Chapter 8
Spatial data modelling, collection and management Rolf de By Otto Huisman Richard Knippers Menno-Jan Kraak Alfred Stein 8.1
Geographic Information and spatial data types
8.1.1
Geographic phenomena
Defining geographic phenomena A GIS operates under the assumption that the spatial phenomena involved occur in a two- or three-dimensional Euclidean space. Euclidean space can be informally defined as a model of space in which locations are represented by coordinates—(x, y) in 2D and (x, y, z) in 3D space—and distance and direction can defined with geometric formulas. In 2D, this is known as the Euclidean plane. To represent relevant aspects of realworld phenomena inside a GIS, we first need to define what it is we are referring to. We might define a geographic phenomenon as a manifestation of an entity or process of interest that:
Euclidean space
geographic phenomena
• can be named or described; • can be georeferenced; and • can be assigned a time (interval) at which it is/was present.
Relevance of phenomena for the use of a GIS depends entirely on the objectives of the study at hand. For instance, in water management, relevant objects can be river
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