On Wed, Apr 25, 2018 at 7:56 AM, Tom Van Baak <t...@leapsecond.com> wrote: > List -- I had a recent query by a researcher who would like to pinpoint the > location of his telescope(s) within 0.3 meters. Also (he must be a true > scientist) he wants to do this on-the-cheap. He may have timing requirements > as well, but that's another posting. > > So I toss the GPS question to the group. Surely some of you have crossed the > line from precise time to precise location? > > How easy, how cheap, how possible is it to obtain 0.3 m accuracy in 3D > position? > > When we run our GPSDO in survey mode how accurate a position do we get after > an hour, or even 24 or 48 hours? And here I mean accurate, not stable. Have > any of you compared that self-reported, self-survey result against an > independently measured professional result or known benchmark? > > Do you know if cheap ublox 5/6/7/8 series receivers are capable of 1 foot > accuracy given enough time? > > If not, what improvement would -T models and RINEX-based web-service > post-processing provide? > > It that's still not close enough to 0.3 m, is one then forced to use more > expensive multi-frequency (L1/L2) or multi-band (GPS, GLONASS, Galileo) to > achieve this level of precision? If so, how cheaply can one do this? Or is > the learning curve more expensive than just hiring an survey specialist to > make a one-time cm-level measurement for you? > > Something tells me 1 foot accuracy in position is possible and actually > easier than 1 ns accuracy in time. I'm hoping some of you can help recommend > solution(s) to the researcher's question or shed light on this interesting > challenge.
Hi Tom, list, as another researcher who is also interested in telescope positions (!) I have done this for personal use at home with a ublox 6T and 53532A antenna to see what I got. I was logging in the UBX binary format with the raw (carrier phase) measurements turned on and then converting it to RINEX and using the NRC's CSRS-PPP online service which is one of the few that will take single frequency L1 only data. The results based on approx. 41.5 hours of data and which were post-processed 21 days later (so that they used the IGS Final products rather than the Rapids or Ultra Rapids) were Sigmas(95%) of 0.105 m, 0.089 m, 0.217 m in latitude, longitude and ellipsoidal height respectively. I was quite impressed with the results without use of the L2 frequency to correct for the ionosphere etc. > > Thanks, > /tvb > Cheers, Tim _______________________________________________ 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.
