NMEA 2000 quandry

[Tugwit]

I can't speak for the Triton, but I have a Raymarine ST70 on my N2K network and it displays BTW and DTW just fine when an OpenCPN route is active.

In my current configuration, OpenCPN only transmits ECRMB and ECAPB. These are picked up by my Actisense NGW-1-ISO and translated to PGN 129283-XTE and 129284-Nav Data which I can view and parse on the N2K network using an Actisense NGT.

It appears that only PGN 129284 is needed for BTW and DTW display on the ST70--unfortunately, Raymarine documentation is pretty thin on N2K specifics, to put it generously.

Can't speak to XTE display on the ST70. Will investigate.

[colemj]

Originally Posted by Down2TheC

If you're saying you can make a waypoint in OpenCPN and your T41 shows the name, bearing, and range of that waypoint... then you're one up on me. (And perhaps ActiSense.)

Again, I have the NGW-1-ISO, although I can't imagine that makes a difference.

I know the Simrad AP works just fine off of it using OpenCPN.

I know the Tritons work fine using Coastal Explorer, although I have never noticed the waypoint name (I usually do not name them in a route).

But I cannot say with certainty that I have used OpenCPN and looked at the Triton data page. I will try to do so.

Mark

[DotDun]

Originally Posted by Down2TheC

Of course I read the manuals and looked at the conversions, XTE works fine (129283) and 129284 has some, but BTW, RTW, etc isn't in the APB translation. The T41 can display that info when it's finding it.

They say they're working on it. Waypoint data won't display on the T41 with the conversions they have at present.

From ActiSense:
"We do intend to add waypoint conversions, but this is not a simple task.
The differences between NMEA 0183 and NMEA 2000 regarding waypoints is significant.
We cannot simply link between the two, it needs some serious consideration to ensure correct operation.
This has unfortunately delayed our implementation of this feature."

After a season without it, I've just wiped that page from the T41's and will live with waypoint info only being on the one 0183 display for the autohelm.

Hmm, the attached is from a saved N2K capture of the OCPN thru a NGW-1. Note field 2 & 10.

I never actually got my RM X-10 to accept it, but my conclusion is/was the RM wants btw in magnetic, not true. I say this as my Furuno MFD puts out an identical pgn on N2K with magnetic and the RM accepts it. Unless there is actually something wrong with this pgn and the Actisense NMEAReader/EBL software is masking the bad data (unlikely).

[Tugwit]

Originally Posted by colemj

Again, I have the NGW-1-ISO, although I can't imagine that makes a difference.

I know the Simrad AP works just fine off of it using OpenCPN.

I know the Tritons work fine using Coastal Explorer, although I have never noticed the waypoint name (I usually do not name them in a route).

But I cannot say with certainty that I have used OpenCPN and looked at the Triton data page. I will try to do so.

Mark

Mark, exactly what Simrad AP model are you using? I am unable to get my Simrad TP32 to enter NAV mode using OCPN, while it works fine with PolarView/PolarCOM. The only difference in the APB output of the two software products is that PolarCOM outputs bearings in MAGnetic while OCPN outputs bearings in TRUE.

In my configuration, both products are only producing ECAPB and ECRMB. Data supplied by RMC, if needed, is coming to the TP from an N2K/SimNet PGN.

As a result, I tend to agree with DotDun's conclusion--the APB supplied to some pilots (RM X10 in his case, TP32 in mine) is expected to be in Magnetic.

[colemj]

It is a Simrad AC42 and accepts both magnetic and true data.

I just looked in our NGW-1-ISO manual, and it states it converts both magnetic and true sentences.

One thing to note is the firmware you have installed in your NGW-1. Actisense has a special "AIS" firmware that drops a lot of the 0183 conversions in their normal firmware in favor of providing additional AIS data conversion. You may want to check on that.

Mark

[DotDun]

Originally Posted by colemj

I just looked in our NGW-1-ISO manual, and it states it converts both magnetic and true sentences.

Unfortunately, OCPN only puts out btw in true...

[colemj]

Originally Posted by DotDun

Unfortunately, OCPN only puts out btw in true...

Yes, and our NGW-1 converts that to the appropriate PGN, which our Simrad AC42 accepts.

But I will try to confirm this later - things are disconnected right now.

Mark

[colemj]

OK, I couldn't wait and reconnected enough of the system to test.

Turns out I am wrong on this - the AP does not get sufficient navigation info from OpenCPN via the NGW-1 to operate in Nav mode (gives a "Nav data missing" error).

It also does not operate when using a Maretron USB interface.

The Tritons show all the nav data just fine when OpenCPN is navigating a route - BTW, XTE, ETA, etc, so the information is on the network - just the AP is not using it for some reason.

I distinctly remember using OpenCPN with the AP, but maybe I am confused or have not set something up correctly here. I mostly use OpenCPN for planning and general charting on my Mac, and Coastal Explorer for running the nav stuff on a PC. I don't think I have ever used OpenCPN for navigating, but do remember testing it.

The Simrad AP works fine when using Coastal Explorer.

Mark

[DotDun]

Originally Posted by colemj

OK, I couldn't wait and reconnected enough of the system to test.

Turns out I am wrong on this - the AP does not get sufficient navigation info from OpenCPN via the NGW-1 to operate in Nav mode (gives a "Nav data missing" error).

It also does not operate when using a Maretron USB interface.

The Tritons show all the nav data just fine when OpenCPN is navigating a route - BTW, XTE, ETA, etc, so the information is on the network - just the AP is not using it for some reason.

I distinctly remember using OpenCPN with the AP, but maybe I am confused or have not set something up correctly here. I mostly use OpenCPN for planning and general charting on my Mac, and Coastal Explorer for running the nav stuff on a PC. I don't think I have ever used OpenCPN for navigating, but do remember testing it.

