Envisioning Information Lecture 10 – Cartograms: A different way of drawing maps

Envisioning Information Lecture 10 – Cartograms: A different way of drawing maps Ken Brodlie kwb@comp.leeds.ac.uk ENV 2006

Maps have been traditionally drawn to represent area With topography indicated by shading Increasingly we use maps to represent properties about areas Here each state is shaded according to density of population Known as choropleth mapping Choropleth Maps http://www.cdc.noaa.gov/USclimate/states.fast.html ENV 2006

Strengths Weaknesses Discuss Strengths and Weaknesses ENV 2006

The cartogram is a response to these issues Rather than accurately reflect the area and superimpose shading to represent the variable.. .. Distort the area so as to reflect the variable directly Cartograms ENV 2006

Cartograms can be contiguous or non-contiguous Here is population of California by county as a contiguous cartogram Types of Cartogram ENV 2006

.. And now as a non-contiguous cartogram Types of Cartogram ENV 2006

Contiguous and Non-Contiguous Cartograms • Here is the US population example in both styles… ENV 2006

Perimeter-preservation ENV 2006

World Population Cartogram Acknowledgement: Examples taken from Web site of Dr Donald House http://www-viz.tamu.edu/faculty/house/cartograms ENV 2006

George Bush – Victory large or small? ENV 2006

Danny Dorling (recently Professor in Leeds) invented a special type of cartogram using circles of different size Types of Cartogram http://www.ncgia.ucsb.edu/projects/Cartogram_Central/index.html ENV 2006

Try the applet at: http://www.mapresso.com/dorling/dorlingexample.html Dorling Cartograms ENV 2006

British county populations evolving… ENV 2006

Acknowledgement: Last two slides from ‘Cartograms for Human Geography’, by D. Dorling, in Visualization in Geographical Information Systems, Wiley. Chernoff Face Cartogram! ENV 2006

Envisioning Information Lecture 10 – Cartograms: A different way of drawing maps