Re: [gpsd-dev] [PATCH] Fix on NMEA driver 2D mode

[Eric S. Raymond]

José Miguel Gonçalves <address@hidden>:
> The problem happens when only partial NMEA messages (but enough to
> supply a PVT) are sent by the receiver, and it's only solved when
> you use the test (session->newdata.mode != MODE_2D).

Under what circumstances can this happen? It doesn't seem to occur
with the full log.  Does it happen only when the sentence inventory
emitted is reduced?

I'm reluctant to change that test because doing that would break
functionality on other devices.  If that means we have to attach a
note saying you can't disable sentences and still expect the PolaR2x
to work with GPSD, then that's how it has to be.

> Meanwhile, another problem that I've detected is that, when the
> receiver supplies a GBS message, gpsd never uses it because of the
> time stamp test. In that case I always see the log message "second
> in $GPGBS error estimates doesn't match". I had to remove the
> timestamp test in processGPGBS(), to be able to use the GBS info. I
> prefer to have accurate error information supplied by the receiver,
> even if with a 1 second delay, that one that is extrapolated by gpsd
> using DOP values.

I agree, the reported error estimates are preferable.  This sounds like
the device may be hitting some kind of strange edge case in the NMEA
driver's cycle-detection logic.  Again, the fix here may well be not to
try to reduce the set of sentences omitted.
-- 
                <a href="http://www.catb.org/~esr/";>Eric S. Raymond</a>