Introduction To GIS (Geographic Information Systems)

A Geographic Information System (GIS) links spatial information (CAD) to alphanumeric information (database) - to produce a geographically referenced database. Using 'hotlinks', the GIS may also allow the incorporation of raster images. The GIS software allows the user to collect, edit, analyze, and display this information. Geographic data is stored as

Points: location of electric and telephone poles, fire hydrants, energy installations, boreholes, traffic lights, etc.

Lines: data defined topologically in a network or linear structure, such as water pipelines, sewer systems, road center-lines, communication networks, etc.

Polygons: closed areas, each with is own distinct characteristics such as parcellation, land use, surface cover, structures, etc.

Georeferenced information stored in the system is organized in layers, or themes, each one belonging to a specific topological type and relating to a specific type of data. Examples of themes are a point theme of traffic lights, a line theme of street centerlines, or a polygon theme of land parcels. Some GIS software organizes information in the system as objects.

Input to the GIS may come from any number of sources and in different forms, according to the functional relations of the layer. Thus, data may be from aerial photographs, maps drawn to different scales, technical drawings, and textual material.

The process of setting up the GIS includes integration of the alphanumeric data, with graphical data using digitizers or scanners. Scanned images may be vectorized by appropriate software. It may also include field work, verification of the data and quality control.

A primary benefit of a GIS is that it integrates, in a generic manner, data and information that may be scattered throughout on organization, in different departments and on different documents. It can inherit properties from one layer to another without duplication of data. Poor accessibility of data prevents efficient management, planning, and operation, is wasteful of resources, and severely hampers the decision-making process.

GIS offers decision makers at various levels the capability of integrated and coordinated planning, efficient coordination of construction, and development of preventive and routine maintenance programs on the basis of reliable data and long-range plans. At senior management levels, GIS serves as an aid to policy definition and control of high priority and critical regions, and assists in decision making with respect to planning and development on different time horizons, and in the immediate, intermediate and long range.

GIS serves users on four levels:

Basic: archive or file for accessing up-to-date and reliable information on the various elements in the system.
Planning: accessing data for planning at all levels of detail, from conceptual planning to detailed design.
Management: decision making at all levels of management, from strategic to operational.
Aggregation of information for businesses.

Information above drawn from Advanced Geographic Information Systems Ltd. Can be reached @ agis@netvision.net.il

Error, Accuracy, and Precision in GIS

Database Conceptualization

GPS Explained

Back Home