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is geometric. It is the set of all the geometries representing the spatial objects corresponding
to a particular combination of dimension members from one to many
spatial dimensions. It consists of a set of coordinates, which requires computing
geometric operations such as spatial union, spatial merge, or spatial intersection. A
second type of spatial measure is numeric. It results from the computation of metric
or topological spatial operators such as ???surface,??? ???distance,??? and ???number of
neighbors.??? Figure 4 presents the two types of spatial measures. A set of measures
(spatial and nonspatial) organized according to a set of dimensions (spatial and
nonspatial) form a spatial datacube.
In a SOLAP client interface, variants of the OLAP operators are used in order to
take advantage of the spatial multidimensional data structure and of the different
levels of detail of the spatial data. The general operators are drill-down, rollup (or
drill-up), drill-across, swap (or pivot), and slice and dice. These operations are
available in the different types of displays (maps, diagrams, or tables) and can be
specialized according to the type of dimension they manipulate (Rivest, B?©dard,
Proulx, & Nadeau, 2003). Thematic operations allow the manipulation of thematic
(or descriptive) dimensions, while keeping the same level of spatial and temporal
granularities.
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