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MapQuery and SVG charts: a powerful interface for aggregated data
Steven Ottens, Geodan
Spatial data traditionally has been displayed using maps and tables. Maps, though good in showing the spatial extent, are not always optimal in showing (aggregated) geo-statistical data. The human mind can easily be tricked into believing that a bigger country has a bigger share of the pie. Tables show the individual records, but still lack the overview of aggregated data, also tables are notoriously hard to read.
To view the information in an aggregated form one has to build complex queries. These are often slow and do not scale well and the user either has to interpret the resulting map or compare numbers in a table. The first being not very precise the second not very intuitive.
Within EuroGeoSource, a cross European project that allows users to identify, access, use and reuse aggregated geographical information on geo energy and mineral resources, we have come up with a new way. The users are not typical GIS experts and do not have the knowledge to build custom spatial queries. Instead based on the user requirements we have determined the most important types of aggregation (eg. by country, by deposit-type etc).
The user can search for one or more commodities. Using MapQuery and gRaphael, an SVG chart library, we than present the aggregated information in interactive (pie) charts. He can use the charts as a selection method, for instance by clicking on a single country in the 'countries chart' he will see all the occurrences of the commodity in that country on the map.
The result is a fast and intuitive way to search for aggregated data. Providing overview on the distribution of data in multiple domains and still giving access to detailed data in a traditional GIS manner.
Steven Ottens has been involved in the foss4g community since 2005. Developing intuitive high performance webmapping applications and actively contributed to various OSGeo projects. Currently focussing on the UxDesign aspects of (web)GIS.