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trends of bordering polygons mentioned above was detected and included in the<br />
flagged polygon set, where the histogram could be analyzed.<br />
Shade test sample 2<br />
(Pasture containing small areas of<br />
shade)<br />
76<br />
Mean pixel<br />
value<br />
Standard<br />
deviation<br />
Red 136.056 23.905<br />
Green 179.235 25.065<br />
Blue 114.285 14.684<br />
Table 17: Shade test sample value 2<br />
Although the mean pixel values matched those expected for pasture across the<br />
three colour bands the high level of standard deviation, suggests further<br />
examination could be necessary. A histogram representation shows the relatively<br />
higher pixel count across the values associated with shade but displays a clear<br />
peak for pasture. From the evidence of these samples it would seem safe to set the<br />
tolerance for standard deviation in both the red and green colour bands to a figure<br />
between 25 and 30; where any polygons exceeding this (even if they are bordering<br />
pasture polygons) would be flagged and exported to an examination set together<br />
with appended histograms.<br />
The final part of the testing took a sample from relatively clear pasture (little or no<br />
shade present) to see if the trend identified in the first two samples would continue.<br />
In other words if a large amount of shade resulted in a high pixel count and peak<br />
at the values for shade, and a smaller amount less so then the trend should show a<br />
simple peak for an area with little or no shade present. While this produced<br />
expected results, it was necessary to confirm the trend.
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