Sandy BuchananProject Manager
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OSGIS 2012, Nottingham
What is a Cartogram?
car·to·gram/ kärtə gramˈ ˌ /
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.
Funded ByESRC
Developed BYEDINA
Example
Traditional Map with shading
Cartogram – Area proportional to cases
Example
Local Authority GCSE performance
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Project Goals
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• 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.
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 di usion-based method for ffproducing density equalizing maps by Michael T. Gastner and M. E. J. Newman
Technology Solution
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
Website
Job Management Screen
Shapefile and Metadata
Creation Parameters
Cartogram View and Download
Generate Widget Code
Embedded Widget
Progress
• API is complete
• Website is complete and about to be moved onto production (a few workflow tweaks needed)
• Widget works
• Looking for volunteer testers