Geographic Information Systems---Ann-Margaret Esnard,Nancy Sappington&Milton R.Ospina

  Geographic information system(GIS) is a tool that connects databases to maps.By combining a range of spatially referenced data and analytic tool,GIS technology enables people to prioritize issues,understand them,consider alternatives and reach viable conclusions.
  The capability of a GIS to link data sets together by common location information facilitates the sharing of information, such as interdepartmentally within an organization or via the internet with the public.
GIS COMPONENTS
The main components of a GIS are hardware, software,data sources,including metadata and data structure types.
Hardware
The hardware consists of a computer that meets the software system requirements and other equipment,such as printers,scanners or digitizers.
Software
GIS software provides the functions and tools necessary for storing,analyzing and displaying spatial information.
Data sources
To determine the type of data needed,one needs to first determine the types of produts a GIS will produce.
Metadata
Metadata are perhaps the most critical part of a GIS and often the most neglected.
Data types
There are two types of data: vector data and raster data. A GIS will integrate both types of data.
GIS FUNCTIONALITY
-Query by location
A query by location can be a search on a point within a polygon or a radius search from a specific point.
-Query by attribute
A query by attribute searches on data stored in the table.
-Boolean queries
Boolean queries are a combination of location queries and attribute queries.
-Buffers
A buffers is a region around a geographic feature or phenomenon.Buffers can be one ring or multiple rings.
-Address matching
This process matches the location of an event recorded as a street address,latitude and longitude position or milepost locations along a route in a table, to a street centerline,zip code or other administrative zone.
-Measuring distance
Distance can be measured as Euclidean distance,which is the distance of straight or curved paths.
-Overlays
The overlay operation is central to many GIS applications.
-Suitability analyses
Suitability analysis is commonly used for finding optimum locations for a project,based on a combination of map layers.