unstable heading reading

[Hakan]

I should have started to see what's actually received from the compass unit.
Since it's serial connected to your SignalK use the Databrowser too see the data flow. There you can see e.g "navigation.HeadingMagnetic" or maybe "navigation.HeadingTrue". Compare my shot.
Look for different sources and the time stamp for last message. If any strange data or slow update rate you've to check your Furuno device settings.

The other way is to instead connect the compass serial port direct into OCPN and use the "NMEA Debug Window" to see what's coming in and the time rate. (You have to first disconnect it from SK. Only one at the time to a single serial/USB port!)
See shot 2 how to use a filter.


Remember OCPN will clear the heading data if more than six seconds between each message. That's the Watchdog.

[wefleenor]

Thanks, Hakan, I will be back to the boat next week.

[Tehani]

Originally Posted by wefleenor

I only recorded a very small time period, but the heading went in and out 3-4 times. Not knowledgeable enough to know the problem.


https://1drv.ms/u/s!AsqqtXq_ThqYhaIr...6hNOw?e=UyRxxE

Apparently in the log, the GPS is N2K and the COG-SOG rapid update and POSITION rapid update PGN's are jamming the heading information.

Can you configure the Maretron to reduce the rate of VTG and GLL sentences?

[stevead]

Quite a few of the recorded NMEA 183 sentences are going to be problematic.
For example

$IIGLL,4048.22985,N,12410.68037,W,,V,N*5A
$IIVTG,069.9,T,,M,0.04,N,0.07,K,N*10
$HCHDG,54.1,,,0.0,E*19

For the GLL sentence, the last two characters, "V,N" mean the data is Invalid (V) and FAA Mode Data Invalid (N).
Similarly the FAA mode indicator for the VTG sentence, also indicates Data Invalid.
But then there are valid Heading (HDG) sentences.
Not sure how you are feeding SignalK and what sentences your Furuno Compass emits, (I'm guessing the HCHDG sentence), but I think you need to clearly understand your data flows.

[Tehani]

You can set an input filter on OpenCPN, on the USB100 channel to remove some "garbage" generated by the GPS. Set it to only accept DPT sentences from the sounder, GGA, RMC and VTG, the rest are superfluous. Add RMB if the GPS is also a plotter.

[wefleenor]

Hakan,

I get no nmea output through the OPCPN nmea debug window and I get nothing. I aaume the heading sensor is no longer outputing data. Thanks.