(FORTUNE Magazine) – WHEN Frank St. Onge, manager of marketing analysis for Osram/Sylvania, really wants to impress customers -- the wholesalers who distribute his company's lamps, for instance -- he brings them into the high-tech ''War Room'' at headquarters in Danvers, Massachusetts, dims the lights, and turns on the equipment. The room is designed for teleconferencing and state-of-the-art multimedia presentations, but what most lights up visitors are the maps -- big computerized ones, rich with useful data, displayed on a six-foot color videoscreen. Says St. Onge: ''We show them where are our competitors, where are the customers, and what areas of the country have the greatest sales potential, down to the block level. We show how many specialty lamps different hospitals in their region buy. Of course, we could give them the same data on reams of spreadsheets, but illustrating the information with a map is a much more powerful tool.'' Behind this sensory approach to winning customers is a geographic information system (GIS), a computer setup that makes it possible to view and analyze data on digitized maps. GIS isn't new: Utilities, oil companies, and governments have long used such systems to plot transmission routes, manage natural resources, and track pollution; the technology already accounts for $2.1 billion a year in hardware, software, and consulting sales. But the cost of GIS has fallen so dramatically in recent years that GIS is now on the verge of becoming one of the hottest business information tools. Companies as diverse as Cigna, Sears, Super Valu, the Gap, and Isuzu have adopted mapping as a down-to-earth way to interpret data that were previously available only in the form of numbingly complex printouts, spreadsheets, and charts. Says Jack Dangermond, founder of ESRI, the Redlands, California, company that pioneered GIS technology using mainframe computers in the 1970s: ''A map offers an intuitive way to organize things. People remember things about space that they don't about any other way of organizing information.'' A GIS today typically consists of a demographic database, digitized maps, a computer, and software that enables the user to add corporate data to the mix. The cost of bringing together these elements has dropped from $125,000 per user in 1985 to around $35,000, according to John Antenucci, who heads a GIS consulting firm in Frankfort, Kentucky. That's largely because desktop computers have become powerful enough to manage and analyze the masses of data that mapping involves. A host of startup companies have emerged to offer low- cost, business-focused mapping data and software. Wessex of Winnetka, Illinois, sells a complete set of U.S. street maps and census information for $995; the old cost for similar data was over $50,000. Powerful GIS programs can be had for $2,500 or less from Strategic Mapping of Santa Clara, California; MapInfo of Troy, New York; and Tactics International of Andover, Massachusetts, which makes Tactician, the program Osram/Sylvania depends on. For St. Onge, computer mapping is one of the best ways to take advantage of the ''source,'' as he calls the marketing database of the nation's No. 2 light-bulb maker (General Electric is No. 1). Like every corporate database, Sylvania's is loaded with geographic information, such as addresses of customers. St. Onge taps into the mainframe with a Hewlett-Packard 486 PC and two Apple Macintoshes equipped with a custom version of Tactician. He uses the system not just to woo distributors but also to support his sales staff. To persuade a store owner to allot shelf space to Sylvania lamps, for example, a sales rep will present a demographic map of the store's clientele within a ten-mile radius, along with information about their bulb-buying habits. Reps also get color-coded ''hot-cold'' maps of their territories, which highlight neighborhoods where lamp use is likely to be most intense. While business programs account for only 6% of the $630-million-a-year market for GIS software, they are its hottest segment. Kathryn Hale, an analyst at Dataquest in San Jose, California, reports that purchases of marketing and sales mapping programs have more than tripled since 1990. She ! figures such spending will reach $200 million a year by 1997 as businesses increasingly turn to GIS to keep pace with competitors. How can you stay ahead of the trend? Here are some of the most successful and widespread uses of GIS:

