SVG-BASED VISUALIZATION OF GEODATA QUALITY. TAKING THE KAKAMEGA-NANDI FOREST AREA AS EXAMPLE

K. Huth¹, O. Schnabel², G. Schaab¹

1 - Karlsruhe University of Applied Sciences, Faculty of Geomatics, Karlsruhe, Germany

2 - ETH Zurich, Institute of Cartography, Zurich, Switzerland

gertrud.schaab@hs-karlsruhe.de

Subproject E02 funded by the German Federal Ministry of Education and Research (BMBF) within the BIOTA East Africa project frame considers the analysis of longer-term forest cover changes in East African rainforests as one of its major tasks. Here, data sources range from satellite imagery and historical aerial photography via old topographic maps, official governmental records and forestry maps to oral testimonies by the local population and place names giving evidence for much earlier forest extents.

An analysis of such information will lead to a detailed picture of the forest use history over the last 100 years. This can be more accurate, i.e. more insights are expected, if the numerous data layers can be directly compared via their spatial reference as it is possible by means of a geographic information system (GIS). However, in a GIS the visualization in connection with a text which is already summarizing first results by pointing out locations is not feasible. The visualizing of the varied information together with a text inhabiting hyperlinks while at the same time illustrating differences in geodata quality will not only offer the opportunity to the scientist to gain new conclusions, but can be of use to a wider audience: for plain documentation, for presenting the results as well as for the individual working with the gathered data and information by anyone interested.

Therefore, the aim has been to develop a visualization tool for an integrated examination of a scientific paper on forest use in the considered area, the complete geodata gathered and its quality parameters. Hereby, for a start the implementation of a prototype is sufficient. Nevertheless, for conceptualizing the tool almost 100 geodatasets covering the Kakamega-Nandi forest complex in Western Kenya need to be taken into account. The programming applies scalable vector graphics (SVG) for displaying graphics and JavaScript for the interactive features.

The presentation will give background information on other studies aiming at illustrating geodata quality. Subsequently evolved designs for diagrams exposing the quality of the different geodatasets are introduced and judged against each other. The overall concept of the prototype implementation is discussed as well as finally its features demonstrated. The presentation will end with lessons learned by setting-up such a tool.