Air Transport World

Global Positioning System civil use likely; but problems linger.

A navigation system that at the flick of a switch can pinpoint a position within 100 meters at any spot on the globe will be available to the world civil aviation community in about four years. In addition to this high precision positioning information, this new system also will supply highly accurate altitude and speed data.

The Global Positioning System is a U.S. military designed system using earth-orbiting satellites, formerly known as Navstar/GPS. What is certain about GPS is that the basic military system will be in full operation in 1988--it tested out to meet or exceed expectations and Congress appropriated the money to buy the satellites.

Questions as yet unresolved for potential civil users include how much confidence can be placed on GPS and how many of its services can be utilized. Naturally, the eternal questions of price--how much and who pays--remain to be settled.

FAA's principal concerns about extensive civil use of GPS center on the system's coverage and signal reliability. The hot potato of civil user fees seems to be fading from view, but the determination of system costs to the civil community and the prospect of government efforts to recoup those costs still bother potential U.S. users.

Throughout the military development of GPS the potential for civil use has been clouded by a series of policy disputes.

The initial point of contention was military reluctance to give civil users access to high accuracy GPS signals. Department of Defense (DOD) for years insisted that civil uses would have to be content with an accuracy of 500 meters, even though DOD users will have access to 15-meter accuracy, good enough for precision approaches without ground-based aids.

After a long battle with FAA, Department of Transportation and various user groups, DOD relented. Last June, one month after Congress agreed to spend $1.17 billion for the GPS satellites, DOD agreed to give civil users access to 100 meter accuracy.

While the accuracy battle was being fought civil users suffered a setback on another front. …

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