Geography Reference
In-Depth Information
TABLE 13.1. GI Analysis Types and Related GIS Operations
Type of GI Analysis Operation
Related GIS Operation
Spatial query and attribute query
Distance transformation
Connectivity, adjacency, visibility
Ranking, weighting
Multivariate analysis
Linear factor combinations
Monte Carlo simulations
Fuzzy sets
Note that GIS operations may not correspond to actual GIS commands.
basic “identify” operation are operations for determining the characteristics
of features based on their geographical relationship to other features, partic-
ular positions, or areas. Another type of query operation makes it possible
to select features based on their attribute values. This type of query is a sig-
nificant analytical tool for choosing features based on combinations of
attributes. It is often used after geographic information is combined to iden-
tify particular combinations of attributes.
One of the most used geographic information analysis types is widely known
by the associated GIS operation: overlay. Overlay in its simplest form
involves joining the vector or raster data from two data sets including the
attributes. The people who introduced overlay to GIS thought of this type of
geographic information analysis in terms of looking at interactions between
two or more transparent maps. The simplicity of this approach was very
attractive, as was its chief promoter's (Ian McHarg) emphasis on the overlay
operation as a method to incorporate environmental and social concerns
along with engineering perspectives in the planning of highways and other
large construction projects.
Many people refer to overlay as “integration,” but each GIS overlay
operation may or may not integrate. As McHarg, Dangermond, and many
others from the first generation of GIS developers point out, integrative
analysis based on overlay requires the interpretation of the overlay results.
Simply combining two (or more) data sets through overlay will only rarely
integrate geographically.
The combination geographic information analysis operation is prolific
due to its ability to take geographic information from different sources. As
long as the geographic information uses the same coordinate system, it is
possible to combine the GI, although most times additional query geo-
graphic information analysis operations are required before or after the
combination operation.
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