-- Site selection. If your company is expanding, it is probably using GIS to plot new locations. Says Brady Foust, a consultant in Eau Claire, Wisconsin: ''Stores succeed or fail because of location. Only GIS can tie together diverse locational information and make sense of it.'' Lately Foust has worked with an upscale clothing chain (he won't name it) that has stores in Eau Claire and Green Bay. Using Strategic Mapping's Atlas software, he analyzed sales data and showed on a map of central Wisconsin how each store drew most of its customers from within a 20-mile radius. Between the sites lay a wide swath where fewer than 15% of would-be customers visited either store. Foust's conclusion: A single new store in the town of Wausau would let the retailer sell effectively across the entire state. Super Valu, the nation's largest supermarket wholesaler, bought Strategic Mapping software last April to help pick sites. Perry Harrison, director of market analysis, says his staff used to spread paper maps of prospective sites across a room and then painstakingly compare those with scrolls of demographic data. Now the information is concentrated on the screen of a Compaq 486. Says Harrison: ''GIS frees up our analysts so they can actually analyze.''

-- Target marketing. Western Auto, a Sears Roebuck subsidiary, uses Tactician on IBM PCs and Apple Macintoshes to choose store locations. But the real edge is gained in fine-tuning a new store's inventory. Integrating company data with information from market researchers like R.L. Polk, Western Auto creates a detailed demographic profile of the neighborhood. That lets the store tailor its offerings to, say, lower-middle-class do-it-yourselfers who prefer to fix their own brakes, or upscale types who mainly want polishes and accessories. Says Tom Swiontek, the Sears planning manager who helped develop the GIS: ''We set up the right product mix right away and as a result build up the clientele much faster.'' It now takes six months for the average Western Auto outlet to break even on operating expenses, down from 18 months before the GIS. American Isuzu runs a GIS from Strategic Mapping on AST Research 486 PCs to shape its marketing plans. This summer two Isuzu dealers in Yakima and Pasco, Washington, offered weekend-long test drives of Trooper, a luxury sport- utility vehicle. Director of strategic planning Mark Darling used the GIS to create a list of likely customers near the dealers. The response rate was 18%, high for a direct-mail campaign. Better yet, sales are up: The Pasco dealer, who had sold four Troopers in the first half of the year, sold four more in August alone.

-- Sales support. At Cigna, the giant insurer, a GIS helps salesmen pitch managed-care plans to brokers who buy health policies for corporations. A broker might ask, for instance, what percentage of his client's employees will find at least two Cigna-affiliated doctors within eight miles of their homes. Whereas the salesman formerly would have presented many pages of tabular data in response, he now provides the broker with maps showing the distribution of physicians and employees. The GIS, a $35,000 setup that includes Strategic Mapping software and a souped-up IBM PC, also performs statistical analysis, yielding such details as average distance from employee to provider. Marina Pye, a Cigna sales support supervisor until she left recently for another job, started offering the maps in early 1992. At first, she says, sales reps used maps only to embellish major presentations; now ''they wish we could map 24 hours a day. Initially we did 15 cases per month, but now we're up over 100.''

-- Network analysis. Whether your network consists of sales offices spread across a region or ambulance services in a city, GIS can find its weak spots. At PacTel, a subsidiary of Pacific Telesis, director of network information technology Jerry Sprecher uses a high-powered GIS to display locations where the company's cellular signals peter out. The system, which runs on Sun Microsystems workstations, combines street maps, locations of cellular transmitters, and 3-D representations of local topography based on satellite data. It lets Sprecher show, for instance, where a subscriber driving up Interstate 80 into the Sierra Nevada will lose his connection -- and where PacTel should put more transmitters.

-- Disaster management. Insurance companies are finding that GIS helps them serve customers faster when disaster strikes. During Hurricane Andrew last year, ITT Hartford used MapInfo software to track the storm's attack on the Florida coastline. The company was able to determine which zip codes would be most affected, who its policyholders were in those areas, and how much in damages it might have to pay. The analysis helped it dispatch adjusters quickly to the hardest-hit neighborhoods.

