Tirol Atlas - an SVG based online Atlas Information System

Klaus Förster & André M. Winter.
Department of Geography, University of Innsbruck, Austria, Europe

Keywords: webmapping, geometry database, thematic database, javascript, interface, atlas, information system.

The Tirol Atlas aims to build an online Atlas Information System for the regions of Tirol (Austria) and South-Tirol (Italy), providing geographical knowledge with a scientific background relevant for planning and everyday life. Spatial information is displayed in a modern and innovative way using open standards like Linux, PostgreSQL, Perl, HTML and last but not least SVG.

Where do we use SVG

a) Thematic Maps

The first field of SVG usage is the creation of thematic maps. Right now there are about 120 maps available online dealing with population and tourism. Visualization is realized by a Javascript object (Map_Thematic.js) that "knows" how to color areas, draw circles, piecharts, barcharts, legends and output metadata.

An intranet application written in Perl allows editors to create maps choosing variables from a PostgreSQL database, set formulas, colors, thresholds, scales and legend features. Each map is made up by one or more map layers (e.g. colored areas with circles on top) and can be assigned to a menu that appears as dropdownlist within the interface. All definitions are stored in the database, queried when the user selects a specific topic and translated to data objects and function calls that correspond to methods in the Map_Thematic visualization object.

Latest addition to the map creation system is a possibility to attach event listeners to single map layers triggering scripts that perform tasks like displaying graphs or additional datasets in external windows.

b) Topographic Maps

One of the current main tasks is the creation of a topographical map in UTM WGS84 projection at a scale of about 1:100.000. The first prototype contains layers for rivers, lakes, forests, peaks, streets, borders and villages. ESRI shapefiles with object id, type, level and name are imported into a point-, line- or polygon table within the PostgreSQL/PostGIS database according to their feature type. These tables are then queried by a Perl script using community ID or arbitrary x-y location to determine the desired extent. A PostGIS function translates lines and polygons into SVG path data during the query process. Map features are grouped according to their type that corresponds to a central stylesheet and written out using their level item as stacking order.

A pre generated set of regular 10x10km SVG slices allows panning through the whole region using getURL for loading geometry according to the current viewport.

c) Interface & Navigation

The rich feature set of SVG allows realization of a user friendly map interface through:

All necessary tasks are implemented with JavaScript on the client side using the browser's scripting engine. Zoom & pan of the overview and main map is controlled by this central script as well as the current state of the content menu and legend window. Keeping the main map static in a frame helps to reduce data traffic.

Due to constraints in viewer implementation and the fact that SVG is (not yet) perfectly suited as mapping format, a lot of script code represents workarounds that could be omitted as soon as SVG implementation enhances. Viewbox issues and lack of browser to plugin communication in "modern" browsers like mozilla and netscape strike the most.

Where else do we use SVG

.. well, there are a lot of other areas where we use SVG. In the "places section" where each community is briefly described with text & picture, an SVG overview map showing a dynamic marker reflects the current position. On click a spatial query is sent to the database that returns villages located within 15 kilometers ordered by distance. A prototype for an interactive population pyramid has been tested as well as a rudimental application to generate barcharts (1, 2) from the database. In preparation of the childrens & youth corner that will be established within the next year a configurable Memory Game with "didactical background" and a simple Puzzle have been realized.

Authors

Klaus Förster works for the Tirol Atlas in the fields of application programming, database and server administration. André M. Winter created the first attempt of an SVG-Atlas in the middle of 2000 at the University of Vienna. After one year in the multimedia and CD production branch at Freytag & Berndt Vienna he again returned to an SVG-project and is now member of the editorial staff of the Tirol Atlas.


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