Keyes, L. and Winstanley, Adam C.
Fourier Descriptors as A General Classification Tool for Topographic Shapes.
Proceedings Irish Machine Vision and Image Processing Conference.
Automatic structuring (feature coding and object recognition) of
topographic data, such as that derived from air survey or raster scanning largeÂ
scale paper maps, requires the classification of objects such as buildings, roads,
rivers, fields and railways based on their shape. There is a considerable body of
published work on the identification and classification of objects within images.
Recognition is based on the matching of descriptions of shape. Several
techniques have proved useful such as boundary chain encoding and moment
invariants. The technique used here uses Fourier Descriptors. Based on a
Fourier analysis technique applied to the boundary coÂordinates of an object
expressed as complex numbers, Fourier descriptors are widely used in image
processing to describe and classify shapes. The shape descriptors generated
from the Fourier coefficients numerically describe shapes and can be
normalised to make them independent of translation, scale and rotation.
Classification is performed by comparing descriptors of the unknown object
with those of a set of standard shapes, finding the closest match. Most
applications using Fourier Descriptors deal with the classification of definite
shapes, for example identifying a particular type of aircraft. To identify
topographic objects the technique needs to be extended to deal with general
classes of shape. Fourier descriptors are evaluated as general classifiers applied
to broad classes of topographic shape (buildings, fields, roads etc.). To analyse
their effectiveness, a corpus of shapes of classified objects was extracted from
topographic largeÂscale digital maps. The descriptors of each shape were
calculated and the results analysed. These indicate that normalised Fourier
descriptors alone are unsuitable for such general classification. However, when
applying the same Fourier method combined with other techniques it was found
that they could help to discriminate between some classes of objects.
||shape analysis, shape description, object recognition, Fourier descriptors
||Faculty of Science and Engineering > Computer Science
Dr. Adam Winstanley
||17 Dec 2002
|Journal or Publication Title:
||Proceedings Irish Machine Vision and Image Processing Conference
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