Fundamental operations
- 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.