Classification

Classification is the process in which, objects are placed in groups (or classes) having identical or similar features. The information is conveyed through identification of the group boundaries. Classification brings relative order and simplicity, and helps to organize materials for communication.

Some of the most common operations of classification are (Robinson et al. 1995, p. 460f):

Grouping: The grouping of similar data elements into categories referred to as range grading.
Typification: The selection of position and the modification of the data element at that position based on other data elements around the selected position to create a "typical" data element to portray on the map at that position.
Other forms of typification may include the exaggeration or actual creation of map data in an attempt to typify.

Visualise a Classification Example

The following example is a typical classification operation.
Roll over the picture to get a zoom.

(Schweizerische Gesellschaft für Kartographie 2002)

In thematic mapping, classification can be carried out with quantitative or qualitative information.

Qualitative classification
Qualitative data might include the identification of geographical regions: corn belt, sun belt, etc.

Map example of qualitative classification (Spiess 1993)

Quantitative classification
Quantitative classification generally divides entire data into numerical classes, and each value is placed in its proper class. Only class boundaries are shown on the map.
Map example of quantitative classification (Spiess 1993)