Be careful when using one unit's location to set a different model's location... particularly the altitude. Some devices report altitude in MSL, others in AGL... and different units may use different models for the ellipsoid. You are always better off using coordinates generated by the particular device (either the built-in self survey or something like Lady Heather's precision survey). I did some tests while developing Lady Heather's precision survey code. I got pretty consistent lat/lon/alt results on the same units but consistent offsets between different models of receivers. I would suggest letting the Motorola re-surevy itself... it may have been a bit groggy after first being powered up after a few years of sleep... I know I am... --------------- > I then set the M12 reference location to the Lucent location as I know it to be correct.

It was off 7.5KM, that’s a little beyond groggy, no? More like a trip to Vegas. I’ll let it rerun the survey and see if it gets closer. > On Jun 4, 2017, at 9:50 PM, Mark Sims <holrum@hotmail.com> wrote: > > Be careful when using one unit's location to set a different model's location... particularly the altitude. Some devices report altitude in MSL, others in AGL... and different units may use different models for the ellipsoid. You are always better off using coordinates generated by the particular device (either the built-in self survey or something like Lady Heather's precision survey). > > I did some tests while developing Lady Heather's precision survey code. I got pretty consistent lat/lon/alt results on the same units but consistent offsets between different models of receivers. > > I would suggest letting the Motorola re-surevy itself... it may have been a bit groggy after first being powered up after a few years of sleep... I know I am... > > --------------- > >> I then set the M12 reference location to the Lucent location as I know it to be correct. > _______________________________________________ > 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.

I did not finish the sawtooth explanation. One of the units is designed such that the PPS is always on the raising edge of an internal 10MHz clock. If the 10MHz clock were perfect this means the maximum error is 1/2 cycle. The software in the GPS choose site best edge to minimize error. the jump you see it when it selects a different cycle and jumps The software tracks the error and outputs an estimate of the root on the serial channel. You can verify this by plotting the sawtooth correction vs.time and see that it lines up with your observation of the jump back to zero error. There might still be errors cause by other things, like improper self survey but the results you reported are exactly like what one would expect from a unit that uses an oscillator edge to trigger PPS. It other words what you see is a design feature not an error. On Mon, Jun 5, 2017 at 6:40 AM, Jerry Hancock <jerry@hanler.com> wrote: > It was off 7.5KM, that’s a little beyond groggy, no? More like a trip to > Vegas. > > I’ll let it rerun the survey and see if it gets closer. > > > On Jun 4, 2017, at 9:50 PM, Mark Sims <holrum@hotmail.com> wrote: > > > > Be careful when using one unit's location to set a different model's > location... particularly the altitude. Some devices report altitude in > MSL, others in AGL... and different units may use different models for the > ellipsoid. You are always better off using coordinates generated by the > particular device (either the built-in self survey or something like Lady > Heather's precision survey). > > > > I did some tests while developing Lady Heather's precision survey code. > I got pretty consistent lat/lon/alt results on the same units but > consistent offsets between different models of receivers. > > > > I would suggest letting the Motorola re-surevy itself... it may have > been a bit groggy after first being powered up after a few years of > sleep... I know I am... > > > > --------------- > > > >> I then set the M12 reference location to the Lucent location as I know > it to be correct. > > _______________________________________________ > > 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. > -- Chris Albertson Redondo Beach, California

Chris, I think you are onto something. Running Lady Heather on this unit I see a line under “receiver” with the term “SawT” and a parameter of 24ns. So if we combine this information with what you teach below, it’s starting to look like maybe the M12 unit is doing something different than the Lucent. I am watching it today and I see 5 PPS that vary from the lucent pulse (used as a trigger) each about +20ns until it resets. Mark Sims, can you comment on the SawT parameter, I assumed being reported by the M12 GPS, displayed on Lady Heather? Thanks > On Jun 5, 2017, at 10:15 AM, Chris Albertson <albertson.chris@gmail.com> wrote: > > I did not finish the sawtooth explanation. One of the units is designed > such that the PPS is always on the raising edge of an internal 10MHz clock. > If the 10MHz clock were perfect this means the maximum error is 1/2 > cycle. The software in the GPS choose site best edge to minimize error. > the jump you see it when it selects a different cycle and jumps The > software tracks the error and outputs an estimate of the root on the serial > channel. > > You can verify this by plotting the sawtooth correction vs.time and see > that it lines up with your observation of the jump back to zero error. > > There might still be errors cause by other things, like improper self > survey but the results you reported are exactly like what one would expect > from a unit that uses an oscillator edge to trigger PPS. It other words > what you see is a design feature not an error. > > On Mon, Jun 5, 2017 at 6:40 AM, Jerry Hancock <jerry@hanler.com> wrote: > >> It was off 7.5KM, that’s a little beyond groggy, no? More like a trip to >> Vegas. >> >> I’ll let it rerun the survey and see if it gets closer. >> >>> On Jun 4, 2017, at 9:50 PM, Mark Sims <holrum@hotmail.com> wrote: >>> >>> Be careful when using one unit's location to set a different model's >> location... particularly the altitude. Some devices report altitude in >> MSL, others in AGL... and different units may use different models for the >> ellipsoid. You are always better off using coordinates generated by the >> particular device (either the built-in self survey or something like Lady >> Heather's precision survey). >>> >>> I did some tests while developing Lady Heather's precision survey code. >> I got pretty consistent lat/lon/alt results on the same units but >> consistent offsets between different models of receivers. >>> >>> I would suggest letting the Motorola re-surevy itself... it may have >> been a bit groggy after first being powered up after a few years of >> sleep... I know I am... >>> >>> --------------- >>> >>>> I then set the M12 reference location to the Lucent location as I know >> it to be correct. >>> _______________________________________________ >>> 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. >> > > > > -- > > Chris Albertson > Redondo Beach, California > _______________________________________________ > 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.