Classified data often manifest a salt-and-pepper appearance due to the inherent spectral
variability encountered by a classification when applied on a pixel-by pixel basis (Lillesand
and Kiefer, 1994). It is often desirable to “smooth” the classified output to show only the
dominant (presumably correct) classification. Ground truth or field survey is done in order to
observe and collect information about the actual condition on the ground at a test site and
determine the relationship between remotely sensed data and the object to be observed. It is
recommended to have a ground truth at the same time of data acquisition, or at least within the
time that the environmental condition does not change. Overall classification accuracy is
calculated after collecting a good number of ground control point after supervised
classification.