B. Unsupervised
Rather than defining training sets and carving out pieces of n-dimensional space, we define no classes beforehand and instead use statistical approaches to divide the n-dimensional space into clusters with the best separation using clustering algorithms. After that, we assign class names to those clusters. It is distinguished from supervised learning by the fact that there is no a priori output. The analyst requests the computer to examine the image and extract a number of spectrally distinct clusters. The result of unsupervised classification is not yet informative until the analyst determines the ground cover for each of the clusters. Common Unsupervised classification Methods are -
a. Simple One-Pass Clustering
b. K Means
c. Fuzzy
d. Minimum Distribution Angle
e. Adaptive Resonance