Re: Strangeness with speed

[Florian Kiera]

Am 17.02.22 um 15:20 schrieb Владимир Калачихин:

> 17.02.2022 14:14, Florian Kiera пишет:
> > Besides, its interesting that gpsd is calculating any speed at all 
> > with the "sentences.nmea" file you gave us, as multiple NMEA 
> > sentences are from the exact same time.
>
> I think that gpsd never calculates the speed and ignores any time.

gpsd does calculate the speed by using the latest TPV and the current 
TPV just fine. It uses simple mathematics so thats fine. As mentioned in 
my last email: speed is 0 because the TPV before that has the same 
coordinates so you haven't moved in that time at all.

> But may be everything previously said are empty words.
>
> In attachment - two NMEA files and two JSON outputs.
> The JSON is obtained from NMEA by
> cat sentences1.nmea | gpsdecode > senteces1.gpsd
>
> File senteces1.gpsd has speed == 0, file senteces2.gpsd - not.
> I don't see any differences between sentences1.nmea and 
> sentences2.nmea, except time. Both were created from one real NMEA, 
> but sentences1.nmea with changed time.
>
> If this is about time - what's wrong with times in senteces1.gpsd?
What actually wonders me is why does gpsd give out a different TPV with 
a small time difference? Maybe the high frequency of NMEA messages in 
sentences1 is at fault?

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