May 2002
Beginner to intermediate
448 pages
13h 18m
English
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16.1 Theoretical Foundation
It is prerequisite in the visualization phase that a preliminary treatment of the information has been carried out in the form of conceptual modeling, and that the data selected are available in digital form, normally in a database. Conceptual modeling is mentioned earlier in this book. This discussion is therefore limited to the process used to visualize the data.
16.1.1 From data to display
When visualizing geographical data, it is important to be aware that one often operates with a series of fundamentally different types of data, each of which must be handled in a different way. We have already mentioned that geographical data are represented in the data model by points, lines, and areas (or raster). The same three geometric forms are essential to the presentation of geographical data in maps. In addition, geometric volumes such as terrain surface, buildings, and other three-dimensional objects can be represented.
Attribute data are divided into two categories: qualitative and quantitative data. Qualitative data describe the type of objects, such as different types of vegetation or different types of language. At the quantitative level (nominal level) the objects can only be classified into groups. As an aid to visualization, it can be useful to subdivide qualitative data into those that are conceived of as different but associative, and data that are conceived of as clearly different (selective) (Bertin 1983). Quantitative data specify number; they ...
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