Ever Wondered How Virtual Earth Displays Large Mapping Data Sets in the Browser?

Have you ever wondered how Microsoft's Virtual Earth manages to display extremely large mapping data sets in the browser almost instantaneously? Well, if this is indeed the case, then, the Tiled Vectors demo might clue you in on the matter at hand. The Tiled Vectors demo is now available for download and, of course, it is a product of Microsoft Research. The demonstration comes to illustrate a technique designed to display enormous data sets as vectors in client-side map browsers. This is possible because all the vectors are actually tiled into files of constant size.

"The demo shows a way to solve the problem of showing extremely large mapping data sets in the web browser. If you have used the Virtual Earth AJAX/JavaScript Map Control or other web-based mapping controls or any web application with a large number of DOM elements/SVG/VML graphics, then you probably have seen that loading extremely large data sets (with thousands of points, lines, and polygons) can bring the browser to a crawl because of limitations in the browser DOM," revealed Keith Kinnan, Software Development Engineer Microsoft Virtual Earth / Live Search Maps.

Without a technique such as Tiled Vectors, the browser would simply become non-functional as it would struggle to process the vast amounts of JavaScrip points. Tiled Vectors makes sure that the browser only manages and displays as much data as necessary for a single screen. The technique involves a bit of pre-processing of the data by an offline preprocessor. All the information is segmented into tiles before it goes to the browser.

"Since the data is broken into constant-sized sets, the original data set can be arbitrarily large - so the solution scales really well to extremely large data sets. Regardless of which level of detail you are viewing the map from, the amount of data the map loads is always constant. This significantly improves performance. The vector data is still loaded using Virtual Earth VEShapeLayers in JavaScript - so the shapes are still interactive and can be controlled from client code and respond to events," Kinnan added.