NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Hundreds of millions of GPS receivers
From: Richard B. Langley
Date: 2009 Dec 18, 11:21 -0400
From: Richard B. Langley
Date: 2009 Dec 18, 11:21 -0400
Quoting anabasis75@aol.com:
> I can't agree with this Bruce. GPS isn't any more a single source than a
> celestial fix or a visual fix. GPS takes data from multiple birds and
> determines position from a minimum of two
A minimum of three is needed for a horizontal position if height is known or can be
assumed to be near 0 (sea surface). Why three? The receiver's clock offset from GPS
Time is generally unknown and changing second to second and therefore is estimated as
an unknown along with the receiver coordinates.
-- Richard Langley
, but usually four or more signals.
>
> As far as comparison, I'm interested in what kind of difference you are
> willing to accept between celestial and GPS position? Is a mile good enough,
> two, five? I just wonder what your standard is.
>
> Jeremy
>
>
> In a message dated 12/18/2009 1:25:45 A.M. Eastern Standard Time,
> brucerhamilton@gmail.com writes:
>
> I even think that a GPS has become an important part of celestial
> navigation. I call it my AP indicator. :-)
>
> Since GPS is a single source, I don't take it's data as true until I
> confirm it through something trustworthy like a celestial shot. I'm not sure if
> this GPS technology is always working, but the moon and stars are pretty
> reliable.
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===============================================================================
Richard B. Langley E-mail: lang@unb.ca
Geodetic Research Laboratory Web: http://www.unb.ca/GGE/
Dept. of Geodesy and Geomatics Engineering Phone: +1 506 453-5142
University of New Brunswick Fax: +1 506 453-4943
Fredericton, N.B., Canada E3B 5A3
Fredericton? Where's that? See: http://www.city.fredericton.nb.ca/
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