Generally speaking, GIS is a computer based technology, comprised of data, software, hardware and procedures that can be used to encode, store, correlate, analyze and display information about the earth's surface: what's on it; underneath it; what land is used for; and where natural resources, people and utilities are located.

The data in a GIS may be associated with a wide variety of applications, nevertheless all GIS data have one thing in common, they are in some way related to geographic position or location, which is the common element needed to correlate, integrate and spatially analyze the data.

A sound GIS environment requires three fundamental building blocks:

• A geodetic network to provide an accurate coordinate reference base;
• A digital topographic database to which other geographic data such as utility lines can be related;
• A digital land parcel map database against which land use, land ownership and a variety of demographic data can be referenced.

It is these building blocks to which the data in all GIS applications are referenced.

The rationale for any GIS is in its application to help users solve problems associated with their work. The building blocks mentioned above are all necessary components that have to be put in place before the development of the individual GIS applications begin.

If all applications developed, conform to one or more of these reference bases and associated standards, the data they contain can be correlated with any other data referenced to the same base. Thus the data collected by one discipline can be easily used by a variety of others when needed. This minimizes redundancy as the GIS data need only be stored by the agency that has the mandate to create it.

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