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All information gathered first-hand, since 1995

The GPS (Global Positioning by Satellites) system was implemented by the United States military to help them figure out where they are and to deliver their "hardware" accurately and efficiently. GPS is now used extensively in sports: mounted on motorcycles for desert ralleys; in racing sailboats, hand-held units for hikers, and competition gliding.

GNSS (Global Navigation Satellite System) is apparently a more complete navigation system based on the GPS technology. GNSS receivers and flight recorders (FR) are now used in gliding championships, with the position and height of the glider being recorded every 4 seconds.

Beyond reader Peter Sheppard of Auckland, New Zealand contributed the following account of the use of GPS in gliding.

Gliding contests usually last a couple of weeks and are made up of different tasks each day, seeking highest cumulative points. Tasks are usually races over several hundred kilometres around a series of predefined turn-points: triangle, polygon, twice out-and-return, etc. Gliders are individually timed from when they cross the start line to completion crossing the finishing line. Usually both lines are close to the flying base, e.g. St Auban. At the speeds and heights flown, it's essential to have an accurate method of verifying correct rounding of turn-points.

Until the last World Championships, here in N.Z., this was done by each glider carrying a pair of fix-mounted cameras. The glider had to enter a sector beyond each turn-point and photograph back to the turn marker (road-crossing, industrial chimney, or whatever specified) looking down the glider wing. Each evening the films had to be processed, angles assessed, etc to verify. Cloud could be in the way, film dodgey, etc.

With GPS, each glider carries a special GPS flight recorder. The GPS recorders themselves were developed by Dave Allen, Cambridge AeroInstruments, U.S. It was the special processing which we developed in N.Z. The GPS units interrogate the GPS satellites every four seconds. This provides a record of the glider position and height within three or four metres at four second intervals, also glider speed.

When the gliders returned from a task, we uploaded the data into a local net of ten or twelve PC's with processing software. From this we produced, almost instantly, exact records of the turn-point tracks, height profiles of the whole flight, aircraft speeds, etc. We then transferred this verified data to another series of PC's which calculated the scoring which changes relatively as each glider result is entered. From here, cables carried the results out to banks of large video screens for public and pilots. Thus, within a matter of minutes of gliders landing, their updating computed results would be on display.