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Re: [gpsd-users] gpsd with ntrip

From: Gary E. Miller
Subject: Re: [gpsd-users] gpsd with ntrip
Date: Thu, 24 Jan 2019 11:38:47 -0800

Yo Ralph!

On Thu, 24 Jan 2019 17:18:39 +0100
Ralph Nemitz <address@hidden> wrote:

> Sorry, I made a mistake concerning the GPS model.
> I had a look into the device at the gps chip where I red "GNS 1301".
> It uses MediaTek MT3333 GNSS chip which can process RTCM3.1 data.

Let us nail this down.  Please start gpsd, then send us the output of
        gpspipe -w -n 4

> I know that I'm far away from the ntrip server calculations points.

You said 400 km.  RTCM3 is only useful if the server is less than 10 km

> Is it possible that the GNS 1301 sees this and therefore is does'nt
> take into account the DGPS data from the ntrip server?

Dunno, GPS makers don't say much about their internal software.

But, they do say how to use RTCM with the chip.  From the MT3333

    "In general, UART0 is used for NMEA output and PMTK command input,
    while UART1 is RTCM input."

So, you do NOT sent the RTCM on the same port that gpsd uses to
communicate to the GPS.  You send the RTCM on the second serial port.

> I checked with a logic analyzer that at Pin 6 the data from ntrip
> server are present, but I don't think that the data were taken into
> account to output lat, lon or alt?

Which would confirm what the data sheet says: what you are doing will
not work.

> Do you have an idea what I should do?

Yup.  put the RTCM into the second serial port.  But then it will
not help as the ntrip server is too far away.

Pretty much the same advice I have been giving you all along.

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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