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planet will always have fluid boundaries. In this example the change from marsh<br />
to rough pasture is a gradual one, and does not correspond to a single vector.<br />
Various solutions such as an additional transitional polygon instead of a linear<br />
boundary are simply methods of belting the square peg of a gradual change into a<br />
relational database. Although the study is attempting to identify statistical data<br />
(percentages of types of land cover) that can be appended to the entry for a given<br />
area polygon in a spatial database in this case a bitmap displaying concentrations<br />
of values corresponding to marsh might be more appropriate.<br />
When the values obtained from marsh were compared to three sample sections<br />
from other polygons in the study some unique proportional variations emerged.<br />
The purpose of the study is to iteratively reduce the quantity of unknown (in terms<br />
of land usage) polygons in the search area by appending values derived from the<br />
aerial photograph. The sample areas used in this test were not from any of the<br />
original samples used to obtain baseline spectral data for the land type they<br />
represent but were chosen to see if a reliable (or at least significant) proportional<br />
deviation could be observed. The three sections sampled were pasture (which had<br />
been recently cut), mixed forestry (chosen because of the variety of spectral values<br />
that this type of cover represents) and paving (taken from a yard surrounding<br />
buildings but similar to any of the road and track hard surface areas sampled<br />
elsewhere in this study).<br />
All three sample areas shower unique properties consistent with the sampling used<br />
for their respective baseline values but also useful in terms of obtaining a key for<br />
identifying polygons of marsh. As was mentioned above these will generally fall<br />
within a polygon composed of vector polylines but it can occasionally be the case<br />
where the marsh was not fully enclosed. It may be necessary to introduce a<br />
process that retains all the polygons containing marsh symbols but displaying<br />
spectral values outside those expected for that type of land cover for verification –<br />
this, however, was not the case for the samples used in the study.<br />
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