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@PaddyB, you didn't understand the question.
that's what it sounded like you asked, "is there courseOverGroundMagnetic?" Try asking differently maybe?
i don't understand your question any better than Paddy does
Heh. As knew, the NMEA0183 VTG sentence (and other) has no differences between 0 magnetic course and no magnetic course. But SignalK must have.
But I see that courseOverGroundMagnetic == 0 instead null when the VTG field three in all sentences == 0.
So yes, I asked, "is there courseOverGroundMagnetic?"
If the VTG field is empty then sk value is null. Zero in VTG converts to zero in SK
GitHub
nmea0183-signalk/hooks/VTG.js at master · SignalK/nmea0183-signalk
NMEA0183 to Signal K parser. Contribute to SignalK/nmea0183-signalk development by creating an account on GitHub.
A small part of GNSS receivers send empty if no magnetic course. Majority send 0.
Well, you'll have to make a crutch again, instead of just using SignalK.
What I if the heading really is zero?
Well, we can change things if it makes sense. Cog from gnss is probably extremely rarely exactly zero, so treating zero as invalid makes sense if that is how things mostly work
Are you talking about magnetic specifically? Or are you saying that if both magnetic and true are zero then the input is invalid?
Just I doing a display of courseOverGroundMagnetic in my new plugin 🙂
But yes, in NMEA0183 mostly no difference between 0 and no value (AIS has it). The gpsd somehow solves this problem, but no SignalK.
A naive approach can be suggested: if the value == 0 during of n seconds then the value = null. I'm going to implement it.