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3.8 Roof Areas
Figure 12: Typical Roof Value Area Image
This study involved taking a sample of roof imagery from a test area and
comparing the luminescence values to those of the entire image to determine if a
distinguishing deviation in values existed for these features of the image. The
initial part of the experiment involved taking a sample number of roof values from
the orthophotography and converting them to a format suitable for individual
examination. The study involved a section of rural landscape in south county
Galway (Ordnance survey sheet no. 3012-c).
The aim of this part of the thesis is to try to obtain one of a series of benchmark
control values which can then be applied to the area polygons in determining
relative deviation of pixel values. In other words this section of the study is an
attempt to try to get a unique indicator for roof pixel values to form part of a key
for interpreting statistical values from the polygon being processed. It involved the
use of three image analysis software packages, but can be achieved using the
GDAL library alone (using GDAL_translate).
The first step involved editing the image (aerial orthophoto corresponding to the c
quadrant of OSI #3012-c) using OpenEV. This involved targeting the areas of
interest from the imagery based on building polygons captured by OSI vector data.
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