This page was retrieved from the Internet
Archive and has been archived locally for permanent and immediate
access by The Center for Spatially
Integrated Social Science at the University of California Santa
Barbara.
This page was retrieved from the Internet
Archive and has been archived locally for permanent and immediate
access by The Center for Spatially
Integrated Social Science at the University of California Santa
Barbara.
WHAT ARE CARTOGRAMS ?
A Cartogram is a map or diagram showing geographical statistical
information (Dorling 1995). In this context the term cartogram should
be taken to mean equal population cartogram. This distiction needs to
be made because ordinary maps are in fact a form of cartogram based on
equal land area. Cartograms differ from traditional maps as they use a
variable other than area to derive the size of areal units on the map.
WHY USE CARTOGRAMS ?
A major draw back of using traditional map based cartographic
representations for portraying human based socio-economic information
is that areas with high populations and high population densities, e.g.
cities are displayed very small on maps. Traditional maps therefore
tend to highlight patterns in the least important areas, i.e. where few
people live.
In contrast cartograms represent areas in relation to their population
size. As a result patterns are displayed in relation to the number of
people involved instead of the size of the area involved. Example 1
below, clearly shows how using a cartogram can give a vastly different
impression of overall trends.
Example 1
From the traditional map it is easy to get the impression that the
majority of areas have approxiamatly 56% (yellow and green) of the male
population of working age. The cartogram gives a different overall
trend, suggesting that the majority of areas have a male population of
working age of over 60% (red and purple on the map).
ADDING A TEMPORAL ELEMENT TO CARTOGRAMS
For a wider review of the benefits of cartograms and further
examples of cartograms I suggest looking at either Dorling D. (1994)
Cartograms for visualizing human geography in 'Hearnshaw H.M. & Unwin D.J.
'Visualization in GIS' or Dorling D (1995) 'A new social
atlas of Britain'.
We are particularly interested in developing animated cartograms to
show changing trends through the 19th and 20th centuries. Although much
work remains to be undertaken, example 2 shows how animated cartograms
can be used to display a twin pattern of overall rising numbers of
males of working age and the growth of population in London and
Lancashire / West Yorkshire.
Example 2
