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><A
NAME="WHATISGIS"
>1. What is a GIS?</A
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><P
> There are many ways to describe a Geographic Information System. Here
are three working definitions (from David A. Hastings, 1992, Geographic
Information Systems: A Tool for Geoscience Analysis and Interpretation):
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> (The minimal definition): A GIS is a hardware/software system
for the storage, management, and (with hardcopy or screen
graphic) selective retrieval capabilities of georeferenced data.
Definitions like this one are often used by vendors and users of
vector-only GIS, whose objective is sophisticated management and
output of cartographic data.
</P
></LI
><LI
><P
> (A parallel definition): A GIS is a hardware/software system for
managing and displaying spatial data. It is similar to a
traditional Data Base Management System, where we now think in
<I
CLASS="EMPHASIS"
>spatial</I
> rather than in tabular terms, and where the
"report writer" now allows output of maps as well as of tables
and numbers. Thus we can consider a GIS a "spatial DBMS" as
opposed to traditional "tabular DBMSs." Few people use this
definition, but it might help to explain GIS to a DBMS user.
</P
></LI
><LI
><P
> (A more aggressive 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 GISs that go beyond cartographic approaches.
</P
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><P
> Another definition can be found at
<A
HREF="http://www.geo.ed.ac.uk/home/research/whatisgis.html"
TARGET="_top"
><I
CLASS="CITETITLE"
>the University of Edinburgh.</I
></A
>
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