EVERY work day, police officer Michael Byers takes eight colored
pencils and draws on a map of Durham, N.C.
He is tracking major crimes. If the procedure seems a little
archaic ("something right out of caveman," Officer Byers laughs),
the idea makes sense. Each crime has its color. By pinpointing when
and where the crimes occurred, officer Byers hopes to spot patterns
Add the power of a computer (as Durham soon will) and the process
becomes a geographic information system or GIS.
Mike Watson, chief appraiser of the Bell County (Texas) Tax
Appraisal District, knows what GIS can do. For years, his office
used big paper maps to track property ownership and value. When the
county installed a GIS system a few years ago, he and his colleagues
were surprised to discover land they never knew existed before. Some
plots had been overlooked and gone untaxed for years. Meanwhile, the
appraisers found that other plots fully described and collecting
delinquent taxes didn't exist at all.
GIS is a simple idea.
"You have used GIS all your life," says Richard Pabst, manager of
GIS solutions for IBM's Mid-Atlantic area. For example, some-one
wanting a tennis racket might look up sporting goods in the Yellow
Pages, find a store's address, then use a map to find how to get
That's GIS, Mr. Pabst says. "You took some information and an
objective and tied them to together."
A computer usually does this by digitizing a paper map or aerial
photo (turning it into a series of dots, lines, and spaces that the
computer can display). Each dot, line, or space is linked to pieces
of information stored in the computer. So, a dot might represent the
number of people living at that coordinate, their age, or their
income. A line on a road map might be tied to data identifying it as
a paved road, a superhighway, or Interstate I-70.
A paper map might show some of these details. GIS allows people
to play with all the variables and ask sophisticated questions. For
example: Show all the places in California where most of the
residents are at least 50 years old, earn between $35,000 and
$50,000, and have bought a car in the last 18 months.
GIS computer systems have been around for more than 20 years. In
the early '70s, utilities began using the technology to track
maintenance and react to problems on its power lines. Those early
systems required expensive mainframe computers and software. As
hardware and software costs have come down, more businesses are
looking at GIS for all sorts of uses.
In a large room of an IBM facility here in Raleigh, N.C., company
officials show how one of their IBM PS/2 desktop machines might
handle a retail store marketing decision.
The screen displays the location of a store and all its
competitors in the area. The retailers wonder whether they should
move to a new location. …