Spatial relations between thematic properties
Other situations depend on the relation between elements and the phenomena under consideration. The relation is not
constant; it's a function of distance. This corresponds to phenomena which move in space having an origin and a destination
and disperse progressively in the geographic space such as noise or a cloud of smoke. In addition to the modeling of
phenomena,
GIS are applied to define the limits of proximity or neighborhood as well as to classify neighborhood. When does an object
belong to another object's neighborhood? The answer to this question depends on the interpreter. The concept of neighborhood
depends on the object of interest.
A spatial relation identifies all the properties between the spatial units. The spatial relation is always related
to the concept of neighborhood or of liaison, which makes two phenomena depending on each other. Hence they are expressed
by the geometry in the case of neighborhood or by liason functionally expressed in an attribute.
The concept of neighborhood is discussed in the unit "Topological Relations". The concept of topology is discussed in
the next unit.