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Re: [gpsd-users] How to get DGPS fix with RTCM2 stream from Ntrip caster

From: Gary E. Miller
Subject: Re: [gpsd-users] How to get DGPS fix with RTCM2 stream from Ntrip caster?
Date: Fri, 15 Jun 2018 08:19:23 -0700

Yo Hoong!

On Fri, 15 Jun 2018 09:52:13 +0800
Hoong Fai Yee <address@hidden> wrote:

> I have a u-blox M8T GPS module that can get 3D fix with DGPS when the
> module is connected to my laptop running u-center and setup as a Ntrip
> client receiving correction stream (RTCM2) from a remote Ntrip caster.
> However, I'm not able to get DGPS fix on my Raspberry Pi running gpsd.

In the past that would have been an interesting setup.  But no longer.

SBAS satellties made RTCM2 obsolete.  The exact same correction
data that RTCM2 provides is now broadcast from the SBAS birds directly
to your GPS.

> I specified the gpsd arguments "ntrip://" and "dgpsip://" in the same
> line, both pointing to the same IP address.

That feeds the RTCM2 data to gpsd, but gpsd does not forward it to
the GPS.  No one cares to code that since the data is now redundant.

> Any ideas how I might get it to work?

Better idea, dont bother.

Two ways to improve your GPS fix from the default. 

One is to implement a base/rover scheme using RTK.  But that only
improves the relative accuracy between the base and rover.

The second is to post process the raw data from the GPS.  You can then
get absolute accuracy under a cm, but the GPS must be stationary and
you have to wait several hours before you can post process.

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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