1. http://cartogrammar.edina.ac.uk AIM & OBJECTIVES
The aim of the Cartogrammar project was to address two principal barriers to uptake and use of
cartograms by a wider social science audience:
(i) lack of an easy to use production facility and
(ii) inherent computational resource barriers.
These aims have been addressed by the creation of a robust, production level service through
the implementation of an API allowing the integration of on demand cartogram generation facility
which moves any necessary computational expense to the server end thus removing any client
side bottlenecks.
Recognising that the API itself is of limited utility to casual users, we have exploited the
development of the API and used it to drive the core functionality of the accompanying website,
gallery and widget. This site acts as an interface for non-specialists, providing the functionality to
generate and download bespoke cartograms and search and download cartograms from the user
contributed gallery.
The terms and conditions of use are based on an OpenDatabase Commons licensing framework
ensuring that through the gallery other social scientists can reap the benefits of the data created
by others.
End users can also generate html for embedding in their own website enabling them to generate
cartograms.
NON TECH SUMMARY
A cartogram is effectively a transformed map visualisation of data. The transformation is
usually based around some thematic mapping variable e.g. population or share of electoral vote.
The geometry or spatial configuration of the map is distorted in order to convey the information
of this alternate variable. The ultimate rationale behind re-projecting map data in this fashion is to
overcome the inherent bias traditional maps convey in as much that they tend to over-exaggerate
the importance of larger areas as opposed to smaller ones i.e. they give visual dominance to the
geographic area rather than the variable of interest under study.
The Cartogrammar project offers a production strength generic service and associated toolset
which breaks the two main barriers associated with production of cartograms i.e. complexity and
computational expense. This has been achieved through the development of:
• a Website
The website is available at cartogrammar.edina.ac.uk and provides an easy to use cartogram
generation interface for non-specialists to use. It also provides a searchable gallery of user con-
tributed cartograms for viewing and downloading.
• an API
The API is accessed through the use of the HTTP protocol and is employed as a RESTful web
service. The API documentation is available for download from the Cartogrammar website.
• an embeddable widget.
Users can also generate an html <iframe> code snippet allowing them to embed the cartogram
production capability on their own website.
ABOUT THE SITE
The Cartogrammar site is designed to assist in the production of Cartograms.
The website offers:
• A web based interface to capture the Cartogram generation parameters
• Cartogram production on EDINA compute infrastructure
• Cartogram delivery through the website Gallery
• Access to an API for direct interaction
• The ability to generate the HTML required to embed the production functionality within another website
The Cartogrammar API is based on ScapeToad1
which is a cross-platform, open-source application
written in Java, designed as an independent application using the ESRI Shapefile format for input and
output. It uses the Gastner/Newman [2004] diffusion-based algorithm to adapt map surfaces to user-
defined variables without altering their topological relations2
.
The project was supported by the ESRC and developed by EDINA at University of Edinburgh.
1 http://scapetoad.choros.ch/
2 http://www.pnas.org/content/101/20/7499.long
WHAT IS A CARTOGRAM?
A Cartogram may be defined variously as :
• A special type of map which attempts to convey a general sense of geography in addition to one or
more other important statistical elements.
• 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.
CARTOGRAM EXAMPLES