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Old 17-12-2016, 18:05   #16
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Re: Windvane Autopilot

Raymarine units steer to wind by telling the AP what compass course to steer. It doesn't use waypoints as compass direction is simpler and more to the point. Also, I think the wind shift limit is 10 degrees. This warning is important for obvious reasons. When on AP less lookout is happening on most boats. The ability to set the wind shift alarm limit would be nice.
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Old 17-12-2016, 18:52   #17
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Re: Windvane Autopilot

I am sending out two sentences, APB and RMB. The APB sentence has the following
cross track error
direction to steer, L or R
cross track units
Arrival Circle entered
Perpendicular passed at waypoint
bearing origin to destination
Mag to True
Destination waypoint ID
Bearing present position to destination
Mag to True
Heading to steer to destination waypoint
Mag to True
So I have to provide 'text' of the destination. This can be anything but I use 'WVANE'.

The RMB sentence has the following
cross track error
direction to steer, L or R
To waypoint ID
From waypoint ID
Destination waypoint lat
N or S
Destination waypoint lon
E or W
Range to destination
Bearing to destination true
destination closing velocity in knots
arrival status
So I have to provide a destination virtual waypoint, i.e. the lat and lon of the destination. I set this to be 1nm away from the current location in the required direction. The To waypoint is 'WVANE' and the From waypoint is 'BOAT'. Hopefully this should work.

My autopilot only uses the APB sentence, but some only use the RMB sentence, hence I am creating both.

Once the concept has been proven then the addition of alarms and extra options will not be a problem. But there is no point building them if this does not work.
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Old 17-12-2016, 19:53   #18
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Re: Windvane Autopilot

If the boat has no wind vane or way to measure apparent wind angle, then I cant understand how you are setting things up to steer to wind. Picking some virtual waypoint is just steering to a point - has nothing to do with wind. And how does it compensate for a wind shift, on its own?
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Old 17-12-2016, 20:44   #19
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Re: Windvane Autopilot

The prerequisite for using this plugin is an wind direction instrument on the boat that is sending wind information to OCPN. If you can display the wind information in the Dashboard plugin then you can use the Windvane plugin. If you have no wind information this plugin will load, but it will not try to steer the boat as it will recognise that there is no wind information available.

The 'virtual' waypoint is truly virtual. It does not exist. It is used to be able to construct the RMB sentence that needs a lat and lon as a destination. If you are only using the APB sentence this does not use the concept, only apparent wind angle. The heading information is supplied to this plugin from OCPN. So it could come from the GPS giving the COG or it could come from the autopilot or heading sensor supplying HDT, HDM or HDG sentences.
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Old 19-12-2016, 12:20   #20
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Re: Windvane Autopilot

For the error message popups/notifications I think they should be done with the watchdog, thats what it is for after all. This would leave the WV much cleaner and it will only deal with sending the correct navigation information to the autopilot and responding to JSON messages regarding current wind angle and the heading current heading and the heading recorded when the WV was started. This would be a little like the OD and WD interactions.
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