The book covers the principles, techniques, and standards for online GIS. This new edition covers the most recent major advances in the metadata arena. The semantic web (Web 2.0) is now well developed. GPS has also advanced in terms of the availability of Location-Based services, which rely on metadata and online services. In this new edition, all chapters are significantly revised and updated. New chapters are included to cover XML formats used in online GIS, SDI Metadata portals, Mobile GIS and Location-Based services.