Standard methods of feature classification

Desktop GIS software such as ArcGIS, MapInfo and QGIS offer a number of classification methods. The most commonly featured are Natural Breaks (Jenks), Equal Interval, Quantile, Standard Deviation and Manual.

Natural Breaks was developed by George Jenks. This method uses clusters and gaps in the data to create classes.

Equal Interval, as it name indicates, creates classes which are of equal value ranges. For example if the value is between 1 and 100 and the number of classes is five, this method creates classes from 1-20, 21-40, 41-60, 61-80 and 81-100.

Quantile will create an equal number of features for each class in this method. For instance if you have a 100 features and four classes then each class will contain 25 features.

Standard deviation will create classes based on a specific number of standard deviations from a mean value.

Finally if you decide to use a manual method you set you own class breaks according to your requirements.

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