Generating Focus Maps Using Open Standards
Digital maps in the world wide web are mostly intended for a large user base with a multitude of individual viewing patterns and cultural imprints. Because most digital maps are static in design, they hinder users in obtaining information that is relevant to her individual purpose.
One approach to make map-design more effective are focus maps. By nesting regions with gradually increasing accentuation, the perception of the user can be guided to relevant regions. Emphasis can be achieved by cartographic design scopes, like for instance color highlighting or symbolic exemption.
This research is devoted to the development of a proof-of-concept implementation of an open-source focus map generation tool using open standards, exploiting available computational resources and user context information to create adaptive and task-specific digital maps.
Further the concept of focus maps is enhanced: By differentiating the relevance on the object level, a more fine-grained distinction between different aspects of the user's interests can be reflected and a smother focus effect achieved.
Additionally the implementation supports accentuation of not only graphical, but also textual symbols.
At first, the relevance of every object to be displayed is estimated primarily by it's distance to objects, where the relevance to the user is already known.
Second, a salience-value is calculated based on the relevance of the objects and the user's design preferences. The salience represents the adoption of the object's relevance for visual representation with respect to the user's viewing pattern.
Third, with the calculated individual salience information a Styled Layer Descriptor file (SLD) containing the styling information for the focus map is generated by adding styling rules to a given base SLD file. The modified SLD file can than be used by any regular renderer application that supports the SLD specification.
The underlying OpenStreetMap data is obtained from a Web Feature Service (WFS).
Figure 1: Relevance estimation, based on distances of the town center of Bonn (upper right) and suburb Poppelsdorf (lower left). The darker the green, the more relevant the object is.
Figure 2: Workflow Focus Map Generation
Focus Map Applet
An applet was implemented, demonstrating the core concepts of the map generation process.
The map data ist based on OpenStreetMap. Ids and Attributes refer to OpenStreetMap.
Click HERE to launch the applet. ATTENTION: The applet (size about ~6.5mb) takes quite a lot of computational resources!
Julian Hagenauer (julian.hagenauer atsign geog.uni-heidelberg.de)
Department of Geography, University of Heidelberg