The Simrad AP works fine when using Coastal Explorer.

Mark

So the AP accepts Coastal Explorer running thru the NGW-1?

[colemj]

Yes, no problem - it always has and we have been using it for 2 years.

I'm thinking maybe I didn't set up something correctly on OpenCPN. The Tritons show all of the nav data when OCPN has an active waypoint, and the Simrad AP recognizes the OCPN/NGW-1 interface as a valid Navigation source. But I get a "no nav data" error on the AP when switching to nav mode. Same with the Maretron interface.

Mark

[DotDun]

Originally Posted by colemj

Yes, no problem - it always has and we have been using it for 2 years.

I'm thinking maybe I didn't set up something correctly on OpenCPN. The Tritons show all of the nav data when OCPN has an active waypoint, and the Simrad AP recognizes the OCPN/NGW-1 interface as a valid Navigation source. But I get a "no nav data" error on the AP when switching to nav mode. Same with the Maretron interface.

Mark

So, the only question that remains wrt the NGW-1, do you know if Coastal Explorer is send APB or RMB for navigation? I know OCPN sends APB. It's possible the NGW-1 handles RMB correctly but APB is broken (even though it looks good on NMEAReader).

Thanks for checking!!

[colemj]

Looking at the output sentence choices in the connection tool for OpenCPN 3.2.2, I see RMB and APB.

Coastal Explorer sends both RMB and APB.

Mark

[DotDun]

Originally Posted by colemj

Looking at the output sentence choices in the connection tool for OpenCPN 3.2.2, I see RMB and APB.

Coastal Explorer sends both RMB and APB.

Mark

I'm probably a couple versions back on OCPN. I'll have to dust it off and play with it.

Regardless, I'm still thinking the RM X-10 will only accept magnetic.

[Tugwit]

Originally Posted by DotDun

I'm probably a couple versions back on OCPN. I'll have to dust it off and play with it.

Regardless, I'm still thinking the RM X-10 will only accept magnetic.

I appreciate your contributions to this thread…nice to know others are having some issues getting OCPN talking to their Autopilot J

Question (for both you and Mark): how is your AP getting the data that originates with OpenCPN: NMEA 2000 or NMEA 0183 (or both)? Since OCPN only outputs 0183 data (e.g. APB, RMB), if an AP is connected solely via NMEA 2000, the AP must rely on the up-converted PGN (129283--XTE, 129284—Nav Data) through some sort of gateway, e.g. Actisense NGW-1.

In my case, I originally connected my AP (Simrad TP32) only via NMEA 2000 (SimNet). Using OpenCPN, I couldn’t get it to enter “Nav mode”, i.e. follow a route. Since the TP32 also supports NMEA0183 input, I wired it to the 0183 side of my data network and fed it the APB and RMB directly. I still couldn’t get it to follow an OCPN route. However, using PolarView/PolarCOM (which outputs the same sentences but with Magnetic Bearings) the AP does work!

I confess I haven’t (yet) tried using PolarView via NMEA 2000 only (i.e. disconnecting the 0183 inputs). I’ll do that soon and report. However, I have a couple observations that might help others:

I rely heavily on the Actisense NMEA Reader and EBL Reader to monitor the comings and goings of data on my network. Turns out, these products have a couple of errors in decoding APB:

1. When a NMEA 0183 APB Sentence contains MAGnetic bearings:
a. NMEA Reader APB Decoding is OK (shows BOD bearing as MAG), but
b. EBL Reader APB Decoding is in ERROR—shows (BOD) bearing as TRUE;
2. When a NMEA 0183 APB Sentence contains TRUE bearings:
a. NMEA Reader APB Decoding is in ERROR—shows (BOD) bearing as MAGnetic, but
b. EBL Reader APB Decoding is OK (shows BOD bearing as TRUE);
3. In both NMEA Reader and EBL Reader Decoding:
a. Field numbers in Decoding are off by 1, and
b. Final two bearing fields do not display as either True or Magnetic even though there are {M,T} codes in the Data (Bearing, Present Position to Destination, Heading to Steer).

You might double check the actual “data” when you use on the Actisense decodings…. (I did report this problem to Actisense).

Also, I just analyzed the NGW N2K conversions of the APB and RMB sentences output by OCPN and PolarView. OCPN just outputs true bearings in APB, so each APB/RMB pair seem to generate a corresponding 129283--XTE, 129284—Nav Data PGN pair.

PolarCOM, however, outputs its APB with all Magnetic Bearings. As a result, for each APB/RMB pair, the NGW produces three PGN on the N2K side: one 129283—XTE and two 129284—Nav Data PGNs.

The first of the 129284 PGN sets Field 3: Course/Bearing Ref to TRUE, field 9: (BOD) to “not available”, and field 10: (Bearing Pos to Dest) to a valid True bearing.

The second of the 129284 PGN sets Field 3: Course/Bearing Ref to MAGnetic, field 9: (BOD) to a valid magnetic bearing, and field 10: (Bearing Pos to Dest) to a valid magnetic bearing (equivalent to the True bearing output in the first PGN).

As a result, I’m optimistic that PolarView/PolarCOM might actually work with the AP in N2K-only mode since the PGN generated supply the magnetic bearings that the AP evidently requires.

If that turns out to be the case, folks wishing to use (some) autopilots with OCPN may wish to encourage OCPN development to permit the option of outputting APB with Magnetic bearings…. (see thread, Please Help: Magnetic Course Display in OCPN, http://www.cruisersforum.com/forums/f134/please-help-magnetic-course-display-in-opencpn-110952.html )

[rgleason]

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