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4.1 Pasture Test
Four areas of pasture were sampled across varying degrees of shade and
unbounded (from vector data) internal ground cover outside pasture (exposed
rock). The first of these was an area in the south west of the sample area and
comprised a polygon surrounded by five fence vectors close to the road. The
sample was chosen to see if the expected values for the man and standard
deviation across the colour bands would be reflected in a section of image with a
relatively high degree of variety in terms of ground cover.
The data was sampled using the Radius software where the polyline values were
exported to an ASCII file. This process will be easier once GML format spatial
data becomes available (not available at the time of writing but will be over the
next few years, OSI 2010). This process has two requirements in order for the
polygon to be correctly sampled:
• Firstly the line orientation needs to be the same for all polylines which
bound the sample polygon, by convention this is anticlockwise (left of the
line direction falling on the inside of the area to be extracted).
• Secondly the first and last co-ordinates must match, with no other
duplicate values present in the file.
These qualifiers can be validated at the time of extraction once GML data is
available, however for this study a text editor was used to search duplicate values.
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