I am new to this list and to this topic, but it seems to me that if one
wants to come up with an average of a set of spatial measurements, one
would use distance as the parameter to be averaged. The distance would
presumably be that from a fixed spatial reference point (0,0,0). One
would then take the square root of the sum of the squares of latitude,
longitude and height. My problem with this is that I can't see what one
would use for the reference point, but maybe that is not important (or
maybe it is!).
DaveD
On 12/15/2014 2:48 AM, Hal Murray wrote:
olep...@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
filtering.
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
case.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
