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