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Re: [gpsd-users] Coding Question

From: Gary E. Miller
Subject: Re: [gpsd-users] Coding Question
Date: Tue, 5 Feb 2019 11:20:49 -0800

Yo Roland!

On Tue, 5 Feb 2019 10:28:32 -0800
Roland Oswald <address@hidden> wrote:

> So maybe I need to explain a bit more.


> I am receiving RTCM on a different device.

Yes, but the issue is where is that RTCM orginally from?

>  I need to forward those
> RTCM messages to the u-blox and then get the corrected gps.

Yes.  Easy, Just send that data in the second serial port of the u-blox.

> I did this with trimble, I just needed to forward the RTCM messages
> to the usb port, then on another usb port read the corrected gps.

Yes.  u-blox is the same.  gpsd read the 'corrected' data from the
primary port.  You shove the RTCM in the secondary port.

> The problem with u-blox, in this case, is that when I read for the
> corrected gps, there is a bunch of other stuff that is, I guess,
> u-blox formatting info.

Good.  Not a problem.  gpsd handles that stuff fine.

> I think that I need to configure the u-blox to accept the RTCM
> messages, with the ubxtool, first.

Maybe, I'm not sure about the defaults.  Trraditionally people
use u-center to program the u-blox, then save the config.  To avoid the
Windows u-center, some hand code a config tool.  Now comes ubxtool
which is new to the job, but flexible.

>  Then start sending the RTCM
> messages, which I was told should be the same as with the trimble.

No need for the 'Then'.  Just send the data.

> Then, finally, get the corrected gps without all the garbage stuff.

Yup.  Easy, normal, common.

> I think all I need help with is how to configure the u-blox with
> ubxtool,

That will take some back and forth as that has not been done before.
Prolly not too hard.

I do not have a pair of NEO-M8P, so I can't test on my end.  I do
have other u-blox that are close, but not what you are doing.

> and how to read the gps (just latitude and longitude) in
> either python code or c++ code.

No need for the RTCM to do that.  Just start gpsd: "gpsd -n /dev/ttyS0".
The "gpspipe -w" to see the JSON.

Then you get smarter from there.  The gpsd has many sample clients in
many languages.  Just look at them and see which look easy to you.

> I hope this doesn't come off as aggressive or like a jerk,

Nah, typical newbie stuff.  You are getting started and kinda lost.
Normal.  We try to help.

> I just
> don't want to be spending too much time on something that I might not
> need.

Well, we have no idea what you need.  We just know what is possible.

If you need lane level guidance that will be almost impossible with the
M8P without a very close base station.

You need to study the u-blox doc:


Specifically section 32.2

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  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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