Geographic information system technology can be used for scientific investigations, resource management, asset management, archaeology, environmental impact assessment, urban planning, cartography, criminology, geographic history, marketing, logistics, and other purposes. For example, GIS might allow emergency planners to easily calculate emergency response times in the event of a natural disaster, GIS might be used to find wetlands that need protection from pollution, or GIS can be used by a company to site a new business location to take advantage of a previously under-served market.

A Geographic Information System (GIS) is a computerized marriage between a graphic representation and a textual description of a geographic location. A GIS provides the decision maker with a logical and graphic representation of geographically referenced information.
     
A GIS can maintain, analyze, and report on:
•    geographical data, such as points and symbols, lines and curves or polygons, attribute data, such as: characters, numbers or dates.
     
A GIS can provide accurate answers to geographic questions such as:
•    Where is a feature located?
•    What is it adjacent to?
•    What is its relationship to other features.
    
A GIS provides a powerful, logical, and intuitive means to store, manipulate, and retrieve data. It provides the ability to see on screen or in map form, only those features or objects that meet specific selection criteria. In an instant, you can visually identify features in a geographic representation that would take much longer to find in a printed report.

Data representation

GIS data represents real world objects (roads, land use, elevation) with digital data. Real world objects can be divided into two abstractions: discrete objects (a house) and continuous fields (rain fall amount or elevation). There are two broad methods used to store data in a GIS for both abstractions: Raster and Vector.
A raster data type is, in essence, any type of digital image represented in grids. Anyone who is familiar with digital photography will recognize the pixel as the smallest individual unit of an image. A combination of these pixels will create an image, distinct from the commonly used scalable vector graphics which are the basis of the vector model. While a digital image is concerned with the output as representation of reality, in a photograph or art transferred to computer, the raster data type will reflect an abstraction of reality. Aerial photos are one commonly used form of raster data, with only one purpose, to display a detailed image on a map or for the purposes of digitization. Other raster data sets will contain information regarding elevation, a DEM, or reflectance of a particular wavelength of light, LANDSAT.