[time-nuts] OT - GPS and North
Magnus Danielson
magnus at rubidium.dyndns.org
Sun Nov 22 01:07:39 UTC 2009
Bob Camp wrote:
> Hi
>
> If you only have one antenna and one receiver, the answer is fairly simple. Swing it around you head on the end of a long string. Plot the position reading vs time. Correlate the readings to the phase of the rotation.
>
> It does indeed work (it's a doppler scanner ...). You could easily argue that it's not exactly a stationary situation any more.
>
> Making it work correctly would involve a lot of work figuring out just how much lag the receiver has. You might have to swing it at a 10 rpm rate ...
Putting it on a constantly rotating platform would work too. I actually
made a comment about moving the antenna as an alternative to the use of
multiple antennas. You can use the velocity vector in correlation with
the local rotation indication to transform the local reference frame to
that of the direction to north. Just swinging it around is pretty
useless unless you bring that in correlation to that local reference
frame. Also, you would like a fairly stable swingrate so that
correlation becomes easier. Also, having a higher rate receiver, such as
10 or 20 Hz would also be nice. The PPS is a suitable reference pulse to
correlate angle-measurements with that of the position given.
Cheers,
Magnus
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