[time-nuts] GPS position averaging
hmurray at megapathdsl.net
Mon Dec 15 04:48:58 EST 2014
olepr01 at gmail.com said:
> My question is twofold; 1) is this for some reason a bad idea? And 2) How do
> I average the numbers? I can not put my finger on it but it "feels wrong" to
> average lat, long and height independently.
It seems like an interesting idea to me.
It would be interesting to run a test: setup a pair of identical GPSDOs
running off the same antenna but using different locations and see if you can
see any difference in the PPS or 10 MHz output.
You can do a filtering pass to dump anything with fewer than 4 satellites.
The survey code has a mode where it says "bad geometry". I don't know the
fine print on how that works.
I can get my elevation off a topo map. I'm not sure how to translate that to
GPS coordinates. Something like that might be another opportunity for
The refclock part of ntpd filters a batch of samples by discarding outliers.
Time is only one dimension, so the recipe is pretty simple: sort, compute the
average, discard either the top or bottom, whichever is farther from the
average. I'm not sure how to do something similar in 2 or 3 dimensions.
It might be interesting to make histograms of HDOP and friends. (before and
after any filtering you can come up with?) That may cover the bad-geometry
These are my opinions. I hate spam.
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