better loca ted and visualized when displayed directly or via clickable anchors on top of 2D maps or in full 3D environments. We have developed two geog raphical browsers: a 2D map browser capable of continuous scroll and z oom of an arbitrarily large sheet and a 3D flight-simulator browser ca pable of continuous flight around the Earth. Both browsers download an d cache geographical information, geometrical models, and URL anchors in small regions called tiles. The tile caching process is based on th e user's current position, velocity, and acceleration in the 2D/3D spa ce as well as on the latency of server replies. A user can program the se browsers by adding small application programs - mapplets. On the se rver side, we have developed geographical and geometrical servers whic h contain very large data bases of images, elevations, lines, points a nd polygons stored in tiles structured into hierarchical pyramids or q uadtrees. We have also developed a metadata server which contains, in hierarchical layers, URL pointers and geographical coordinates of vari ous WWW documents, geographical information and geometrical models. (C ) 1997 Published by Elsevier Science B.V.