Transforming the mosaic - The Visualization of Spatial Social Structure - page 131

discontinuities), to differentiate sampling error from change, to the technical
difficulties of processing it (what type of change is to be seen), to, finally, the
imaginative hurdles that have to be crossed in portraying it (creating still images
of change).

5.2 Forming the structure

The decennial census ... was a solution to the problems of data col-
lection and dissemination of the mid-19th century. Yet we have only
the vaguest notions of how to exploit the new technology in this area;
our perceptual systems are so geared to conventional display .

(Goodchild, 1988, p. 318)

...

In past research, geographers often stumbled at the first hurdle when gathering
information about change; this hurdle was coping with temporal discontinuities.
Temporal discontinuities occur when units of population have their spatial bound-
aries altered. Temporal discontinuity is continuously reoccurring, and is itself one
aspect of change. As people move, so do the collating boundaries move around
them, eternally attempting to encompass them adequately. We need to encompass
these changes within our pictures.
Practically every person in Britain is counted in the census every ten years. 2
The simplest single number to be gathered from this is the total change in pop-
ulation, an increase of however many thousands between 1971 and 1981. How
is this simple loss or gain of people distributed over our landscape? During
this period Britain undertook its greatest ever redistribution of administrative
boundaries - everything altered. Very few figures collected before the mid-1970s
could be directly compared with those that came after. The changes in 1965 and
1974 were as great as all those from 1975 to 2011.
Geographers often addressed the problem of change with the crude solution
of aggregation. 3 The method is to find a set of large areas either side of the time
period whose summed figures can be directly compared. This solution causes a

2 Many minor nuances must be included when calculating the change between censuses: 'Perhaps
most fundamentally, the 1981 Census was taken on the night of 5 April (before Easter and out of
term for higher education institutions) and the 1971 Census was taken on 25 April (after Easter
and in term for higher educational institutions). In towns where the number of holiday-makers and
students cause seasonal fluctuations in the size of the population, this three-week difference is likely
to have some impact on the results obtained' (Norris and Mounsey, 1983, p. 276).
3 A policy of aggregating areas can prevent a proper study of geographical change: 'The largest
tract in the region, in terms of 1971 and 1981 EDs, occurred in the district of Bracknell in Berkshire,
with 98 1981 EDs and 60 1971 EDs combining to form this comparable “small” area (as defined
by OPCS). This tract is therefore a good example of an area in which great change is taking place,
but which - as a consequence - permits the least local study in the region of this change, due to the
large size of the tract' (McKee, 1989, p. 4).