Re: My GPS-receiver is too good 2

[Gary E. Miller]

Yo Håkan!

On Wed, 15 May 2024 20:53:50 +0200
Håkan Elmqvist <hakelm@smeden.org> wrote:

> Another interesting observation is that in the first position
> delivered by gpspipe the minute fraction is given with 5 decimal
> digits, all the following with four, se below:

Details matter.
What version gpsd?
What options to gpspipe?
What GNSS receiver?
Is your GNSS receiver set to NMEA, binary, or both?

> Any comment?

Not without details.

> As my old GPS-receiver died a quiet death I bought a cheap new one 
> labeled G-MOUSE.

G-MOUSE is generic.  You never know what you'll get.

> lsusb tells me it is a U-Blox AG [u-blox 7] which is confirmed by
> dmesg.

Ugh.  You can do a lot better for the price.

> Putting the receiver for 5 hours in my garden with a free sky
> and sending the output of gpspipe -r to a file and filtering the file

Better yet, grab 5 hours of JSON and/or raw.  Then you can make
scatter plots, sky maps, etc.

> I see that the indicated position all the time has stayed the same
> not changing a single digit

Then you are not looking at enough digits.

> even if the indicated speed all the time
> is 0.0724 knots.

Yeah, happens.

> My old receiver always wandered around a bit.

In its day, the 7-series was an improvement.  More so for the late
model 7's than the early ones.  But 4 digits not great these days.

> Has GNSS become so good and stable or is this some kind of software 
> cosmetics or most probably is there something I haven't understood?

The u-blox 7 can, optionally, have smoothing enabled.  And 4 digits
after the decimal place is only 11m resolution.  New $5 receivers
can hold 1m.

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

pgpON47dkzvTQ.pgp
Description: OpenPGP digital signature