The wood and the trees - The Visualization of Spatial Social Structure - page 225

depicting the changing spatial distribution of unemployment could be to draw a
series of rings inside the circle representing each place. There would be one ring
for each of twelve years, like the old bark of a tree trunk, and the rings would be
coloured increasingly darker to show the more people there were out of work.
It did not work (Figure 8.1). That image, if created, holds little meaning, even
when only a few dozen circles are employed. This is because it is not possible
to compare across space any more, as space is cut up by circles of time. Each
circle is an accurate individual record of unemployment in that place, but the
places could now not be seen as a group. 4
Interestingly, when hexagons are used rather than circles the eye is not so
drawn to the centre of each converging set of rings. It is possible to more easily
switch between looking at the centres, looking at the outer rings and looking
at the middle years. Patterns become more easily picked out, but it is still pos-
sible to become overwhelmed by the variety between smaller and larger areas
as more urban and more rural parts of Britain diverged in the experiences of
unemployment of their respective populations.
One of the most popular forms of glyph in current use is the polygon (often
called the 'radar chart'), or its inverse structure, the weather-vane graph. This
is formed by representing each case as a point and projecting spokes for each
variable associated with that point, out from it at regular intervals, their lengths
drawn in proportion to the value of each variable being shown. If the tops of the
spokes are connected an irregular polygon is drawn, containing aspects of size,
shape and orientation.
This symbol works well when the direction in which the spokes point has
some meaning, for instance when showing wind speed in certain directions or the
numbers going that way to work. The polygon can produce ambiguous images,
however, as two different sets of numbers create the same object. Also, as the
number of variables increases, the polygon glyph quickly becomes a formless
blob. The basic problem with all of these methods is that they are not producing
naturally comprehensible images. What is needed are collections of objects we
are used to seeing as a group and for which we already have the visual skills
needed to assess as a group.

4 Government in Britain by the early 1980s somewhat reduced the difficulties of visualizing
employment trends by reducing the supply of information on employment: 'Between 1971 and
1978 the Census of Employment was held annually and thus became known as the Annual Cen-
sus of Employment (ACE). In the early 1970s, processing of the data was carried out clerically
(which proved costly) but, by the 1977 and 1978 Censuses, computerised processing was under-
way. However, this was insufficiently planned and led to the delay of the 1977 and 1978 Census
results. As a result of these delays and in an attempt to find economies following the Rayner
Report, the 1979 and 1980 Employment Censuses were cancelled . Since 1978, the Census of

Employment has been carried out only once every three years, in 1981, 1984 and 1987' (McKee,
1989, p. 9).

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