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lue. Another indicator present in all the samples was the fact that there was an
increase in disparity between the red and green colour bands -18.2% for the image
as a whole, compared to almost 30% across the samples. It is the red band which
is the most valuable indicator of this type of ground cover, with over 25% lower
value from the image mean. While coniferous will have been captured and
indicated as a level in the OSI vector data, smaller areas of this type of ground
cover will be typically present along the margins of small area polygons close to
urban areas. In particular a polygon closed by what is called a peck in the vector
data layers could be analyzed for the mean red colour pixel value converted to
greyscale and compared to the image whole. If the variation is close to 25% lower,
then it is probable that either this type of tree cover is present. It should be noted
that further spectral analysis (involving swapping of the colour bands) can present
additional indicators, which will be applied later in the study.
There are several implications of being able to identify coniferous vegetation in an
urban area; it indicates permeable surface area for planning/ flood modelling. In
the context of this thesis it allows a section within the study area to be identified
and adjoining areas to be measured against; for example, once the presence of
coniferous vegetation is detected image processing could be applied to eliminate
this from the result set from the target polygon –allowing another analysis to be
run on the remaining surface area.
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