[time-nuts] Re: Phase coherence with 2x GPSDO

[Bob kb8tq]

Hi


> On Mar 9, 2022, at 5:00 PM, Hal Murray <halmurray at sonic.net> wrote:
> 
> 
> kb8tq at n1k.org said:
>> If your drone is moving at 15 KPH, that???s a bit over 4 m/s. Roughly
>> speaking, you would need updates at > 10 per second to keep  this from
>> dominating the result. This would be true of both survey  and direct time of
>> flight measurements.  
> 
> Do I really need that update rate?  If the velocity changes slowly, both 
> magnitude and direction, then I can extrapolate.

It very much depends on how fast the drone is going and how far you need
to push the location error down in the “mix”. It’s not the only source of error.
Without any “smoothing” you get an update rate at 4 / 0.15 = 26 samples a 
second to be at the stated limit. If you need to push it down to a tenth of 
the combined total, then the straight up number would be 260 samples
a second. 

Is this drone targeting something? If so, 15 KPH would be quite slow. Speed
is very much application dependent. Like a lot of these things, we know 
very little about the details of the system. Thus all we can do is make random
guesses about key parameters. 

Bob

> 
> With access to the drone control signals, I could do a better job of 
> predicting the path.
> 
> The subject is GPSDO so I doubt if you want to be jerking the control voltage 
> around.  Is there any way to take advantage of that?
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
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