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Dire is a bit strong.  If Emerson's numbers are correct, DGPS gives you 33'
and raw gives you 50'.  For general aviation (no CAT II approaches) you need
1800' of visibility to be legal for an ILS to 5R at Indianapolis.  That
gives you at least 18 seconds in which to sight the "runway environment" and
it should take you less than 1/4 second to correct that 17' offset, assuming
your hand and the winds were that steady to begin with.  If your safety is
compromised by that magnitude of error, then you made a major mistake in
commiting yourself to land at that time and place.  Airports for GA are less
than 10 minutes apart east of the Mississippi River.
Not an airline pilot, just a FLIP driver.
Roger
Note:
  CAT II and CAT III approaches require intensive, recurrent, crew training
and EXPENSIVE equipment.
  FLIP -- Air Traffic Control term for "F------ Little Itinerant Plane"
(the official decode for the F is "Friendly")
================================================
Richard B. Emerson wrote
> DGPS accuracy won't increase with SA switched off, it will remain the
> same: 10 meters CEP for 95% probability (there's a 95% confidence you
> are within 10 meters of whatever the fix is).  Raw GPS without SA gives a
> 15 meter CEP.
----- Original Message -----
From: "Tony" <Severdia@XXX.XXX>
To: <NAVIGATION-L@XXX.XXX>
Sent: Tuesday, May 02, 2000 9:13 PM
Subject: Re: GPS Accuracy Now.
> Ed Falk wrote:
> >
> [snip]
>
> > I've been wondering the same thing.  There might still be a use for it
(DGPS)
> > in aviation.
>
> There is an absolutely dire need for it in aviation. Even for General
> Aviation (private) pilots. It matters for "life, liberty and the
> pursuit of happiness".  :)
>
> The whole prospect though appears to obsolete what the FAA and others have
> under development for commercial aviation, which aimed at a totally
> different system incorporating devalued GPS plus their own corrections.
> Any comments to add from the pros reading here?  (There were one or
> two airline pilots tuned in a few months ago).
>
> All in all, the events bring many changes for the future we can be sure.
>
> Tony    San Francisco
>
> ps: be sure to follow the notifications previously posted today.
>

   

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