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Old 26-09-2013, 12:18   #46
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Re: NMEA 2000 quandry

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Originally Posted by rgleason View Post
This thread has worked its way through lots of terrritory: Autopilots, AP Equipment, Nmea2000, Nmea0183, Specific Nmea sentences, Magnetic, WMM , (a wobbly earth). The title should probably have "Autopilot" and "Magnetic" in it. ...watching this movie waiting for the outcome. Thanks to everyone who is contributing.

I hope there is working (but technically solid) Tracker Feature Request that comes out of this... Hakan has responded to Tugwit in a companion Autopilot thread
Yes, I did open FS#1151 - Add Option for APB to be output with Magnetic Bearings.

But you're right : the title should have "Autopilot" in it...

A much larger issue is potential support of NMEA 2000 in OCPN: the ability to read, decode, and accept input data from certain PGN (which several nav programs do now) and output relevant PGN such as 129283, 129284 for autopilot control and perhaps other PGN.

But that's a discussion, perhaps, for another thread....
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Old 26-09-2013, 13:14   #47
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Re: NMEA 2000 quandry

Thanks, Tugwit, now recall the Tracker task. ...Help me out please. What is PGN? (something like program navigator?) I've been trying to decipher it. Thanks
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Old 26-09-2013, 13:32   #48
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Re: NMEA 2000 quandry

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Thanks, Tugwit, now recall the Tracker task. ...Help me out please. What is PGN? (something like program navigator?) I've been trying to decipher it. Thanks
PGN = parameter group number
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Old 26-09-2013, 16:47   #49
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Re: NMEA 2000 quandry

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Thanks, Tugwit, now recall the Tracker task. ...Help me out please. What is PGN? (something like program navigator?) I've been trying to decipher it. Thanks
Yes, DotDun is exactly right. "Parameter Group Number" (e.g. 129284) is NMEA 2000-speak that is pretty much equivalent to "sentence" (e.g. APB) in NMEA 0183-speak.

Below, for example, are breakdowns of these two (as decoded by the Actisense EBL Reader). The PGN 129284 shown is, in fact, a translation of an APB sentence generated by OCPN. The translation was performed by my Actisense NGW (data conversion) gateway which output the PGN milliseconds after receiving the APB.

Typically, to output a PGN multiple 0183 sentences must contribute data and often vice versa is also true—there is no easy one-to-one correspondence. In this case, an RMB sentence (not shown) contributes the “origin waypoint number”, field 11 of the PGN.

APB (NMEA 0183 Sentence):
Basic Message
$ECAPB,A,A,0.000,L,N,V,V,358.498,T,Swanto,358.469, T,358.469,T*38

Full decoded Message
NMEA 0183 Sentence: EC APB (Heading/Track Controller (Autopilot) Sentence "B")
Number of Fields = 14
Original Length = 64
Description = Commonly used by autopilots, this sentence contains navigation receiver warning flag status, cross-trackerror, waypoint arrival status, initial bearing from origin waypoint to the destination, continuous bearing from present position to destination and recommended heading-to-steer to destination waypoint for the active navigation leg of the journey.
Field 2: Magnitude of Cross track Error, Nautical Miles = 0.000
Field 5: Arrival status = V
Field 6: Perpendicular passed at waypoint = V
Field 7: Bearing origin to destination, T = 358.498
Field 9: Destination waypoint ID = Swanto
Field 10: Bearing, Present position to destination = 358.469
Field 12: Heading-to-steer to destination waypoint = 358.469

129284 (NMEA 2000 PGN):
Basic Message
PGN: 129284 (0x1F904), SRC = 0, DST = 255, Priority = 3, Len = 34, Data = 10 A6 BA 00 00 C0 FF FF FF FF FF FF FF FF 65 F4 01 00 00 00 FF FF FF FF 1A B3 0C 1C B4 71 BF B6 00 00

Full decoded Message
NMEA 2000 PGN: 129284 (0x1F904)
Name: Navigation Data
Source = 0, Destination = 255
Priority = 3, Length = 34
Number Of Fields = 15
Field 1: SID = 16
Field 2: Distance to Destination Waypoint = 477.82 Metres
Field 3: Course/Bearing Ref. = 0 (Direction Reference True)
Field 4: Perpendicular Crossed = 0 (No,Off,Disabled,Reset,"0")
Field 5: Arrival Circle Entered = 0 (No,Off,Disabled,Reset,"0")
Field 6: Calculation Type = 3 (Null)
Field 7: ETA Time = Not Available
Field 8: ETA Date = Not Available
Field 9: Bearing, Origin To Destination Waypoint = Not Available
Field 10: Bearing, Position To Destination Waypoint = 6.2565 Radians (358.471 Degrees)
Field 11: Origin Waypoint Number = 1 NGW only transcribes purely numeric WPT numbers?
Field 12: Destination Waypoint Number = Not Available “swanto” is not numeric, therefore not converted?
Field 13: Destination Wpt Latitude = 47° 03.565980' N (47.0594330°)
Field 14: Destination Wpt Longitude = 122° 53.805000' W (-122.8967500°)
Field 15: Waypoint Closing Velocity = 0.00 Metre Per Second (0.00 Knots)
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Old 12-10-2013, 12:35   #50
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Re: NMEA 2000 quandry

Pleased to report that I successfully tested the option to output MAGnetic bearings in APB autopilot sentences. This feature is introduced in 3.3.1006 Beta.

With this option enabled, OCPN APB output permits my Simrad TP32 autopilot to successfully enter NAV mode and follow a route to the next waypoint.

Good work! Well done! Thank you!!
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Old 13-10-2013, 18:53   #51
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Re: NMEA 2000 quandry

+1 for NMEA2000 support.
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Old 13-10-2013, 20:28   #52
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Re: NMEA 2000 quandry

Were you guys looking at that canaboat project?
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Old 15-10-2013, 23:52   #53
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Re: NMEA 2000 quandry

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Were you guys looking at that canaboat project?
Hi Rick--
I'm aware of the CANboat project but am not that deep into deconstructing NMEA 2000 to make any practical use of its products or contribution to its efforts. (All in all, I think I'd rather go sailing )

I understand that Kees at Keversoft has contributed some useful technology (at least) to the project. He periodically contributes some useful columns to Panbo, as well.
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