May 2002
Beginner to intermediate
448 pages
13h 18m
English
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13.1 Introduction
From the user's viewpoint, the ideal GIS should include enough functions to perform all conceivable manipulations of geographical data. In practice, user needs comprise various tasks. So, as listed in Figure 13.1, an overview of user tasks defines the overall GIS requirement (Larsen 1991). The first two tasks in the table are customarily associated specifically with GIS and hence are often incorporated into infra-structures under the jurisdiction of national map agencies, military agencies, or public utilities. The remaining tasks are supported to a greater or lesser degree by the various GISs now on the market.
As a software system, a GIS usually comprises a set of software tools, including:
- Database and database management system (DBMS)
- User interface
- Query language (QL)
- Application functions and programs
Databases, DBMS, user interfaces, and QL have been discussed previously. The basic application functions employed in GISs are discussed in this chapter; the more specialized analysis functions are the subjects of Chapters 14 and 15.
The basic application functions often employ standard functions supported by the DBMS, the QL, and the user interface. The wide range of needs encountered requires numerous special GIS functions. Only a few GISs have all possible functions. In all cases, each function may be executed by one or more commands. The basic GIS functions may be divided into four main categories:
- Functions for data registering, entering and storing ...
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