Map Generalisation

When depicting information on a map the cartographer has to make choices on how to display the sometimes complex and very dense information without losing the flavour and meaning of what they is attempting to portray. There are several generalisation techniques that the cartographer can employ to help in this sometimes very difficult process. Some of these techniques such as displacement, simplification, combination and selection are discussed below.

Displacement is where due to the density of information symbols need to be shifted spatially so that they don’t overlap and therefore obliterate each other on the map.

Satellite image courtesy Google Maps

For example here you can see when you compare the satellite image on the left with the map on the right, you can see that some of the building symbols have been displaced so that they would not appear to be on the road.

Simplification is employed particularly for linear symbols where it is not feasible to show every bend and wiggle, this is illustrated in the coastline example below where the image on the left shows too much detail but when simplified looks much cleaner.


Another important factor when employing generalisation techniques is to maintain the character of the feature being generalised. The sample below illustrates where the original craggy nature of the coastline has been lost by smoothing the linework in the simplification process.

Smoothing however can be a useful generalisation technique in the right context, such as for river and streams where a smooth flowing line is more in character with the feature being represented.

Selection is a technique utilised when there are way too many features of the same type to all be displayed, the cartographer makes a selection of which features to display and which to leave out.

The final technique to be discussed here is combination, where a number of features are combined together to be displayed as one feature, for example a small village made up of numerous buildings, but instead of showing the individual building symbols the cartographer combines them into one village symbol.

Related Links

Map Scale

Map Symbology

Torography

The Cartographic Conundrum

Mapping Themes

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