Trimble GPS Tutorial - Navigation

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DGPS?

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Flying a single-engine Piper Cub or a commercial jumbo jet requires the same precise navigation information, and GPS puts it all at the pilot's fingertips as safely as possible.

By providing more precise navigation tools and accurate landing systems, GPS not only makes flying safer, but also more efficient. With precise point-to-point navigation, GPS saves fuel and extends an aircraft's range by ensuring pilots don't stray from the most direct routes to their destinations.

GPS accuracy will also allow closer aircraft separations on more direct routes, which in turn means more planes can occupy our limited airspace. This is especially helpful when you're landing a plane in the middle of mountains. And small medical evac helicopters benefit from the extra minutes saved by the accuracy of GPS navigation.

Where the Runway Meets the Mountains

As if landing an airplane wasn't demanding enough, the airport at Juneau, Alaska has an extra challenge. It's surrounded by glacier-covered mountains. And if you miss your first approach there's no way out except the way you came in since there's a 3,000-foot peak just beyond the end of the runway. But when Trimble, working with the FAA, set up a test of a Differential GPS navigation system, it helped the pilots tame the mountains and land safely.

The mountains have hindered the use of traditional ILS (Instrument Landing Systems) since they obstruct radio signals. But the DGPS installed at the airport and on five specially equipped aircraft now allows pilots make their approach with bulls-eye accuracy. Layton Bennett, owner of L.A.B. Flying Service, which has a DGPS receiver installed in one of his aircraft, reports "Our pilots say it's more accurate than anything they've ever flown."

DGPS corrects the signal degradation that is common with standard GPS, and provides 2 to 3-meter lateral accuracy and 3 to 5-meter vertical accuracy at the airport. The Juneau test also proves the reliability of the GPS signal at high altitudes, which is not the prime focal area of the GPS signal footprint. Even better, the precise position information provides controllers in the tower with a real-time pictures of the landing aircraft. A two-way data link sends the plane's location back to the tower where it's displayed on a computer monitor.

The ultimate goal of the Trimble/FAA project is to prove the reliability, accuracy and safety of DGPS and certify it for Class 1 commercial landings. So far, the operation of the system has been flawless and the results very encouraging. This is one test that GPS passed with "flying" colors.

Get Me to the Hospital On Time

When you're flying a critical patient to the hospital might not always follow standard routes and predetermined schedules. That's why the University of Wisconsin Hospital and Clinics knew the issue of navigation would be critical for FAA approach approval to their landing pad. And that's why they put a Trimble GPS-based landing system to work.

"Time is crucial when you're trying to save lives," says John McCarthy, Training Officer for Corporate Jet's Air Medical Services Division. "Trimble's 2101 GPS navigation system allows us to perform our jobs more efficiently and safely. Its operation has been flawless and easy to use with unquestionable accuracy."

Pilots use GPS to continuously check flight accuracy and conditions for approach. They can automatically sequence up to 40 flight plans with 40 waypoints each, show the nearest airport, plan vertical descents, and display minimum safe altitudes.

It was this application of Trimble GPS to a tricky navigation problem that brought FAA approval. The University was granted non- precision approach approval, the second such approval to a hospital landing pad in the world.

But you don't need your head in the clouds to use GPS for navigation.

But GPS navigation doesn't end at the shore.

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