2. • Theoretical Models of GIS used for obtaining
information from real world objects/data are
classified into 2 types.
– 1. functional elements of GIS
– 2. fundamental operations of GIS
• Conceptual models however represent only
operation or composition of GIS system, and
do not talk anything about the nature of data.
3. • The components in the above mentioned
models are almost similar to the different
software components in ‘general purpose GIS’
systems.
• To overcome these limitations, Bracken and
Webster (1989) suggested an alternative
classification of theoretical models, and it
comprises of 3 components.
4. – Problem-processor model
– Database model
– Interface model
• However, this is still considered as software
oriented approach, and is not dealt in our
present discussion.
5. Functional Elements of GIS
• Bracken. and Webster (1987) outlined four
functional elements to address the GIS
technology.
– database approach
– process-oriented approach
– application oriented approach
– toolbox approach
6. • Database approach stresses the ability of the
underlying data structures to contain complex
geographical data.
• The process-oriented approach focuses on the
sequence of system elements used by an
analyst running an application
7. • An application oriented approach defines GIS
based on the kinds of information manipulated
by the system and the utility of the derived
information produced by the system.
• toolbox approach emphasis as the software
components and algorithms that should be
contained in a GIS
8. Fundamental Operations of GIS
• This approach considers the functions which
GIS is able to perform.
• The operations discussed in this section fall
entirely within the manipulation-and-analysis
subsystem which is discussed before.
• Hence, all these operations are completely
internal to GIS.
9. • The fundamental classes of operations
performed by a GIS have been characterized as
'map algebra operations, in which the
processing operations are considered as similar
to the mathematical operations.
10. • The 'classes of analytical operation' are divided
into
– Reclassification
– Overlay
– distance/connectivity measurement and
– neighborhood characterization of the data.
11. • Reclassification operations transform the
attribute information associated with a single
map coverage.
• Overlay operations involve the combination of
two or more maps according to Boolean
conditions and may result in the delineation of
new boundaries.
12. • Distance and connectivity measurement
include both simple measure of interpoint
distance and more complex operations such as
the construction of zones of increasing
transport cost away from specified locations
13. • Neighborhood characterization involves the
values to a location both summary and mean
measures of a variable, and include smoothing
and enhancement filters.
