Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 03-07-2016, 10:00   #1
Registered User

Join Date: Feb 2013
Location: Chaguaramas, Trinidad
Boat: Allegro 33
Posts: 259
Compass info ?

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
__________________

__________________
hasse_A is offline   Reply With Quote
Old 03-07-2016, 11:15   #2
Senior Cruiser

Cruisers Forum Supporter

Join Date: Feb 2012
Location: Carrabelle, Florida
Boat: Self-built 44' steel trawler
Posts: 873
Re: Compass info ?

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.
__________________

__________________
tkeithlu is offline   Reply With Quote
Old 03-07-2016, 11:44   #3
Registered User

Join Date: Feb 2013
Location: Chaguaramas, Trinidad
Boat: Allegro 33
Posts: 259
Re: Compass info ?

Quote:
Originally Posted by tkeithlu View Post
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
__________________
hasse_A is offline   Reply With Quote
Old 03-07-2016, 12:28   #4
Registered User

Join Date: Nov 2012
Location: Orust Sweden
Boat: Najad 34
Posts: 1,968
Re: Compass info ?

Hasse
As you've noticed Dashboard and others use the HDG sentence.
Code:
/*
   ** 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
__________________
Hakan is offline   Reply With Quote
Old 03-07-2016, 12:33   #5
Registered User

Join Date: Feb 2013
Location: Chaguaramas, Trinidad
Boat: Allegro 33
Posts: 259
Re: Compass info ?

Quote:
Originally Posted by Hakan View Post
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 is offline   Reply With Quote
Old 03-07-2016, 12:35   #6
Registered User

Join Date: Feb 2013
Location: Chaguaramas, Trinidad
Boat: Allegro 33
Posts: 259
Re: Compass info ?

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

/Hasse
__________________
hasse_A is offline   Reply With Quote
Old 03-07-2016, 12:40   #7
Registered User

Join Date: Feb 2013
Location: Chaguaramas, Trinidad
Boat: Allegro 33
Posts: 259
Re: Compass info ?

NMEA-strings.
Attached Thumbnails
Click image for larger version

Name:	NMEA.jpg
Views:	42
Size:	145.2 KB
ID:	127321  
__________________
hasse_A is offline   Reply With Quote
Old 03-07-2016, 13:01   #8
Registered User

Join Date: Feb 2013
Location: Chaguaramas, Trinidad
Boat: Allegro 33
Posts: 259
Re: Compass info ?

Quote:
Originally Posted by Hakan View Post
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 is offline   Reply With Quote
Old 03-07-2016, 13:05   #9
Registered User

Join Date: Feb 2013
Location: Chaguaramas, Trinidad
Boat: Allegro 33
Posts: 259
Re: Compass info ?

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

/Hasse
__________________
hasse_A is offline   Reply With Quote
Old 03-07-2016, 13:19   #10
Registered User

Join Date: Nov 2012
Location: Orust Sweden
Boat: Najad 34
Posts: 1,968
Re: Compass info ?

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
__________________
Hakan is offline   Reply With Quote
Old 03-07-2016, 13:23   #11
Registered User

Join Date: Feb 2013
Location: Chaguaramas, Trinidad
Boat: Allegro 33
Posts: 259
Re: Compass info ?

Quote:
Originally Posted by Hakan View Post
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 is offline   Reply With Quote
Old 03-07-2016, 13:33   #12
Registered User

Join Date: Feb 2013
Location: Chaguaramas, Trinidad
Boat: Allegro 33
Posts: 259
Re: Compass info ?

Now it looks like this.
/Hasse
Attached Thumbnails
Click image for larger version

Name:	Plot.jpg
Views:	68
Size:	361.0 KB
ID:	127324  
__________________
hasse_A is offline   Reply With Quote
Old 03-07-2016, 13:40   #13
Registered User

Join Date: Nov 2012
Location: Orust Sweden
Boat: Najad 34
Posts: 1,968
Re: Compass info ?

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
__________________

__________________
Hakan is offline   Reply With Quote
Reply

Tags
compass

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Simrad Rate Compass vs Fluxgate Compass Yeti Marine Electronics 5 06-10-2014 10:31
S hemisphere compass to N hemisphere compass blewett_john General Sailing Forum 7 07-11-2013 07:49
Oz Noob - Manitou 32 or Compass 28 Info? blu Meets & Greets 2 12-06-2009 17:34
Info on London, UK live aboard info capcook Liveaboard's Forum 3 29-08-2008 18:58
Compass Deviatrion-Compass Card Paul Bradbury General Sailing Forum 6 05-02-2006 15:34



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 16:42.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.