Mike, Patrick, and M.F.Moon (commenters on GPS), Yesterday, there was a PBS segment on the development of GPS for Air Traffic Control. A prototype system is now being developed in Alaska. Alaska was chosen because bad weather and mountain obstacles are most hazardous there. Location of aircraft by GPS is proving to be accurate within meters! Location by radar remains good only within kilometers. Rates of crashes are already being reduced. Unfortunately, the cost of a system is about $10 000 to $20 000, even for small aircraft. Only larger commercial aircraft are presently included in the development testing.
Did you see the program? Gene Mechtly. ---- Original message ---- >Date: Wed, 21 Nov 2007 15:01:11 +0000 >From: "Michael Payne" <[EMAIL PROTECTED]> >Subject: [USMA:39736] Re: Altimeters >To: "U.S. Metric Association" <[email protected]> > >All aircraft currently use barometric altimeters, Although many aircraft now >have GPS as a navigation aid, they also have other backup methods of >navigation (Intertial Reference system and VHF Ground based navigation >aids). Until all aircraft have GPS, they will continue to use Barometric >altitude. There are many older aircraft in the US fleet, including many >major airlines that do not yet have GPS Navigation installed. In essense >what we are flying is a pressure. As long as every aircraft is on the same >altimeter setting of 1013 hPa were all on the same page. If we fly thru an >area of High pressure we'll be higher above the ground and flying thru a low >pressure area we will be closer to the ground. But all aircraft will be the >same altitude from each other and from the ground in the same area. > >Mike Payne