-- Fleet management. Yellow Freight Systems of Overland Park, Kansas, is one of many transportation companies that depend on elaborate GIS setups to manage huge vehicle fleets. Yellow has a hub system like those run by airlines; operations planning coordinator Ken Peck needs a network of 31 Sun workstations equipped with ESRI software to keep track of 3,700 trucks traveling more than 640 million miles a year. Before the GIS was installed, the chore of defining delivery zones for each of 600 terminals was left to a secretary, who used a Rand McNally atlas and Magic Markers. Not surprisingly, scheduling was less than efficient. Peck's GIS does a better job, allowing for such factors as speed limits and the number of loading docks at terminals in determining the zones. The system lets Yellow supply customers with up-to-date maps that divide the U.S. into one-day, two-day, and other zones, and show how long a shipment will take.

-- Regulatory compliance. Utilities and banks are natural users of GIS technology because laws govern the way they serve their regions. Norwest Corp., a Minneapolis bank with $48 billion in assets, is setting up a GIS intended, among other things, to help it obey the 1977 Community Reinvestment Act and other laws that prohibit racial discrimination in lending. Says Karen Alnes, director of community reinvestment programs: ''We'll use the system to look at where our loan applications come from, where we are making our approvals and denials, and to identify patterns as required by law. It's a vast improvement over putting pins in a map, which is essentially what we've done up to now.'' Consumer watchdog groups have already become sophisticated in using GIS to monitor mortgage lending. Essential Information, a nonprofit founded by Ralph Nader in 1979, recently used a system donated by ESRI to analyze government data on 1.3 million home purchase loan applications received by banks and mortgage companies in 16 cities. The resulting maps vividly show the difference between the behavior of most banks and that of mortgage companies less constrained by federal lending laws. One set of maps, for example, superimposes the 1991 lending in Los Angeles by Sears Mortgage Corp. and Great Western Bank on a map of the city that has been highlighted to show minority neighborhoods. Instantly apparent: Lightly regulated Sears made far fewer loans in those neighborhoods than heavily regulated Great Western. While Sears's share of the home lending market in white neighborhoods was 4% in 1991, it held less than 0.3% of the loans made in minority neighborhoods. Great Western, on the other hand, had a share of 4.7% in white neighborhoods and fully 16.9% in minority neighborhoods. ON THE HORIZON are potent new applications that marry computer maps with signals from global positioning satellites (GPS). The signals enable any vehicle equipped with a receiver to pinpoint its location as it moves. Eventually GIS and GPS could transform aviation and shipping -- and even agriculture, if Donald Larson can realize his vision. An Iowa farmer with technological know-how, Larson has worked with tractor manufacturers on a system that brings some scientific accuracy to the process of mixing and spreading chemical fertilizer. Traditionally, soil samples are drawn from different locations in a field, the results are averaged, and one mix of chemicals is spread across the entire field. The problem is that soil quality varies, and not all parts of a field should get the same dose of fertilizer. The software unites a GPS receiver right on the tractor with a Compaq PC showing a computerized map of the field and its various types of soil. As the tractor's position is continually updated, the PC makes sure the right amount of the fertilizer is dispensed. The system primes the field for maximum yield and reduces harmful runoff because low-producing acres don't get too much fertilizer. Larson says Deere and other tractor giants are ''looking into'' the technology; AgChem, a Minnesota manufacturer, already sells a similarly equipped tractor. GIS is on its way to becoming a standard business tool. Within the next decade, mapping software will almost certainly find its way onto your PC -- and you probably won't even think of it as a GIS when it arrives. Joe Francica, senior marketing manager at Intergraph, a leading provider of high- end GIS programs, believes that maps will soon serve as an integral part of other software, just as spreadsheets do today: ''If you look at successful personal finance programs like Quicken or Microsoft Money, the guts of those programs are spreadsheets. As has happened with spreadsheets, GIS will become an embedded technology.'' Mapping functions have already started to show up embedded in database software sold by companies such as OneSource Information Services, a Lotus Development spinoff. AST Research now includes mapping software with some of its machines. The mapping industry recognizes this trend. The editors of its newest trade magazine, which first appeared nine months ago, rejected the idea of having the GIS acronym anywhere in the title. Instead, they opted for Business Geographics. As more and more companies are discovering, business geographics is fast becoming a business necessity.