Electronic multimedia choropleth maps design through SVG.

Karel Stanek, Lucie Friedmannova

Laboratory on Geoinformaics and Cartography, Dept. Of Geography, Masaryk Univerzity in Brno

Kotlarska 2, 611 37 Brno, Czech republic


Paper is focused on usage SVG as multimedia format for creation of electronic thematic maps. We already use SVG format for publishing vector on WWW, by this way we use SVG only such graphic format which is easy generate by CGI scripts. In this paper we would like to describe our experience with SVG such complete environment, client side or non-web , for electronic map design. Possibility of internal scripting enable possibility to use SVG such data storage, visualization tool and simple geoprocessing. Of course this role cannot play SVG self but in collaboration with appropriate interpreter supporting SVG DOM and with another standard www tools such like a JavaScript.

We will focused on thematic mapping, exactly of choropleth map design issues. Key point which we solved are implementation of cartographic zoom (scale driven map face, it means automated and semi generalization of visualized features), variable text placement (different text density with alternative based on on-focus text boxes), map face driven legend, floating and rotatable map face, displaying of additional attributes in table and graph form and attaching multimedia features with on-focus appearance. Special attention will devoted to variable color management of map face (scale or theme driven with possibility of limited user control). Also cartometric issues and statistics of map feature are discussed. Beside cartographic issues we would like to describe creation of controls in SVG and possibility for user interaction.

Electronic choropleth maps will demonstrated on two different types land divisions. First will based on demographic data with fixed hierarchy of choropleth cells defined by administrative units. Second case will based on biogeographic data with dynamic scale driven cell coverage. Area visualized in both cases is island map of region South Moravia.

Majority of features proposed for choropleth map design are organized in reusable code blocks. But according to specifity of unique visualization rules we will present more ad-hoc solutions then regular framework. Possibility of definition of such framework will be discussed in paper.

We will discuss also our experience with preparation of geographic data for SVG publication on all track from standard geodatabase over generalization purpose preprocessing to coordinate system translation. Routines for different types of GIS environment (ArcView 3.x, Geoconcept, ARGO) will presented.

Major client platform used for our development was Adobe SVGviewer running under Microsoft Explorer browser, nowadays we collect experiences with usage Adobe SVGviewer on Mozilla.