Cartographic map design
Lorenz Hurni
Institute of Cartography ¦ Institut für Kartographie
ETH Hoenggerberg ¦ ETH Hönggerberg
CH-8093 Zurich ¦ CH-8093 Zürich
Switzerland ¦ Schweiz
According to the definition of the International Cartographic Association ICA
(www.icaci.org), "a map is a symbolised
image of geographical reality, representing selected features or characteristics,
resulting from the creative effort of its author's execution of choices, and is
designed for use when spatial relationships are of primary relevance. Cartography
is the discipline dealing with the conception, production, dissemination and study
of maps." The German philosopher Jürgen Mittelstrass also describes
one of the major tasks of cartography, although his text is not specifically directed
to cartographers: "The differences between information, opinion and knowledge
are becoming less and less clear, especially with mass media.
Though modern information technologies like Internet offer an almost complete
encyclopaedia, this wealth of unprocessed information can by no means be considered
knowledge. The selection and processing based on thematic competence which characterise
knowledge and which enable understanding are missing." In order to fulfill
this goal two principles are of paramount importance in cartography: Generalisation
and symbolisation.
There are several process included in generalisation. The first step, however,
is always the selection of the information to be communicated by the map. Then,
it is time to group the generalisation manipulations to be performed on the
selected data into two main types:
- Semantic generalisation: Based on the initial choice of the relevant information
to be presented on the map, semantic generalisation is closely related to
classification, and aggregation, as well as symbolisation or exaggeration.
Semantic generalisation has a main objective of simplifying the presented
data, so at a given (small) scale the complexity of the map does not make
the map impossible to read. Semantic generalisation normally takes place before
geometric generalisation.
- Geometric generalisation: The complexity of the graphic characteristics
of map objects may still be too great to show them clearly, especially if
the scale of the map becomes smaller. So, the objective of geometric generalisation
is to preserve the important parts of the data and eliminate or simplify the
less important ones in order to create map that will have good visual communication
characteristics.
ICA defines the following generalisation operators: Selection, Simplification,
Omission, Smoothing, Displacement, Aggregation, Classification, Symbolisation,
Exaggeration.
Symbolisation means to assign to a geometric object a specific graphic appearance,
like for instance line width, line style or colour.
Both generalisation and symbolisation processes are closely connected since
changing an objects appearance will have an influence on the element geometry
and vice versa. In order to draw a graphically proper map, the sum of numerous
individual graphic adjustments make up the overall readability.
In general, and especially with detailed topographical maps such as orienteering
maps - map makers tend to put too much information in their products, filling
up the limited space. To follow the rule "less is more" can be recommended
in almost all map projects.
The presentation in PDF file (2.4 MB)