Efficient Integration of Data Graphics into Virtual 3d Environments

Maps employing thematic map symbols, such as bar or pie charts are often used and constitute a standard method of displaying thematic data with geospatial reference. With the increasing popularity of virtual earth technologies, such as Google Earth, these methods of displaying thematic data are adopted for virtual 3D environments. The efficient creation of data graphics for the integration into virtual 3D environments calls for suitable data structures and processes. The research presented in this paper shows the development of a prototype for the generation of data graphics. The developed prototype is based on several existing technologies. The representation of the diagrams is described using a profile of DiaML (Diagram Markup Language) (Schnabel 2007). As geo data input format we devised a simple XML format. The formal diagram description in DiaML and the thematic data with spatial references are then transformed in one of three output formats (X3D, SVG and KML and COLLADA) depending on control parameters which are specified in a separate document. The different templates of the XSL transformation are kept as generic as possible to make them reusable for different diagram types and output formats. The prototype has successfully been tested with different sets of uniand multi-dimensional data. Introduction Thematic maps employing 2D data graphics or thematic map symbols, such as bar or pie charts, for the display of statistical data or other abstract data values are often used and constitute a standard method of displaying thematic data with geospatial reference. With the increasing popularity of virtual earth technologies, such as Google Earth or Bing Maps 3D, these methods of displaying thematic data are adopted for virtual 3D environments (e.g. Sgrillo 2009 or Sandvik 2009). We believe that the visual combination of data graphics with the quite naturally perceived virtual 3D landscape, in which the data was collected in, is a valuable complement to traditional 2D representations. Ongoing research (Bleisch et al. 2008) evaluates the appropriateness of such a combination in different experimental and applied settings. The goal of the research presented in this paper is to define suitable data structures and processes for an efficient creation of data graphics for the integration into virtual 3D environments. The processes need to be flexible enough to be adaptable to different text-based 3D display formats and standards, data and diagram types. This paper presents the development of a prototype that fulfils the above mentioned requirements. It illustrates the difficulties and the developed solution and presents the results from evaluating the prototype with different data sets, 3D display formats and diagram types. Concepts and formats The diagram generation prototype is developed based on several existing technologies. The core of the prototype is a XSL (eXtensible Stylesheet Language) transformation combining the thematic geo data which is to be displayed with the formal description of the diagrams (Figure 1). The output of the transformation process is one of three different 3D display formats. Figure 1. Overview diagram generation workflow The input geo data and its associated attribute values need to be available in a generic format. We devised a simple XML (eXtensible Markup Language) format as input of the transformation process. A number of XML elements allow the description of the input geo data such as a spatial point reference for each data set, the attribute values and their description (Figure 2). The XML format is described using XMLSchema which allows validation of created input files. Using an XML format for the description of the input data has several advantages, for example, it is a text based format and easily generated out of most databases or other storage forms of existing geo data. ... ... ... ... ... ...