Gridded Population Cartograms - What is it all about?
As a visitor of the Worldmapper website you might already have got an insight to the things we are doing and the techniques we are using to create our maps. If not, you should read our 'About' page to get the basics of this project. This page that you are reading here gives you some more information about a slightly different approach that we started adding to Worldmapper in 2009. All maps have been created by Benjamin Hennig as part of his PhD research on Worldmapping beyond mere descriptionGridded Population Cartograms
The Worldmapper cartograms try to create a different view on the social image of our planet by putting a specific variable of interest in the centre of the depiction. Although these cartograms try to preserve the unique shape, this might cause difficultiesinterpreting these depictions in more detail. Statements on the conditions of the topic under scrutiny of each country can only be made on a global scale but not on a regional or national level. The advantage of preserving the shapes can thus turn into a disadvantage.
The creation of grid-based cartograms can be one solution to this problem. Instead of a single value per country a much higher number of values based on an equally distributed grid is taken as a basis for the cartogram creation. The resulting cartograms thus give a much more detailed impression of the interal variation of the specific topic even within countries or regions. More details on the methodological background can be found in the paper from the GISRUK 2009 conference (pdf) and in the proceedings from the 2009 ESRI User Conference.
The grid-based cartograms depict the population distribution in most of the territories shown in the other Worldmapper cartograms. Each cartogram shows a country or territory with an accentuation of its internal population variation. Depending on their size, some smaller territories or countries may be combined with others.
More populated areas appear more inflated while sparsely populated areas diminish. The conservation of the deformed grid as well as an underlying map of the original geographical extent help in the interpretation of each cartogram. To aid further orientation we labelled particular agglomerations. As some agglomerations are formed by several cities, we generally picked the largest of these cities to label the area. In addition, some minor cities might be labelled. This is the case for cities of trans-regional relevance (e.g. Belfast in the United Kindom) and on cartograms where some striking areas remain unlabelled when taking the largest agglomerations in the country. The number of cities labelled in each cartogram varies according to the specific layout of a cartogram: More cities are labelled the more striking agglomerations appear to be in a cartogram.
The largest obstacle in the creation of grid-based cartograms in the compilation of suitable datasets. Socio-economic indicators usually are not surveyed on a grid basis but on administrative levels which sometimes can be quite large in their extent. This makes data creation for such a method a challening issue.
For the population cartograms we used data from the Gridded Population of the World, version 3 (GPWv3) of the Socioeconomic Data and Applications Center (SEDAC) produced by the Center for International Earth Science Information Network (CIESIN) of the Earth Institute at Columbia University. The data and further information on the methods used to estimate these data are presented on the SEDAC website. Our paper from the GISRUK conference tells you more about the way we utilised the data for our intended use.
Information on the largest cities and agglomerations for each country were taken from the GeoNames database. For each city we used the internationally common names rather than the locally common names.
Hi-resolution images of the country cartograms are currently only available on request.
Feel free to submit us your thoughts and comments on our cartograms and any suggestions for our further work.
For information on how to get in touch with us, go to the 'Contact' page.
This work has been funded by the Leverhulme Trust.
Further support has been provided by Data East, LLC who provided a license of XTools Pro for ArcGIS.
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