Envisioning Information
Lecture 10 – Cartograms: A
different way of drawing maps
Ken Brodlie
kwb@comp.leeds.ac.uk
ENV 2006
10.1
Choropleth Maps
•
Maps have been traditionally
drawn to represent area
– With topography indicated by
shading
http://www.cdc.noaa.gov/USclimate/states.fast.html
•
Increasingly we use maps to
represent properties about
areas
– Here each state is shaded
according to density of
population
– Known as choropleth mapping
ENV 2006
10.2
Discuss Strengths and Weaknesses
•
Strengths
•
ENV 2006
Weaknesses
10.3
Cartograms
•
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
ENV 2006
10.4
Types of Cartogram
•
Cartograms can be contiguous
or non-contiguous
– Here is population of California
by county as a contiguous
cartogram
ENV 2006
10.5
Types of Cartogram
•
.. And now as a non-contiguous
cartogram
ENV 2006
10.6
Contiguous and Non-Contiguous Cartograms
• Here is the US population example in both styles…
ENV 2006
10.7
Perimeter-preservation
ENV 2006
10.8
World Population Cartogram
Acknowledgement: Examples taken from Web site of Dr Donald House
http://www-viz.tamu.edu/faculty/house/cartograms
ENV 2006
10.9
George Bush – Victory large or small?
ENV 2006
10.10
Types of Cartogram
•
Danny Dorling (recently
Professor in Leeds)
invented a special type
of cartogram using
circles of different size
http://www.ncgia.ucsb.edu/projects/Cartogram_Central/index.html
ENV 2006
10.11
Dorling Cartograms
• Try the applet at:
http://www.mapresso.com/dorling/dorlingexample.html
ENV 2006
10.12
British county populations evolving…
ENV 2006
10.13
Chernoff Face Cartogram!
•
Acknowledgement:
– Last two slides from
‘Cartograms for Human
Geography’, by D. Dorling, in
Visualization in Geographical
Information Systems, Wiley.
ENV 2006
10.14