Re: Wind

[Gary E. Miller]

Yo Владимир!

On Mon, 29 May 2023 20:35:24 +0300
Владимир Калачихин <v.kalachikhin@gmail.com> wrote:

> I tried to create NMEA flow generator with wind info. And I see a
> strange.

The NMEA/AIS world is strange.
 
> First:
> As it seems to me, min NMEA flow for this must contain RMC and MWV 
> sentences only.

Sounds more like a maximum, or ceiling, then a minimum.

Wind can also come from WMD instead of WMV.  If there is a wind message
that gpsd misses, then let us know.

> And it is so for SignalK.

What is SignalK?  Why do we care?

> But not for gpsd.

What is not for gpsd?

> In order for the gpsd return 'wspeedX', in NMEA must also be a DBT
> sentence. Am I missing something?

Needing depth to get wind speed would be a bug.  Can you provide a short
message sample that proves this?

> Second strange:
> The result of
> gpsdecode < shortWithWind.nmemea
> is different from
> gpsfake shortWithWind.nmea

Of course, they do different things.

> I do:
> in one terminal:
> gpsfake shortWithWind.nmea
> in other terminal:
> gpspipe -w
> I see a 'wangler' in json.
> 
> If I remove last string from shortWithWind.nmea and repeated - no a 
> 'wangler' field in json.

Oh.  Your sample is too short.  gpsd does not understand short test samples.
gpsd expectes a continuous data stream, and tries to combine consecutive
messages into fewer JSON messages.  But there were no more incoming messages
to help push out the stacked up messages.   Users/clients complain when
gpsd sends one message out for each message in.

Twy a 3 second message stream and things will work better.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        gem@rellim.com  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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