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What is GIS? A Geographic Information System (GIS) is a computerized
mapping process for developing, maintaining, and using electronic
information about the world around us. A GIS can handle many types of
information, from data about physical map locations to names, numbers
and relationships linked to physical places. The key is that all
information in a GIS is geo-referenced, meaning that all information is
associated with unique map coordinates that correspond to actual places
on the earth. When you query a GIS computer about a
particular place you are able to access all the information linked to
that place, both in number (database) and picture (map) format. Very
specific definitions of geographic information systems are available,
and two are offered below.
Bruce Gittings, a professor in
the Department of Geography at the University of
Edinburgh, offers the following definition of Geographic Information
Systems:
Geographical Information
Systems (GIS) can be regarded as the high-tech equivalent of the map. An
individual map contains a lot of information which is used in different
ways by different individuals and organizations. It represents the means
of locating ourselves in relation to the world around us. Maps are used
in diverse applications; from locating telephone wires and gas mains
under our streets, to displaying the extent of de-forestation in the
Brazilian Amazon.
The map has been in existence
in much the same form for thousands of years. In the
traditional form it suffers from a number of problems. Firstly maps are
static and therefore difficult and expensive to keep up to date. This
relates to a second problem, in that because they are static they lose
flexibility, for example maps exist as discrete sheets and inevitably
your area of interest lies on the corner of four adjacent sheets. In
addition maps are often very complex and may require an expert to
extract the particular data which are of interest.
GIS provides the facility to
extract the different sets of information from a map
(roads, settlements, vegetation, etc.) and use these as
required. This provides great flexibility, allowing a paper map to be
quickly produced which exactly meets the needs of the user. However, GIS
goes further, because the data are stored on a computer, analysis and
modeling become possible. For example, one might point at two buildings,
ask the computer to describe each from an attached database (much more
information than could be displayed on a paper map) and then to
calculate the best route between these.
David A. Hastings, in his 1992 book
Geographic Information Systems: A Tool for Geoscience
Analysis and Interpretation, offers a more technical
definition:
A GIS is a system of
hardware, software, and data that facilitates the
development, enhancement, modeling, and display of multivariate (e.g.
multilayered) spatially referenced data. It performs some analytical
functions itself, and by its analysis, selective retrieval and display
capabilities, helps the user to further analyze and interpret the data.
Properly configured, the GIS can model (e.g. synthetically recreate) a
feature or phenomenon as a function of other features or phenomena which
may be related - where all features or phenomena are represented
(characterized) by spatial and related tabular data. The analytical
objectives described here are sometimes controversial - and often given
lip service by cartographic GIS specialists who have not yet seen what
can be accomplished scientifically by a select few GIS's that go beyond
cartographic approaches.
For additional information on
GIS please visit "The CyberInstitute Short-Course on
Geographic Information Systems," compiled by David
Hastings on the National Oceanic and Atmospheric Administration's
National Geophysical Data Center web page at http://www.ngdc.noaa.gov/seg/tools/gis/referenc.shtml
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