Exploring Data Using Cartograms within ArcGIS Desktop

Cartograms, because they distort our normal view of things, are wonderfully rich research and teaching tools. A distance cartogram shows relative travel times and directions within a network. An area cartogram is a map in which some variable is used instead of the land area in each polygon to compute the size of that polygon. Many of us remember using graph paper to make rectangular area cartograms as undergraduates (but perhaps I am dating myself). Today, one can use Web GIS and desktop GIS to create cartograms. For example, nearly 700 variables can be mapped on www.worldmapper.org, and the data can be downloaded as Excel spreadsheets and analyzed within ArcGIS.

To dig deeper and make your own cartograms, with the ability to do bivariate analysis within a GIS environment, use the ArcScript cartogram tool that Tom Gross in the ESRI Applications Prototype Lab created, on: http://arcscripts.esri.com/details.asp?dbid=15638. How can a GIS, which focuses on the accurate spatial representations of features, be used to create cartograms? Try this script and find out!

Once you install the cartogram tool, inside ArcMap, access ArcToolbox. Create a toolset, add the cartogram tool, and run it. The intuitive interface allows specifying input and output, and even comes with a nice assortment of international population and other variables to practice on. You can distort the base layers so that your cartogram can include the distorted layers for reference. I did this for cities, a 30-degree world grid, and a satellite image of the Earth to see these reference layers overlaid on my cartogram.

In this example, I chose to map the total CO2 emissions by country in 2004, in millions of metric tons, from the US Energy Information Agency. What patterns do you notice?



The cartogram map layer has to be written into a geodatabase, but otherwise, the tool has few restrictions. I am very pleased cartographically with the results, and the methodology of how the cartograms are generated is well documented.

What other variables and scales could you map and analyze as cartograms?

-Joseph Kerski, ESRI Education Manager

Tom Baker

About Tom Baker

Tom Baker is an Esri Education Manager, specializing in STEM (science, technology, engineering, and math) education, teacher education, and educational research. He regularly publishes and presents on geospatial technologies across education.
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10 Comments

  1. blackpoll says:

    Can you provide more details on installation of this tool? Thank you.

    -m

  2. jjkerski says:

    M: Access the cartogram script page. Save the tool as a zip file. Unzip the zip file into a folder. Run the exe. Once you install the cartogram tool after running this exe, it will be all set to go. Access ArcMap, and inside ArcMap, access ArcToolbox. Right click in the ArcToolbox window to create a toolset, add the cartogram tool, and run it. There are more details in the documentation in the tool itself, but it is pretty straightforward. Let me know if you have further questions. –Joseph

  3. gchribar says:

    What a great tool. However, I got an error message stating that the cartogram could not be created because the dataset contained negative values. I conducted a query for all values greater than -99, created a new shapefile and then the cartogram script worked. Is there a better, easier method?
    Thanls

  4. mirivilkhov says:

    Hi, does this version of the tool work with Arc 10.0? I have used the CartogramCreator in the past and that is not currently supported in the lastest version of the software.

    Thanks much-
    Kate Carlson

  5. Kaca says:

    Hi, does this version of the tool work with Arc 10.0? I have used the CartogramCreator in the past and that is not currently supported in the lastest version of the software.

    Thanks much-
    Kate Carlson

  6. cpoynter says:

    Hi Kate,

    I downloaded this tool and contaced Tom Gross about how to install for ArcGIS 10. These are Tom’s recommendations:

    ======================================

    It sorta works. There is a bug somewhere when you run it out-of-process, and it fails. To get it to work in-process you have to register both .dlls using esriRegasm.exe. I use the following command line:

    “C:Program Files (x86)Common FilesArcGISbinesriregasm.exe” /p Desktop /v 10.0

    You could also put the two .gif files and the Cartogram_Toolbox.xml file into your ArcGIS install under helpgp.

    C:Program Files (x86)ArcGISDesktop10.0helpgp

    ======================================

    I have to try this myself. Hopefully all will work well. Tom was going to try and fix things for a 10.1 version.

    Regards,

    Craig

    • foresterdave says:

      When I installed this in 10, the tool works but there is no help available. Since the documentation says read the tool help this makes it rather difficult to figure out how to use the tool.

  7. morrow.mark.a says:

    I have basic population data and the cartogram tool fails to create, says “from a related table”. What am I doing wrong?

    • jjkerski says:

      Make sure you have installed the correct version of the cartographic tool for your software (9.3 or 10). If you have already done that, then you might try posting your question on the larger ArcGIS forums. You will have more users seeing your post and can tap into the collective wisdom.

  8. rwfarley says:

    Incorrect results.
    I’ve been trying to create a Population Cartogram by US County. I’m using “Cartograms93″ and Arcmap 10.1. My results have been improving, but I still have a nearly 10 to 1 range in the Pop/Area of the result. E.g. Gilpin CO has a resulting Pop/Area of 62k, while San Francisco CA has a resulting pop of 685k.

    I’m using a modified US County shapefile, from which I’ve removed the portion of alaska that crosses the date line, so my data now range from about 64W to 180W and abt 17N to 73N. This seems to be better than when I used the full dataset ranging from 180E to 180W.

    How can I improve the results? Neighboring counties like San Francisco and San Mateo; or New York and Hudson are off by factors of 2 or 3

    There also seems to be a new algorithm that preserves peninsular features better. Note how Florida is less “bulbous” in http://www-personal.umich.edu/~mejn/election/2012/ than in the 2008 and 2004 figures.