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- 973 — 
Survey Results 
In order to make useful and easily understandable comparisons 
(as a source of 'open space! data) between the value of black 
and white and colour infra red aerial photographs the 
information was compiled in various ways. 
The first comparison was a statistical output showing the 
total amounts of open space recorded in the major categories 
only. (Figure 5). This did not include details of the 
vegetation, surface cover or condition. 
The results clearly show that, at this level of information, 
there is virtually no difference in the type or amount of 
open space information which can be derived from the two sources. 
However when details of the vegetation cover and its condition 
are included, then some significant differences do emerge. 
Figure 6 shows that the colour infra red photography is a 
much more sensitive indicator in identifying the extent to 
which the vegetation is being managed. A suite of computer 
programmes was developed for calcomp mapping based on all 
the information fed into the system. 
Figure 7 shows a computer map of open space derived from the 
black and white photography, whilst Figure 8 shows the same 
area mapped from colour infra red photography. These map 
symbols relate to the notation of Figure 2. 
Figure 9 shows those grid cells which the computer identified 
as different, between the maps compiled in Figures 7 and 8, 
though some of these differences were not true differences 
in the air photo interpretation but resulted from a variety 
of other reasons. 
These included some misorientation of the grid on the two sets 
of photography because of slight differences in scale and 
photo tilt, and of land use changes which had occurred between 
the two sets of photography. These 'apparent! errors (Figure 
9) were identified and recorded, and another map was compiled 
(Figure 10) showing the !real! differences, in the data 
collected, between the two sets of photography. 
The two sets of photography were stereoscopically examined 
again, only this time one photograph from each set was viewed 
simultaneously i.e. a black and white photograph on the left 
with a colour infra red on the right - each covering the 
same area. 
Those areas where a difference occurred, between left and right 
photographs, were noted, and the reasons for the difference was 
recorded. 
The differences in the information obtained were classified 
into two major groups and eight sub-groups: (Figure 11)