Distributed geospatial data access on the WWW.

摘要

This thesis investigates the design and implementation of a Web-based distributed geospatial data warehouse (WDGSDW) system which allows a user to query geographical information and access the geospatial data services across multiple servers over the Internet.; A multi-tiered client/server architecture was used to implement WDGSDW. The CORBA-based (for Java and C++), Java RMI-based and Java servlet-based implementations of the server-side components of DWGSDW are tested and compared for the contextual data service, which providing the user interface of WDGSDW. The search engine, which is the kernel of WDGSDW, supports combined text search and geographical search with an adjustable match factor.; WDGSDW system was tested using test data sets containing 6979 CEONet metadata files, 1690 CLI vector data sets and 45 CCRS raster data sets. For the contextual data server, CORBA and RMI techniques are 2 to 2.5 time slower compared to the Java servlet and a performance of 85 bytes/ms was observed for the latter, on average. The keyword searches can take up to 4.9 seconds compared to bounding box searches times of less than 2.5 seconds on a catalogue containing 8188 entries. (Abstract shortened by UMI.)