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Lesson Navigation IconGeneralisation of Map Data

Unit Navigation IconGeneralisation Concepts

Unit Navigation IconGeneralisation Procedures

Unit Navigation IconGeneralisation Methods

LO Navigation IconCommon Rules for Generalisation

LO Navigation IconGeneralisation Workflow

LO Navigation IconGeneralisation Algorithms

LO Navigation IconGeneralise your Map

LO Navigation IconSummary

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Unit Navigation IconRecommended Reading

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Generalisation Algorithms

Over the past 25 years, automating map generalisation has seen major improvements. Generalisation algorithms constitute the building blocks of the automation process. Generalisation algorithms are more common with individual types of objects such as lines or polygons. Generalisation of the map as a whole is normally conducted manually.

Several algorithms are used for generalisation. The most typical are classified as following:

  • Algorithms for simplification: They include the independent point algorithms, e.g. the random selection of points, as well as the local processing algorithms, and global routines. The Douglas-Peucker (Douglas-Peucker, 1973) is the most representative of this class.
  • Enhancement algorithms: They include the exaggeration process and the smoothing process.
  • Collapsing algorithms: This operation is mainly used for broad rivers because they are usually digitized by their bank lines, but needs to be reduced to a centre line.

To find more information about algorithms used in generalisation, you can have a look on the following project from the University of Zurich: Agent_Esprit.pdf (493 Ko)

The Douglas-Peucker Simplification Algorithm

Discover graphically the Douglas-Peucker generalisation algorithm with the following animation. This simple and easy to understand algorithm is used for road simplification: the cartographer has just to define the tolerance value (according to the degree of generalisation), and the road is then generalised segment by segment.

Source:C.Plazannet readapted by IKA - ETHZ
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