Re: [Question] gpsd, ntrip & C94-M8P (u-Blox)

[Gary E. Miller]

Yo Florian!

On Wed, 22 Apr 2020 12:08:02 +0200
Florian Kiera <address@hidden> wrote:

> Hello there, I got a question regarding to the use of correction data
> in gpsd.

Cool.

> Using latest Arch Linux (5.6.6) and the latest gpsd version (3.20).

Good, the last release.

> I am using a C94-M8P from u-blox to receive DGPS-information (RCTM3)
> and transfer it via ntrip to another PC that is connected to a 2nd
> M8P that is moving around.

A common configuration.

> Its supposed to send correction data via the ntrip caster to the
> moving PC's M8P.

Think of NTRIP the way you think of TCP.  Just one layer of many that
has to work for the project to work.  Only TCP is actually
documented...

> The fixed station part works,

How do you know that?

> however using the
> command: "gpsd -n /dev/ttyACM0 -G ntrip://:@IP:PORT/STREAM" only puts
> the information, the ntrip caster is giving out and the M8P is giving
> out, into the PC itself but not to the M8P (the USB port since it is
> not addressed at that point?).

Uh, missing a bunch of details.  Are you now talking about the rover
config?

> What worked for me was using RTKlib's
> str2str that uses an input stream (ntrip caster) and gives it to the
> output stream (the USB port of the M8P).

And you are not using the serial port?  The common configuration is
to have the base send data to the rover over a port on the roer that
gpsd is NOT using.

> But using this command won't
> allow me to access the exact data of the moving M8P because the port
> is already used to receive correction data. GPSD would be able to
> give the correction data from the ntrip caster to the M8P (atleast
> what the information of the manual tells me) and ALSO receive the
> corrected exact coordinates of the M8P (the 2nd M8P uses the RCTM3
> messages and its own coordinates to give out an accurate position in
> NMEA) and write them into the shared memory so I might be able to use
> them for my CUI.

You realize that is one really long run-on sentence?  I'm unclear how to
parse that.

> So my question is: Whats the correct use of gpsd to send and receive 
> correction data from different sources (receive from ntrip, send to 
> USB)?

This is UNIX, many ways to skin the cat.

The most common solution is to NOT send the base RTCM3 data to the rover
over the rover USB.  But instead to a rover serial port not used by gpsd.

> Do I need to change any settings of gpsd to tell it that M8P is 
> able to use the RCTM3 data or something like that?

Nope.  But there are a TON of setting in the M8P that need to be changed.

You made no mention of how you configured your base and rover and how
you verified that config.

Other people have done what you are trying, but it requires changing the
configuration  on the rover after you start the rover gpsd.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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    "If you can't measure it, you can't improve it." - Lord Kelvin

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