Hi > On Dec 15, 2014, at 7:19 PM, Bill Hawkins <b...@iaxs.net> wrote: > > This may be one of those cases where the human brain's ability to see > patterns would help to see the distribution and eliminate outliers. Plot > a manageable set of X and Y points, and another set of X and Z points.
yup > > To make the three dimensions plot as one in a statistical distribution > (bell) curve, use the magnitude of the vector. > > What do the surveyors instruments do that can get them down to a few > centimeters in half an hour? The ones around here use a survey grade GPS and log the data to a file. They do a bunch of post processing to get the solution to a desired level of accuracy. Last time I had it done, they had more fun looking at the GPSDO’s than running their fancy GPS. > > You might also want to study what's been said about the causes of > variance. The atmosphere is not uniform. Ionospheric issues are one of the things that gets corrected for to make a more accurate result. > > Consider the relative effect of position on time, where one foot or 30 > cm is equivalent to 10E-9 second. …. and some of the errors between solutions are > 10 feet. > > Also consider the 'averaging' period of the PLL filter in the > disciplined oscillator. The problem shows up when the GPS constellation is in a configuration that accentuates the error. That’s often a 12 / 24 / 48 hour sort of thing. Bob > > I'm no expert, especially not in math. These hints are thoughts that > come to mind. > > Bill Hawkins > > > -----Original Message----- > From: Ole Petter Ronningen > Sent: Monday, December 15, 2014 3:04 AM > > I would like to get a better idea of what my actualt antenna location > is, so that I can manually set the position in the GPSDOs. For that > purpose I set up a Ublox M8N with logging in U-center, and I've > collected about 250K readings over several days. For each reading I also > log number of SV's used, as well as HDOP, VDOP. PDOP, thinking I would > filter the list and end up with a subset of really good fixes.The idea > is then to average the "best readings" and use that as my position. > > 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. > > Any hints are greatly appreciated. > > > _______________________________________________ > 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. _______________________________________________ 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.