[time-nuts] Survey plot as art.

Gary E. Miller gem at rellim.com
Mon Jan 9 17:15:11 EST 2017

Yo Tom!

On Mon, 9 Jan 2017 14:01:18 -0800
"Tom Van Baak" <tvb at 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


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.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at 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
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