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4.3 Marsh Test<br />
The testing for the marsh areas involved taking four known marsh areas (but<br />
geographically separate) from the imagery as ASCII co-ordinate files and using<br />
this data to extract the raster sections for spectral analysis. The sampling section<br />
of this study found marsh to have a relatively low level of standard deviation<br />
across the colour bands (when compared to the similar rough pasture type<br />
polygons). This might have been expected to change as there can be a relatively<br />
large degree of shade in these areas due to the presence of other vegetation –and to<br />
some extent this was the case. The samples, however, despite a high degree of<br />
standard deviation, did display some unique properties in line with the sampling<br />
section which allow them to be automatically classified. In general terms polygons<br />
with the value ranges displayed below will belong to either rough pasture or marsh<br />
(see sampling section, this is in reference to Irish small area polygons only).<br />
Rough pasture displays two peaks of values where the shade and vegetation<br />
contrast, the marsh samples did not have this distinction and the range of values<br />
graduated towards a peak (slightly lower than rough pasture ~10 on the converted<br />
greyscale).<br />
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