A Geographic Information System, or
GIS, is an organized collection of computer
hardware, software, geographic data, and personnel designed to efficiently capture, store,
update, manipulate, analyze, and display all forms of geographically referenced
information. Or, in simple terms:
A computer system capable of
holding and using data describing places on the earth's surface.
Many computer programs, such as spreadsheets, statistics
packages or drafting packages can handle simple geographic or spatial data, but this does
not necessarily make them a GIS. A true GIS links spatial data with geographic information
about a particular feature on the map. For example, the centerline that represents a road
on a map doesn't tell you much about the road except its location. To find out the road's
width or pavement type, you must query the database. Using the information stored in the
database, you could create a display symbolizing the roads according to the type of
information that needs to be shown.
In short, a GIS doesn't hold maps or pictures - it holds a
database. The database concept is central to a GIS and is the main difference between a
GIS and drafting or computer mapping systems, which can only produce a good graphic
output. All contemporary geographic information systems incorporate a database management
A GIS gives you the ability to associate information with a
feature on a map and to create new relationships that can determine the suitability of
various sites for development, evaluate environmental impact, identify the best location
for a new facility, and so on.
A GIS is a very powerful tool that can be used to capture,
store and analyze geographic data but it is not, by any means, a stand-alone system. You
need several other very important components to make up a GIS:
Without well trained, competent personnel operating and
supporting a GIS the system would not function. Skill in selecting and using tools from
the GIS toolbox and an intimate knowledge of the data being used are essential to your
success as GIS user. Just pressing a button is not enough.
Volusia County GIS personnel
Currently the GIS network within Volusia County consists of
numerous workstations, X-stations, PCs, printers and plotters. The system is driven by a
RISC 6000 model H50 server with 1 GB of RAM and 95 GB of disk space.
Volusia County GIS hardware
In order to use a GIS in the most efficient manner it is
important to run the most up-to-date version of the software that is available. At this
time, Volusia County is running IBM AIX 4.3, ArcInfo Version 8.0.2, and ArcView 3.2.
Volusia County GIS software
The heart of any GIS is the database through which
questions such as what a feature is, where it is, and how it relates to other features can
be answered. The Volusia County digital map library is designed to allow any user on the
GIS network to view county wide geographic data from a common source. The map library also
provides an efficient and secure means of maintaining the database.
Volusia County's GIS data
Questions a GIS can answer
Perhaps the simplest way to define a GIS is by listing the
types of questions it can answer. For any application there are five generic questions
that a sophisticated GIS can answer.
1. Location: What is at a given
The first of these questions seeks to find out what exists
at a particular location. A location can be described as a place name, zip code or
2. Condition: Where does something
Using spatial analysis the second question seeks to find a
location where certain conditions are satisfied (e.g., an unforested section of land at
least 2,000 square meters in size, within 100 meters of a road, and with soils suitable
for supporting buildings).
3. Trends: What has changed since
The third question might involve a combination of the first
two and seeks to find the differences within an area over time.
4. Patterns: What spatial patterns
You might ask this question to determine whether cancer is
a major cause of death among residents near a nuclear power station. Just as important,
you might want to know how many anomalies there are that don't fit the pattern and where
they are located.
5. Modeling: What if ...?
"What if ..." questions are posed to determine
what happens, for example, if a new road is added to a network. Answering this type of
question requires geographic as well as other information.
GIS is not......
.....simply a computer system for making maps, although it
can create maps at different scales, in different projections, and with different colors.
A GIS is an analytical tool. The major advantage of a GIS is that it allows you to
identify the spatial relationship between map features. A GIS does not store a map in any
conventional sense; nor does it store a particular image or view of a geographic area.
Instead, a GIS stores the data from which you can draw a desired view to suit a particular
Glossary of common GIS terms