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Re: Strangeness with speed

From: Gary E. Miller
Subject: Re: Strangeness with speed
Date: Tue, 15 Feb 2022 10:22:56 -0800

Yo Владимир!

On Tue, 15 Feb 2022 15:23:27 +0300
Владимир Калачихин <> wrote:

> 14.02.2022 23:41, Gary E. Miller пишет:
> >> What needs to gpsd for compute of speed?  
> > two Time and Position Pairs.  speed = (p2 - p2) / (t2 - t1)  
> If that were true then gpsd would return the speed by GGA sentences
> only.

You need to go back to basic physics is you do not thing that
   speed = (p2 - p2) / (t2 - t1)  

I did not specify how gpsd decides what to set speed to in the JSON.  It
varies a lot by input, Your input is garbage, so the output will be

> But I don't observe it. If I send to the gpsd only a GGA
> sentences (from real NMEA log, without changes) - gpsd doesn't
> return a speed.

gpsd needs the time change to determine new fixes.  And then to decide
what to output.  Your time does not change, so that confuses gpsd.
Garbage in, garbage ou.

Fix your input.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703  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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