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Figure 56: Blue colour band for marsh test 3<br />
The fourth sample known marsh polygon used in the test was from an area to the<br />
south of the sample image (below). As with all others it formed an irregular<br />
polygon bordered by other non-marsh areas. There were also some trees and other<br />
vegetation present in the area, which was something present in all the marsh<br />
samples. This suggests that the type of ground cover being described is often<br />
something that occurs in transitional areas, and the difficulties associated with<br />
getting clear spectral values (in terms of low levels of standard deviation) are a<br />
result of this variation. The samples, however, were consistent with the other two<br />
large marsh test polygons, and the pixel count for the red and green colour bands<br />
peaked within the expected range.<br />
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