Web mapping with Google maps Mashups: Overlaying Geodata

The term mashup is used for incorporating different web resources and information within a web site. Mashups are an integral part of Web2.0, which represents a variety of innovative resources, and ways of interacting with, or combining web content. Mashups are based on Application Programming Interfaces (APIs) that are online libraries of functions. Most of the APIs are available at no cost to web developers. Most common mashup applications involve web mapping or web cartography. There is a variety of API providers for map mashups, including Google, Yahoo and etc. The functionality of their APIs are similar, but the data content. Google provides a huge amount of geodata worldwide. With Google Maps API, web site developers can add dynamic maps to their pages, and can overlay their own point, line and polygon data on to the maps. Such data can be overlaid within the JavaScript code, from external XML or KML files. It is also possible to connect a database and overlay data from the database based on a query. In this study the basics for creating map mashups are introduced, then the ways of overlaying data are discussed and the usage of XML and KML files are focused on. KML overlays are not flexible and there are some limitations. XML overlays are more flexible, but there is no standard XML schema. Web developers can define their own elements and attributes, and develop their Javascript code accordingly. We propose an XML schema, which is full compatible with Google Maps API classes.