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available for civilian aircraft and surface navigation

• Computers that use data from the satellites to calculate a vehicle's location in a fraction of a second

•A digitized map, on which vehicle location data are displayed. The map is packed with information about airport facilities and hazards.

• An infrared camera that is so sensitive to body heat, it shows neck-ties and layers of clothing.

The system was developed by Gal-Scientific Corp., of Warminster.

The 10 year old firm, with 1997 revenues of $35 million, develops and markets fleet-tracking, aviation, training, and information technology Systems. The Global Positioning Satellites on which the system relies are not the same as the Galaxy 4 communications satellite that failed on Tuesday night,: leaving millions of people unable to use their paging services. The Galaxy 4 satellite is owned. by PanAmSat of Greenwich, The system in use at Philadelphia International Airport has the only tracking system approved for airport use by the Federal Aviation Administration, said Michele Engelhart, vice president in charge the Galaxy division, which produces the system.

It works like this:

Computers in rescue trucks analyze data from four or more of the satellites to calculate the vehicles' precise location, direction and speed of travel. That information is displayed on maps inside the vehicles and by computers on the airport's network. The control tower, which tracks aircraft with radar, flashes the precise location, or locations, of aircraft in distress to maps in rescue trucks and on the airport network. "In order to understand why this is important, you have to understand that the difference between our success and failure is measured in seconds," said Capt. Robert K. Wolfe, of the airport's rescue station. "People are dying from moment of impact, in various stages. If you're in seat 17-B and your leg is up at row 12... having me there 20 seconds earlier, to wrap a tourniquet around your leg and stop the bleeding means you live."

Just outside the office, near Terminal B, Brady and firefighter 'Francis Kehoe, in Foxtrot 2, one of the airport's three big, yellow rescue and firefighting trucks, began a demonstration of the technology. "If we get a real one, you'll have to go with us," Brady. said over the scream of a nearby DC9 airliner. A red symbol of an aircraft flashed on the screen in front of him, in the right seat. It was shown as being near the Federal Express terminal, off the far end of Runway 27 Right, one of the two main parallel runways. Foxtrot 2's location was indicated by an elongated triangle, Pointing in its direction of travel. The huge all-wheel-drive truck lumbered along at Well below its 60-M.P.H. cruising speed weaving cautiously among taxiing airliners.

The message next to the map said the troubled airplane was a three engine Boeing 727, with 136 souls (aviation parlance for people) and 35,000 pounds of fuel on board. The message also gave the wind's direction and speed, and precise elevation of the accident. With the risk of hazardous fumes and flammable liquid, rescue crews "like to approach with wind at their back and from uphill of the incident," Wolfe had explained earlier.

The infrared camera mounted atop truck cab was displaying a picture op a screen just above the windshield. In a real crash on a foggy day or in a snowstorm, the driver could glance up at it from time to time and spot people and flaming debris not visible to the human eye. "There could be bodies or wreckage strewn all over," Brady said a camera, which detects the warmth of bodies or the heat of flames, you can see them ... the last thing we want to do is cause more injuries. The 727, in this instance, turned out to be a parked U.S. Postal Service cargo aircraft. As Foxtrot 2 approached, Brady demonstrated how tapping a button confirms the accident location - the map symbol changes from red to blue. He tapped another button, marked ambulance, and a blue cross appeared on the map. It also appeared on a map in the control center. In a real crash, an ambulance or helicopter, also guided by GPS, would have been dispatched to that spot.

He tapped yet another button to mark the location of a dead body, another to mark a piece of wreckage, another to mark a damaged safety device. Each tap instantly sends to the command center precise information that is recorded for crash investigators.

With the Delaware River flowing around three sides of the airport, "if we have a major incident, there's a 50-50 chance it going to be a wet one," Wolfe said. So the airport fire station maintains a 30 horsepower, high-speed rescue boat that can be in the water in seconds and deliver eight 20 passenger rafts to the scene. At night and in bad weather, the GPS and infrared camera equipment will shave lifesaving minutes off the time it takes to get boats and helicopters to a crash scene, he said. All that won't be used just in disasters, which the Philadelphia airport rarely has the last fatal airliner accident here, in which six died was in 1951.

About 150 times a year, there's an alert. Sometimes it is a faulty warning light that makes a Pilot wonder whether the landing gear is down. Other times it is a false fire alarm or potential problem spotted by an air traffic controller.

With the infrared camera, "we'll be able to detect quickly if there's a fire in a plane's cargo area, and precisely where it is," and that will help with the evacuation."

The system will also help with maintenance of the nation's fastest growing airport, which last year handled 22.4 million passengers and 466,692 takeoffs and landings. Fifty miles of critical security fence and 100,000 safety items, ranging from the runway surface to 8,000 essential light bulbs, must be inspected daily and repaired immediately, said Sam Mason, the point person developing the new system.

With the new system, repair orders could list the precise location of a burned-out runway light or washout under a fence, and GPS could guide repair crews directly to where there's work to do.

The cost of the system, to be paid with fees from airlines and passengers. will depend on the numborof vehicles equipped, which has not been determined.

"Once you get a tool like this, you start to think, envision and collaborate on what else can we do with this, (Aviation Facility Manager, Marc) Liciardello said, "and we've only just begun to do that."