Environmental Engineering Reference
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On the one hand this is due to the presence of irrelevant
local minima and local maxima in the image. On the other
hand, the reason is the presence of texture effects derived by the
spatial interaction between the size of the object in the scene and
the spatial resolution of the sensor (Pesaresi and Benediktsson,
2001). This is the reason why the input image is chosen to be the
adaptive filtered one.
The final step of the procedure is then a recombination of the
classification and the segmentation maps. This is accomplished
byaassigningtoeachsegmentauniquelabelaccordingto
the label of the majority of the pixels in it (''majority voting
algorithm''). However, to preserve situations where the majority
is extremely challenging, a stability threshold is introduced. If the
votes of the most abundant class in a segment do not overcome
the ones of the second most voted by more than this threshold,
the segment is considered a mixed one, and no assignment to
a unique class is performed. In order to show very quickly the
different phases of the procedure, Figure 3.4 provides the outputs
(a)
(b)
(c)
(d)
FIGURE 3.4 Sample outputs of the various steps of the processing chain when applied to part of an image over Ica, Peru:
(a) original image ( c
Geoeye, 2007); (b) the initial classification; (c) the output after the watershed segmentation algorithm;
(d) the final classification map.
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