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Old 29-04-2019, 06:48   #1
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Desired course NMEA datagram (which datagrams are supported?)

I am using OpenCPN to plot actual (gyro true) vs Course Made Good however I would like to see the "desired course" from the autopilot computer - basically it is the desired true course that I could plot when tacking?

It is probably allready supported, however I can't find a listing of NMEA datagrams and what they do visually (my rudder angle does seems to be omitted which is fair enough)

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Laro
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Old 29-04-2019, 11:27   #2
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Re: Desired course NMEA datagram (which datagrams are supported?)

I do not pretend to understand what the value you would like to receive actually should be. What your AP computer does produce (if anything, usually the only thing that actually comes from it is the gyro compass heading) you can see in the NMEA debug window - OpenCPN will show you everything that it receives, regardless of whether it knows what the data actually mean.
Probably the most complete description of the existing NMEA 0183 sentences is available at NMEA Revealed
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Old 29-04-2019, 22:04   #3
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Re: Desired course NMEA datagram (which datagrams are supported?)

Let me invert the question.
Is there a NMEA datagram that results in a line showing the bearing to and ending at the next waypoint?
Any such dataframe I can create with reasonable ease.

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Old 29-04-2019, 23:28   #4
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Re: Desired course NMEA datagram (which datagrams are supported?)

Did you rad the NMEA0183 description at the link Nohal indicated?
Those waypoint related ones?

You can compare with the the list of implemented NMEA sentences from the manual.
https://opencpn.org/wiki/dokuwiki/do...0183_sentences


Further the NMEA converter and the Tactics plug-ins might be of interest for you.
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Old 30-04-2019, 00:15   #5
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Re: Desired course NMEA datagram (which datagrams are supported?)

I saw the link and have been through them, but they do not describe the "effect" in OpenCPN.

I have generated the GPBWC like this:
<GREEN>08:18:21 (TCP:172.29.114.139:2947) $GPBWC,061921,3322.6730,N,11819.1498,W,359.3,T,359 .3,M,001.3,N,005*2d<0x0D><0x0A>

I do not have a magnetic compas in the simulator, T and M are identical.

My desire is just to have an ideal (green / blue whatever) line to a waypoint
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Old 30-04-2019, 00:49   #6
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Re: Desired course NMEA datagram (which datagrams are supported?)

xxBWC is not implemented in OpenCPN.

Tactics_pi has a feature you might want to use - the temporary waypoint:
https://opencpn.org/wiki/dokuwiki/do...actics#tactics

Another option is the EBL feature from the OCPN_draw plug-in
https://opencpn.org/wiki/dokuwiki/do...aring_line_ebl
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Old 30-04-2019, 01:01   #7
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Re: Desired course NMEA datagram (which datagrams are supported?)

Laro88
What I can see BWC is not used anywhere in OCPN so the desired effect of that sentence is not implemented.

One "work around" for you would be to point the WP, right click and select "Navigate to hear" and you'll will get a nice line and a data window with info about the track. The line will disappear when the WP is reached.
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Old 30-04-2019, 01:21   #8
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Re: Desired course NMEA datagram (which datagrams are supported?)

Thanks Håkan.

Would it be of interest if a xxBWC handler is implemented? If so then I will take a look at the code and see if it is something I can squeeze in.

The "work around" is not feasible (althrough it works), I only have NMEA datagrams available for interaction with OpenCPN.

Do you by any chance have a list of waypoint related NMEA datagrams - if I can fake it by creating two waypoints and plot these then it might be good enough for me.
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Old 30-04-2019, 01:34   #9
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Re: Desired course NMEA datagram (which datagrams are supported?)

Quote:
Originally Posted by Laro88 View Post
Thanks Håkan.

Would it be of interest if a xxBWC handler is implemented? If so then I will take a look at the code and see if it is something I can squeeze in.
May you explain what should this feature be good for before sending a patch implementing it?
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Old 30-04-2019, 02:33   #10
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Re: Desired course NMEA datagram (which datagrams are supported?)

I would like a line indicating the next waypoint (basically a visualization of what the desired heading is - and if feasible a visualization of where the target is)

As said I only have NMEA data strings to generate the visualization.

If HSC is supported then I can try to generate this, but the BWR or BWC contains the distance.

My end goal is to get the blue line as seen below :-)

NMEA Revealed

Click image for larger version

Name:	OpenCPNnextwaypoint.jpg
Views:	28
Size:	164.4 KB
ID:	191119
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Old 30-04-2019, 02:58   #11
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Re: Desired course NMEA datagram (which datagrams are supported?)

Quote:
Originally Posted by Laro88 View Post
I would like a line indicating the next waypoint (basically a visualization of what the desired heading is - and if feasible a visualization of where the target is)

As said I only have NMEA data strings to generate the visualization.

If HSC is supported then I can try to generate this, but the BWR or BWC contains the distance.

My end goal is to get the blue line as seen below :-)

NMEA Revealed

Attachment 191119
And what should this be good for? Where you are heading is clear from the route you are following.
And what device does produce this information?
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Old 30-04-2019, 03:44   #12
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Re: Desired course NMEA datagram (which datagrams are supported?)

Hi nohal.

It visualizes the deviation from the desired course in real time & is generated from some autopilot software. The ideal / desired route changes depending on external conditions, so it is just a single point in the near future.
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Old 30-04-2019, 03:48   #13
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Re: Desired course NMEA datagram (which datagrams are supported?)

The EBL from the OCPN-Draw plug-in will draw this vector.
You will just need to "attach" it to the next WP manually.
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Old 30-04-2019, 03:49   #14
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Re: Desired course NMEA datagram (which datagrams are supported?)

Quote:
Originally Posted by Laro88 View Post
Hi nohal.

It visualizes the deviation from the desired course in real time & is generated from some autopilot software. The ideal / desired route changes depending on external conditions, so it is just a single point in the near future.
I'm still missing the point. What is it good for? What does happen based on this information? Yes, the ideal/desired route changes depending on external conditions, but what does the information you want to visualize tell about them?
I also have never seen an autopilot generating this sentence, but suppose you are creating one(?)
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Old 30-04-2019, 04:09   #15
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Re: Desired course NMEA datagram (which datagrams are supported?)

I just shows you what the ships autopilot / rudder engine / whatever is "not" doing properly. The visualization makes analysis simpler as it visualizes the "what should the nav computer do" vs. what is going on.

I would like to use OpenCPN to help some troubleshooting / visualization on what is happening on an older ship where the autopilot code is on some old french mil. grade eproms that are only uv-erasable at best - seeing is believing :-)
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