SVG web mapping: Four-dimensional visualization of time- and geobased data

Abstract

A tool to generate a vector based visualization of geographic information has been developed at the University of Osnabrück. The web mapping application uses SVG and implements some interaction functionalities. In addition, the application can be used to visualize further georeferenced information, such as weather or traffic data. By using vector graphics it is possible to zoom into a region without loss of precision. If necessary, details can be inserted without loading the whole dataset, as would be required in a pixel-based approach. The application offers the possibility to navigate inside the map (two dimensions), zoom, to select additional georeferenced data (one dimension) and to look at different points in time (one dimension). The user is able to interactively observe a geographic chart and to add further georeferenced information. Thus it is possible to interactively control the amount of visualized data and the character of the visualization. Moreover it is possible to execute an animation of the time steps automatically. By combining different maps with other georeferenced data and animating it the application results in a very flexible tool and the observer can easier understand four-dimensional georeferenced data. The only requirement is an SVG enabled web browser. The tool to generate the application is written in Java and generates all necessary SVG files and scripts, which will be placed on a server with PHP5. Therefor, some algorithms for processing the data and clipping are implemented. Up to now ESRI Shapefiles have been used as input. The geographic shapes are described in vector coordinates so it is easy to convert the data into SVG. Also raster formats can be included, for example GRIB Files are supported as input for weather data. In this case some algorithms to vectorize the data are applied before creating SVG graphics. In a current project the program is enhanced and XML-Files with traffic data are processed. Examples for some SVG Web Mapping applications are available at http://www.inf.uos.de/svgopen2008.