Civilians turning to positioning devices Applications of GPS go beyond military

March 16, 1997|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

Salesmen lost in Peoria, hikers disoriented in Utah, and fishermen trying to return to where the Big One got away are turning more and more to Pentagon satellites for directions.

The federal government's $12 billion Global Positioning System (GPS), once the preserve of military commanders, is increasingly accessible to the public and has begun reshaping the way people play, travel and work.

Officials at the Department of Defense and the Department of Transportation agreed last month to make the military's more accurate but long-restricted "L2" GPS signals accessible for civilian use. It was the latest government concession to the burgeoning commercial demand for better satellite navigation.

"Knowing where you are, where you are going and how to get there are becoming more and more important and useful," said George S. Fry, president of Aviso Micro Technology Co.

In a recent market research study for Forward Concepts of Tempe, Ariz., he estimated the worldwide market for civilian GPS technologies at about $2.5 billion in 1996, and $9.6 billion by 2000.

Completed just three years ago, the GPS system uses 24 satellites that orbit the Earth every 12 hours. They continuously transmit coded signals and time data that receivers use to compute latitude and longitude.

Already familiar to aircraft pilots and ship captains, GPS devices are turning up in rental cars and outdoors stores. Falling prices for the basic devices have encouraged more than 100 manufacturers to begin inventing and building new consumer applications.

At the Wild Wing Plantation -- a 72-hole golf resort at Myrtle Beach, S.C. -- head golf pro Tim Tilma needed something to distinguish his courses from nearly 100 others in the area. He chose a cart-mounted GPS system that tells players how far they are from the pin, helping them choose the proper club.

The system, ProShot, also gives golfers other tips on how to play the hole as they move down the fairway. "It's like an automated caddy," Tilma said.

In his pro shop, a computer map shows the position of every cart on the course. When a foursome lags, the computer alerts Tilma, who sends the players a message suggesting they pick up the pace.

This is not what the Defense Department envisioned when it began building the GPS system in the mid-1970s. Military planners wanted a satellite-based navigation system that would provide U.S. forces with secure, all-weather positioning data anywhere on the planet.

The GPS satellite network, built by Rockwell, was completed three years ago. It works much as our eyes and brain do as we walk down the street.

Signals received by your eyes tell you how far you are from the traffic on your right, the shops on your left and the "Don't Walk" sign up ahead. Your brain interprets all the data and tells you that you're still safe on the sidewalk.

In the same way, a Global Positioning System receiver repeatedly calculates its position relative to the known positions of three or more GPS satellites orbiting 12,000 miles above the Earth. That information is calculated from data contained in the signals broadcast by each of the satellites.

It's a bit like identifying the one city that's 100 miles from Philadelphia, 60 miles from Frederick and 40 miles from Washington. It could only be Baltimore.

At least eight satellites are "visible" 85 percent of the time from nearly anywhere except polar regions. That's enough to do the ** job even if some signals are blocked by buildings or trees.

A GPS receiver only listens. It sends no signals to the satellites. That keeps the receivers small and gives the system unlimited capacity -- just as every car and pedestrian can have a radio that receives broadcast signals.

Kirk Singer, president of Backcountry Experience in Durango, Colo., sells GPS receivers to people headed for the wilderness.

"It is absolutely growing in popularity because four years ago the pricing was in the mid-$500 to $800 range," he said. Today he can sell a receiver for as little as $160.

Most of the 40 he sold last year went to hunters and backpackers. "My wife's father has one strapped to his ATV [all-terrain vehicle] when he goes elk hunting," he said.

GPS-users still need a good compass and maps with latitude and longitude grid lines. Singer recalled one adventurer in central Colorado who forgot his map.

"He knew where he was because the GPS said he was 'Here.' But he had no idea where 'here' was," Singer said. "So he had to call the sheriff on his cell phone. The guy gave his coordinates so the sheriff could [consult a map and] figure where the guy was."

Most trail maps still don't show latitude and longitude lines. But thanks to falling GPS prices, demand has risen "dramatically" in the past two years, said Tom Carley, sales manager for Trails Illustrated, a map publisher in Evergreen, Colo.

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