Geography Reference
In-Depth Information
and which is based on known factors of map use' (Crampton, 2001: 237). Com-
munication is complete only when the coded message has been deciphered and
interpreted. The first models to explain cartographic communication followed the
general and rather mechanical scheme of transmission of information: the sender
codifies information using sign vehicles, and these signs are submitted to the
receiver, who has to decode the information. For a communication process to be
complete, this requires a common repertoire of signs between 'sender' and
'receiver' of the information (Hake, 1973). The codification of signs within the com-
munication process is crucial for their correct interpretation: all signification (the
relation between sign vehicle and interpretant) is defined by an explicit or implicit
'code' or convention between the individuals for whom the sign serves a communi-
cation function. The measure of communication efficiency in the mapping process
is related to the amount and accuracy of information transmitted. In this under-
standing, the cartographer's task is seen as achieving better approximations
between raw data and the map image in order to reduce distortion. The earliest
models of cartographic communication treated each stage in the process as a
black box, yet later models were concerned with a sub-process analysis of the
communication system (cf. Kolá ˇn´, 1970). The more comprehensive models for
example considered 'seeing' as an active process - a transaction between the indi-
vidual and his environment, in which the viewer creates some kind of order from the
essentially disordered array that is the visual stimulus. Of interest for cartographic
research is then not just the map, its message and the uses to which it is put, but
also the knowledge that the user brings to the map-using environment, such as
personal experiences or spatial concepts of the world. Cartographers began to
realise that it was vital to be specific about how maps were used, what map-using
tasks were being performed, how mapped information was extracted and how its
design influences that use (Hopkin and Taylor, 1979). This sparked interest in the
processes of map reading, but also in the way in which the different elements in
the map 'were put together' to communicate most efficiently the message that the
map author wished to send.
Highly influential for cartographic science has been Bertin's (1983) interpre-
tation of the cartographic communication process in terms of semiology.
2
Bertin
argued that one should match the symbol to the referent, by for instance using dis-
crete symbols (such as choropleth maps) to represent discrete data (such as sales
tax rates), and continuous symbols (for example isarithmic maps) to show continu-
ous data (for instance temperatures). These relationships are expressed in the
'visual variables', a set of map graphic building blocks which match spatial phe-
nomena. Bertin's systematic framework for the use of visual variables in thematic
maps (dimensions of the map, size, brightness, colour, form, texture, orientation) is
widely accepted by most cartographers nowadays (see Plate 1).
