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Road test sample 1 Mean pixel value Standard deviation
Red 205.889 8.18
Green 228.167 11.289
Blue 178.778 12.73
Adjacent spectral values sample 1
(pasture)
Mean pixel value Standard deviation
Red 91.539 6.573
Green 138.706 7.504
Blue 92.519 10.84
Table 2: Road test sample value 1
The first test sample took an area of road and a sample area from an area of
pasture adjacent to the road. This can be assumed to be a recurring set of values
that can be located in most aerial imagery that this study is considering. In the test
the values for standard deviation from the mean across all three colour bands in
both samples did not vary to any large extent and can be omitted as reference
values for the search algorithm looking to match a set of values as pasture using
the nearest road polygon as key. In contrast there was a large difference in the
mean values for all three colour bands with the road polygon containing pixels of
a mean 50% higher for the red, 40% higher for the green and 50% higher for the
blue colour band. This discernable difference allows a range surrounding this
relative difference to be included into the search and areas of pasture to be
identified. Note: potential candidates for a pasture set of polygons are also cross
checked against other relative values, outlined in later sections of this sampling
study part of the thesis. A result of this variance means that once the known areas
are identified the road set can be compared against unknown polygons adjacent to
it and, given similar levels of standard deviation and proportional mean by colour
band outlined above, the unknown polygons can be placed in a pasture polygon
set for further reference and confirmation as the analysis progresses.
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