View/Open - ARAN

with the authors work for a software development company (Enterra) which is
involved in developing GIS software and the algorithm was also an attempt to find
a solution to identifying building signatures within the software. The paper
develops a work around for identifying polygons which are consistent with
buildings on a map. He describes this as an ordered point set. This could provide
useful background information should spatial deviation pattern recognition ever
become an option. It is not within the scope of the thesis to modify the algorithm
but nevertheless Duradev’s study provides a possible alternative to the spectral
deviation method of identifying additional data.
The author notes that building signatures in many cases will not look “neat and
beautiful” (Duradev, P.109). By this he is referring to the fact that the polygon
will not conform to a standard shape which would be easily identified. It should be
noted that the author acknowledges that a similar algorithm exists for the product
of another software provider, ESRI (with Arc View software) and that the test of
the algorithm was carried out on uncoordinated data; implying that any application
of the algorithm in this thesis would involve a high level of modification for
something that could be obtained from a desktop application. It is however, useful
to consider the methodology for breaking down the problem (the author outlined
an implementation algorithm before considering the process steps required).
Duradev broke down the necessary implementation into five steps, starting with a
search for a convex polygon inscribed within the shape being identified. He then
suggested that if the polygon shape returned from this was bigger than the
maximum (original shape) then the new polygon should be considered as the
maximum, otherwise another convex polygon within the shape should be
identified. This step is repeated until all the polygons have been searched at which
point the centre of the polygon is searched and the result returned.
Duradev then stated the mathematical steps that would be required to implement
the steps he outlined; namely –take a start point (on the polygon) for the search,
take the neighbor vertex in a set rotation –if this point matches the starting point,
return the resulting polygon; if the point addition results in a positive vertex then it
is added to the polygon, otherwise the neighbor vertex is selected again. This
160