Another way to find yourself
The ground-warning system that relies on digital maps is one of several ways that GPS technology can help airliners stay safely above the ground, says Thomas Brizendine, an analyst at the consulting firm Frost & Sullivan. Brizendine says it is so effective that, "there is no excuse for not knowing where you are, to within a centimeter in three dimensions, anywhere on planet Earth -- especially when GPS is coupled with other technologies." Still, he says, GPS is found only in a small percentage of commercial jetliners today.

Brizendine notes that the "vaults of the military, defense, aeronautic and electronics companies have many technologies developed for military applications that are viable and potentially useful in the commercial air sector, but for a variety of reasons, have not been implemented in civilian air fleets."

Another candidate for keeping jetliners in the air is an automated landing system that combines GPS with radar maps of terrain. In this system, the plane's navigational computer contains radar maps of terrain containing "markers" indicating mountains or large buildings that radar can easily identify. In flight, the GPS system approximately locates the plane, showing the computer where to look for the pre-set markers on the digital map. Finding the location from the radar map alone "would take extreme amounts of [computing] power," Brizendine says.

Tomahawk Cruise Missile by United States Navy.

"This system is one of many systems designed to enable automated landing for commercial air transport aircraft -- other systems use differential GPS, or inertial navigation systems (defined). The Tomahawk cruise missile, Brizendine observes, navigates with terrain-following maps and GPS coupled to an inertial navigation system. One way or another, an airliner could solve the problem of avoiding the ground by using GPS to locate itself in all dimensions, and a map to determine where the ground is, Brizendine says. "There is no technical reason that commercial aircraft should not know where the ground is at all times."

And achieving that millennium, he says, may not even call for a separate ground avoidance system, but rather for an upgrading of the navigation and mapping computer system. "The real solution is for a suite of redundant technologies, probably GPS, inertial navigation systems, database mapping, synthetic aperture radar" and other technologies that originated with the military. "With this set of technologies, aircraft will never again run into the ground by accident."

What if a pilot falls asleep by accident?

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