Compass info ?

[hasse_A]

Hi!

Don't know if this has been talked about before.
In the manual it says that if you have an electronic compass delivering NMEA data the boat symbol will be oriented according to this.

In the manual HDT, HDM and HDG are mentioned.
I can see $HCHDG in the data stream.
This is referenced to magnetic north and is a standard NMEA message.
Should it not also be valid ?

My symbol points all around when at anchor or at the slip.
The dashboard display the magnetic heading just fine.

/Hasse

[tkeithlu]

What do you mean by an electronic compass? If you mean a fluxgate, it will orient when you are sitting still. If you mean a GPS used as a compass, it can only tell direction when you are moving, so at anchor your "heading" keeps switching around because you are basically reading noise from slight movements of the boat or just uncertainty in the GPS location.

[hasse_A]

Originally Posted by tkeithlu

What do you mean by an electronic compass?

It's a 10 Hz fluxgate compass.
I thought it was obvious since it gives out NMEA string $HCHDG.
I fully understand that the GPS needs to be moving to get a heading unless it's a "GPS Compass".

/Hasse

[Hakan]

Hasse
As you've noticed Dashboard and others use the HDG sentence.

/*
   ** HDG - Heading - Deviation & Variation
   **
   **        1   2   3 4   5 6
   **        |   |   | |   | |
   ** $--HDG,x.x,x.x,a,x.x,a*hh<CR><LF>
   **
   ** Field Number:
   **  1) Magnetic Sensor heading in degrees
   **  2) Magnetic Deviation, degrees
   **  3) Magnetic Deviation direction, E = Easterly, W = Westerly
   **  4) Magnetic Variation degrees
   **  5) Magnetic Variation direction, E = Easterly, W = Westerly
   **  6) Checksum
   */

If the variation fields are empty WMM_pi will calculate the variation instead. (That's the best solution since you're not addicted to a recent table in your compass.)

To use the heading for your boat's orientation you'll have to enter a length for the line at: Tools > Ships > Own ship > Heading predictor length (NMi)

Can you see the HDG sentence also in the NMEA debug window?
Håkan

[hasse_A]

Originally Posted by Hakan

Hasse
Can you see the HDG sentence also in the NMEA debug window?

No HDG.
I see $HCHDG which is what my compass throws out and what I expected OpenCPN to use.

/Hasse

[hasse_A]

Sorry I might have misunderstood.
HDG is part of my $HCHDG ?
If so, then I see it.

/Hasse

[hasse_A]

NMEA-strings.

[hasse_A]

Originally Posted by Hakan

Hasse
To use the heading for your boat's orientation you'll have to enter a length for the line at: Tools > Ships > Own ship > Heading predictor length (NMi)

The Heading predictor length is set to 1 NMi, but no stable heading or Heading predictor can be seen.

/Hasse

[hasse_A]

OK, problem solved.
I had to enable WMM_pi in the plugin menu.
Thanks Håkan.

/Hasse

[Hakan]

Hasse
I've tested your compass data as a VDR replay and it's feeding Dashboard, keeps my boat pointing at 34 degr and when GPS says I've a speed also is the heading prediction line there.
You say the boat's symbol is rotating at anchor, is that correct? Is it not only jumping around caused by a jumping GPS signal?
Strange, your heading signal would work fine and keep the boat pointing correct.
Håkan

[hasse_A]

Originally Posted by Hakan

Hasse
Strange, your heading signal would work fine and keep the boat pointing correct.
Håkan

Now everything works as it should and the way I expect it to do.

/Hasse

[hasse_A]

Now it looks like this.
/Hasse

[Hakan]

Ok -fine!
WMM_pi is the one o thrust. I've always used it so have no experiences when a true heading is missing. Nice info from you then.
Thanks Håkan