Progressive transmission of vector data based on changes accumulation model

The progressive transmission of map data over World Wide Web provides the users with a self-adaptive strategy to access remote data. It not only speeds up the web transfer but also offers an efficient navigation guide in information acquisition. The key technology in this transmission is the efficient multiple representation of spatial data and pre-organization on server site. This paper alms at offering a new model for the multiple representations of vector data, called changes accumulation model, which considers the spatial representation from one scale to another as an accumulation of the set of changes. The difference between two consecutive representations is recorded in a linear order and through gradually addition or subtraction of "change patches" the progressive transmission is realized. As an example, the progressive transmission of area features based on this model is investigated in the project. The model is built upon the hierarchical decomposition of polygon into series of convex hulls or bounding rectangles and the progressive transmission is accomplished through component of the decomposed elements.