Different classification techniques will invariably result in different representations of the distribution pattern. Class boundaries change according to the mathematical procedures employed. Similarly, changes in the pattern of the distribution will result from the changes in the number of classes used.

A knowledge of the geographical phenomenon mapped is a vital factor in the determination of the number of classes to be used, as is the decision to use greyscale, monochrome or spectral adjacency in the map output.

Where a greyscale or monochromatic output is to be used, then as previously shown, no more than 6 classes is advisable to be used in the classification. Perception of tonal value difference becomes more difficult as the number of classes increases; eg

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