[Xastir] GNGGA vs GPGGA support

Thu Apr 11 13:11:38 PDT 2019

Now that's interesting... We have gps.c:nmea_checksum() which does compute
the checksum. It's not used in the GPS decoding, but is used in
gps.c:create_garmin_waypoint()

It's likely that function could be repurposed to compute the GPS checksum
for the decoding as well, then compared against the checksum we received.

On Thu, Apr 11, 2019 at 1:06 PM Curt Mills <curt.we7u at gmail.com> wrote:

> To answer Jason's question about checksum, no I don't think we check it.
> We probably should.
>
> Also: APRS _can_ have increased resolution: Use APRS compressed mode. I
> used to do that a lot, and it gives you precision of about a 2' by 3'
> rectangle.
>
> On Thu, Apr 11, 2019 at 1:02 PM Tom Russo <russo at bogodyn.org> wrote:
>
>> I should point out that these updates only refer to handling of attached
>> location receivers, and do not add support for raw NMEA posits as Jason
>> had suggested.  It should not be super difficult to add that support, but
>> it isn't done yet.
>>
>> On Thu, Apr 11, 2019 at 01:58:30PM -0600, we recorded a bogon-computron
>> collision of the <russo at bogodyn.org> flavor, containing:
>> > GNSS, GLONASS, Beidou, and Gallileo support is no on the main branch of
>> > the Xastir repo, no fork needed.  Update your clone, and you should be
>> able
>> > to use Xastir with multi-constellation receivers now.  So far it has
>> only been
>> > tested with GPS and GNSS receivers, but it should work with all the
>> others.
>> >
>> > If you try it and it doesn't work, please open a bug report on GitHub,
>> and
>> > we'll run it to ground.
>> >
>> > On Wed, Apr 10, 2019 at 10:56:38PM -0600, we recorded a bogon-computron
>> collision of the <russo at bogodyn.org> flavor, containing:
>> > > Turns out that the GNGGA/GNRMC vs. GPGGA/GNGGA issue is the reason for
>> > > the newly opened issue #53 on github (
>> https://github.com/Xastir/Xastir/issues/53),
>> > > and I believe I have it fixed with pull request #58 (
>> https://github.com/Xastir/Xastir/pull/58)
>> > >
>> > > If any users with GLONASS receivers that emit GNGGA/GNRMC sentences
>> (such
>> > > as the DRAWS hat for Raspberry Pi) would like to test it out,
>> > > you can get it via:
>> > >
>> > >    cd <your clone>
>> > >    git checkout master
>> > >    git checkout -b tvrusso-feature-supportglonass master
>> > >    git pull https://github.com/tvrusso/Xastir.git
>> feature-supportglonass
>> > >
>> > > Then rebuild Xastir and try it out.
>> > >
>> > > The more folks I can get testing this the better.  I won't merge to
>> master
>> > > until I at least confirm that it helps the GN vs. GP thing.  As far
>> as I can
>> > > tell so far, I haven't borken it for GP.
>> > >
>> > > On Sun, Dec 02, 2018 at 02:52:06PM -0600, we recorded a
>> bogon-computron collision of the <kg4wsv at gmail.com> flavor, containing:
>> > > > I just started playing with a u-blox 8 family GPS.  It's capable of
>> > > > receiving multiple GNSS simultaneously. At first glance this unit
>> doubles
>> > > > the number of available satellites just because it's listening to
>> GLONASS
>> > > > and GPS at the same time.
>> > > >
>> > > > Of course there's a downside. In APRS-land we're used to dealing
>> with a
>> > > > single "talker ID" that indicates we're dealing with GPS (the name
>> of the
>> > > > US system) - that's the "GP" in GPGGA and GPRMC. This system uses
>> GN as the
>> > > > talker ID when it's listening to multiple systems.  I can configure
>> it to
>> > > > use GPS only and get my familiar GPGGA, but I stop listening to a
>> bunch of
>> > > > available satellites when I do that.
>> > > >
>> > > > Since APRS has limited resolution we (APRS users) wouldn't benefit
>> much
>> > > > from increased accuracy, but we would get something from having a
>> much
>> > > > larger constellation available.
>> > > >
>> > > > Has anyone messed with these multi-GNSS receivers? Are the benefits
>> that
>> > > > seem obvious at first glance real?
>> > > >
>> > > > Would it be appropriate to think about code changes to Xastir (or
>> other
>> > > > clients but i don't use those) to use G[PLABN]GGA or G[PLABN]RMC
>> instead of
>> > > > restricting ourselves to GP only? There would be 2 cases here, once
>> for the
>> > > > attached GPS interface to determine our position, and the GPGGA
>> APRS packet
>> > > > type.  I'm actually considering using GGA and RMC packets to get
>> increased
>> > > > resolution on a non-144.39 tracking application.
>> > > >
>> > > > Does xastir verify the NMEA checksum from an attached GPS?
>> > > >
>> > > > -Jason
>> > > > kg4wsv
>> > > > _______________________________________________
>> > > > Xastir mailing list
>> > > > Xastir at lists.xastir.org
>> > > > http://xastir.org/mailman/listinfo/xastir
>> > >
>> > > --
>> > > Tom Russo    KM5VY
>> > > Tijeras, NM
>> > >
>> > >  echo "prpv_a'rfg_cnf_har_cvcr" | sed -e 's/_/ /g' | tr [a-m][n-z]
>> [n-z][a-m]
>> >
>> > --
>> > Tom Russo    KM5VY
>> > Tijeras, NM
>> >
>> >  echo "prpv_a'rfg_cnf_har_cvcr" | sed -e 's/_/ /g' | tr [a-m][n-z]
>> [n-z][a-m]
>>
>> --
>> Tom Russo    KM5VY
>> Tijeras, NM
>>
>>  echo "prpv_a'rfg_cnf_har_cvcr" | sed -e 's/_/ /g' | tr [a-m][n-z]
>> [n-z][a-m]
>>
>> _______________________________________________
>> Xastir mailing list
>> Xastir at lists.xastir.org
>> http://xastir.org/mailman/listinfo/xastir
>>
>
>
> --
> Curt, WE7U        http://we7u.wetnet.net
> http://www.sarguydigital.com
>

-- 
Curt, WE7U        http://we7u.wetnet.net        http://www.sarguydigital.com