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A geographic
information system (GIS) is a computer-based tool for mapping and
analyzing things that exist and events that happen on earth. GIS
technology integrates common database operations such as query and
statistical analysis with the unique visualization and geographic
analysis benefits offered by maps. These abilities distinguish GIS
from other information systems and make it valuable to a wide range of
public and private enterprises for explaining events, predicting
outcomes, and planning strategies.
The major
challenges we face in the world today--overpopulation, pollution,
deforestation, natural disasters--have a critical geographic
dimension.
Whether
siting a new business, finding the best soil for growing bananas, or
figuring out the best route for an emergency vehicle, local problems
also have a geographical component GIS will give you the power to
create maps, integrate information, visualize scenarios, solve
complicated problems, present powerful ideas, and develop effective
solutions like never before. GIS is a tool used by individuals and
organizations, schools, governments, and businesses seeking innovative
ways to solve their problems.
Mapmaking
and geographic analysis are not new, but a GIS performs these tasks
better and faster than do the old manual methods. And, before GIS
technology, only a few people had the skills necessary to use
geographic information to help with decision making and problem
solving.
Today, GIS
is a multibillion-dollar industry employing hundreds of thousands of
people worldwide. GIS is taught in schools, colleges, and universities
throughout the world. Professionals in every field are increasingly
aware of the advantages of thinking and working geographically.
How GIS Works
A GIS stores
information about the world as a collection of thematic layers that
can be linked together by geography. This simple but extremely
powerful and versatile concept has proven invaluable for solving many
real-world problems from tracking delivery vehicles, to recording
details of planning applications, to modeling global atmospheric
circulation.
Geographic References
Geographic information contains either an explicit geographic
reference, such as a latitude and longitude or national grid
coordinate, or an implicit reference such as an address, postal code,
census tract name, forest stand identifier, or road name. An automated
process called geocoding is used to create explicit geographic
references (multiple locations) from implicit references (descriptions
such as addresses). These geographic references allow you to locate
features, such as a business or forest stand, and events, such as an
earthquake, on the earth's surface for analysis.
Vector
and Raster Models
Geographic information systems work with two fundamentally different
types of geographic models--the "vector" model and the "raster" model.
In the vector model, information about points, lines, and polygons is
encoded and stored as a collection of x,y coordinates. The
location of a point feature, such as a bore hole, can be described by
a single x,y coordinate. Linear features, such as roads and
rivers, can be stored as a collection of point coordinates. Polygonal
features, such as sales territories and river catchments, can be
stored as a closed loop of coordinates.
The vector
model is extremely useful for describing discrete features, but less
useful for describing continuously varying features such as soil type
or accessibility costs for hospitals. The raster model has evolved to
model such continuous features. A raster image comprises a collection
of grid cells rather like a scanned map or picture. Both the vector
and raster models for storing geographic data have unique advantages
and disadvantages. Modern GISs are able to handle both models.
 Typical
Uses for GIS
Local
Government
Planning/building control; land searches; boundary change modelling;
property/highways maintenance; crimes analysis; police/fire service
command and control.
Health
Care
Asset management; ambulance routeing/mobilisation; epidemiological
studies; road traffic accident analysis.
Financial
Service
Branch location assessment and analysis; facilities management;
demographic profiling; target marketing; insurance claim/risk modeling
and analysis.
Retailing
Store location assessment and analysis; inventory and facilities
management; deliveries routeing; drive-time studies.
Agriculture
Crop monitoring; land use management; commodity forecasting; soil
studies; irrigation planning and water resource assessment.
Transportation
Infrastructure planning/lifecycle management; Electronic Chart Display
Information Systems (ECDIS); integrated transport planning; vehicle
navigation.
Utilities
Network/capacity/maintenance planning; asset management; base map
generation; customer records; market analysis; leak detection/fault
location; environmental impact studies; safety monitoring.
Environment
Pollution/weather/climate monitoring; cause-effect studies; landscape
assessment; conservation planning; biodiversity libraries.
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