[time-nuts] 1PPS accuracy of commercial GPS receivers

Poul-Henning Kamp phk at phk.freebsd.dk
Thu May 14 10:48:33 UTC 2009


In message <E660D55B75514E29A5735AF7DCB484B2 at athlon>, "Ulrich Bangert" writes:

>The receiver can use this redundant information in two ways:
>a) to improve the solutions for the position
>or 
>b) to improve the solutions for the time
>
>but not both at the same time. 

That's just bogus.

First of all, you need four sats for a complete solution: X+Y+Z+T, second
the more sats you add after that, provided they do contribute gainfully,
will improve both the position and time solutions, for the very simple
reasons that they are one and the same solution.

Once you go to position-hold mode, all the sats contribute to is the
time solution, and in principle one sat is enough to get a solution,
because, as the name implies, you stop treating X+Y+Z as variables.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.



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