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

[Greg Troxel]

Florian Kiera <address@hidden> writes:

> 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.

I wonder if you are sure you mean RTCM3 vs 2, and if this is pseudorange
corrections, or carrier phase.  That's not really the point you are up
to, though.

> Its supposed to send correction data via the ntrip caster to the
> moving PC's M8P. The fixed station part works, however using the

Could you describe the fixed station more precisely, as this is likely
of interest to many?  I am unaware of gpsd having ntrip caster (server)
support.

Also, you say "PC", but surely you are not running Windows.  If you just
mean "computer", that's fine.


> 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?).

I have run gpsd with an M8 attach on USB, and an ntrip string to fetch
data from my state's reference network, and that seems to work.

You said "only puts", but you didn't explain why you believe that.
Please try to be about 5x more precise in what you are seeing, and the
information that leads you to conclusions.

> 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).

You said "worked", but you again did not say what you saw that made you
believe this.  If you can't get the data from the M8, how do you know it
is using the corrections?

> 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)? 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?

You may or may not need to configure the M8P to accept correction data.
str2str might be doing that for you.

gpsd has debugging mechanisms.  Study the man page and other docs and
enable debugging, and use all the available tools to get insight into
what's going on.  See gpspipe which can show the correction stream in
json.


[I'm sure you know this, but all followups should be on the list; I do
not respond to private mail asking for help when the messages should
have been on a list.]