http://www.leapsecond.com/pages/gpsdo-sim/

    Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin

Yo Tom! On Mon, 9 Jan 2017 14:01:18 -0800 "Tom Van Baak" <tvb@LeapSecond.com> wrote: > Hi Gary, > > > Clearly the Adafruit is not high accuracy. I have played with some > > short baseline DGPS (cm level data) and not found any issue with > > antenn separation. > > I'm surprised by your claim. My measurements show that the Adafruit > is a wonderful GPS receiver. Yes, I also find the Adafruit wonderful. It was my favorite GPS when I got it. I just find that the Uputronics GPS HAT is even better, for the same price. Compare these two pages, the first the Adafruit, the second an Uputronics Version 2. Sitting right next to each other, both iwth matching GPS antennas.: https://pi2.rellim.com/day/ https://pi4.rellim.com/day/ Especially check out the scatter plots. The number of sats received, and the DOPs, are consistently better on the Uputronics. > Attached are ADEV MDEV TDEV plots of 5 > different GPS/1PPS receivers. The raw data is from: > > http://www.leapsecond.com/pages/gpsdo-sim/ What? No pretty graphs? :-) > The Adafruit "Ultimate GPS" (MTK3339 chipset) does very well. It's > also cheap, has a built-in antenna, has a uFL connector for optional > external antenna, runs in 3D so you can use it mobile or fixed, you > don't have to bother with survey or sawtooth correction. The data you > see above is out-of-the-box; you give it 5V and out comes a 1PPS: I find the Adafruit works better for me indoors with an external antenna. I find the uFL a pain for lab use. The Uputronics have no internal antenna and an SMA connector. Plus it has a u-Blox 8. But, to be fair, both are far beyond any practical needs I have. YMMV. RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 gem@rellim.com Tel:+1 541 382 8588 Veritas liberabit vos. -- Quid est veritas? "If you can’t measure it, you can’t improve it." - Lord Kelvin

Hi Gary, Your ADEV plots differ from mine by orders of magnitude. Remember this is time-nuts, not an NTP or a GPSD forum. The Adafruit GPS board is fine, even fantastic. But I suspect there are issues with your measurement techniques. I'm happy to help, but let's take this off-list. Thanks, /tvb

    Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin

Yo Tom! On Mon, 9 Jan 2017 16:37:27 -0800 "Tom Van Baak" <tvb@LeapSecond.com> wrote: > Your ADEV plots differ from mine by orders of magnitude. You are right, my ADEV plots are junk. Removed. It was the 24 hour scatter plots that I wanted you to look at. Hard to argue with lat/lon data as reported by the device. You can also checkout the TDOPs which are better on the MAX-M8N > Remember > this is time-nuts, not an NTP or a GPSD forum. The Adafruit GPS board > is fine, even fantastic. But I suspect there are issues with your > measurement techniques. Hard for me to accept your relative opinion of two devices when you have never played with one of them. Whatever my techniques may be, I have side-by-side concurrent data for many GPS. Hopefully any systematic errors cancel out in the comparisons. And anyone can run, maybe even improve, the FOSS programs I'm using for comparison as well. But I agree, moving off topic for time-nuts. RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 gem@rellim.com Tel:+1 541 382 8588 Veritas liberabit vos. -- Quid est veritas? "If you can’t measure it, you can’t improve it." - Lord Kelvin