OSGIS 2012, Nottingham Sandy Buchanan Project ManagerSlide 1 of ## <<Enter presentation title here>>
What is a Cartogram?car·to·gram/ˈ kärtəˌ gram/ A map on which statistical information is shown in diagrammatic form. A small diagram on the face of a map, showing quantitative information. An abstracted and simplified map the base of which is not true to scale.
Project Goals • To enable social scientists and others to create, share and reuse bespoke cartograms • The project will offer a production strength generic service and associated toolset. • It will alleviate the problems associated with production complexity and computational expense.Slide 6 of ## <<Enter presentation title here>>
Technology Being Used • Celery and RabbitMQ to manage the distributed task queue including the ability for multiple instances on multiple servers i.e. send it to the cloud if required • Using ScapeToad Cartogram generation. ScapeToad is a cross-platform, open-source application for producing cartograms. Its written in Java and uses the ESRI Shapefile format for input and output. • The algorithm used to compute the cartogram is based on the diﬀusion-based method for producing density equalizing maps by Michael T. Gastner and M. E. J. Newman
Outputs • The main output from the project is an API • The API is then used to service a website allowing non technical users to generate cartograms. • There is also a ‘widget’ allowing users to embed the basic website functionality in their own site. • The API, can of course, be used directly
The API • The API is accessed through the use of cURL commands or a REST Console/Client. These are available as add-ons for Chrome and Firefox web browsers. • Documentation and user guide available soon
The API• The API • Allow authenticated users to upload a validated, virus checked shapefile. • The shapefile can be ‘simplified’ to reduce computational time. • Select polygon layer to transform and the metric variable linked to that layer that will become the metric layer for the cartogram • Utilise the Gastner/Newman diffusion-based algorithm • Allow the computation to be farmed out to multiple servers if required for complex cartograms • Allow retrieval of new cartogram, shapefiles, distortion grid and metadata
The Website • Searchable gallery of user contributed cartograms • Cartogram generation interface • Multiple cartograms from a single shapefile • Output generation • Download • Access to ‘Widget’ Code • Access to API documentation • Further Cartogram resources