Boat Icon Rotates 16 every 30 seconds

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I have a peculiar problem that started happening about 2 months ago on my NavNet 3D system. The boat Icon, rotates 16 degrees counterclockwise every 30 seconds exactly, for about 1 second, then flips back to the correct orientation. The 16 degrees corresponds to the magnetic variation here in Seattle.

The radar display also rotates at the same time because it is set for Heading up.

My guess is that the Navnet3d system is somehow recalculating the magnetic variation every 30 seconds but displays one instant with a value of zero. If have looked the the magnetic variation value coming from the GPS200 Maretron receiver on the NMEA2000 bus and it is consistantly putting out 16.xx degrees. The heading sensor is an RC42 Simrad rate compass, also on NMEA2000 and it is consistantly putting out the same heading value since I am sitting at the dock.

If I configure the GPS200 not to output the magnetic variation, and reboot the NN3D system it will eventually get to right heading and not flip 16 degrees every 30 seconds, but it seems to take an extra 5 minutes to figure out the magnetic variation ( by some other means I guess), and get the boat icon pointed the right way.

A possibly related by other problem, is that my GP320B Furuno GPS takes a full 15minutes to acquire the GPS signal - or at least the NN3D system takes 15 minutes to show current location coordinates when the GPS source is set to the GP320B. This just started happening, but isn't entirely reproducible - usually happens.

If I set the GPS source to the Maretron GPS200 in the installation wizard the system boots up and immediately has a location fix. If I set the GPS source to the FA50 then it takes 10 minutes to get a GPS fix on reboot of the NN3D. But the Maretron gets the GPS in less than a minute when it boots.

I am stumped by both of the these problems and would welcome any and all insights.

My guess is you are having some NMEA2000 networking issues. I would recommend first ensuring you are running the current NN3D software (2.07). Next I would disconnect items from your backbone like the Maretron and start with a very limited backbone of items. I am concerned about your GP330B. It sounds like it isn't working at all. When setup as your primary source it should be providing you position but it appears to be auto switching to use another source of data on the network. (Hence the 15 mins, as the system seeks out another source of data to use) If you remove the other sources of position from the system and give it no choice to use the GP330B, I think you will find it isn't working. It could be that your NMEA 2000 network has issues or the GP330B itself does. It might require a dealer to get on the boat. As far as the pointing of the boat, when you have heading data (like from your Simrad) the icon uses heading (by default) NOT COG to point the boat. Check under your ship and track ICON and see that the boat pointing is set to heading. If the heading is still spinning the boat, then again it sound like a NMEA 2000 networking problem or someone has check marked heading where heading isn’t wired and lastly that someone has a secondary source of heading connected that doesn't meet the 100ms update requirements.
Johnny Electron,
I should mention that the GPS is a GP320B not the 330, which I guess plugs directly into the 0183 port on the back of the MFDBB. It is possible that the gps has failed and the long delay is the fail over timing. That doesn't explain why the FA50 takes 10 minutes to find the gps when it is set as the source though since it couldn't have failed too.

The boat icon is set to use heading, not cog - I have checked that a number of times. The heading data is updated every 5ms on the NMEA 2000 bus. I checked that yesterday with the Actisense data logger. Maybe every 5ms is too fast, although I don't know how to change that.

I hope to have someone on the boat this week to sort this out.

I appreciate your reply - I had hoped this might be something simple but as you say it could be some kind of NMEA bus issue that will take more investigation to find. I'll keep you posted.

How the system deals with resources varies by the software version you are running.
PLEASE confirm you are running the 2.07 software.
Sorry for the delay, I was out of town for a week. Yes, the system is running 2.07.

I had a knowledgeable dealer on the boat last week, and of course due to Murphy's law everything worked fine. The dealer ran the N2kAnalyser from Maretron to analyse instance numbers and found a few conflicting values. He fixed that and was satisfied that everything was setup correctly.

I was on the boat a couple of days later and the problem recurred exactly as it had before. The gps did not find the satellites for at least 6 minutes, and once it did the boat icon flipped every 30 seconds by 16 degrees.

However, now I have two additional pieces of information in this puzzle. After waiting for about 6 minutes for the gps to find the satellites (the GP320B), I decided to go into the installation wizard to the port monitor for the GP320B ( the first 0183 port on the MFDBB) and see if any data was coming in from the GP320B. Sure enough when I turned on the port monitor, data showed up on the screen. I could see in the data what looked my current lat and long. As far as I could tell the data looked reasonable, although I couldn't decipher all of the sentences. The interesting part of this is that when I backed out of the installation wizard and NN3D booted up again, it found the satellites in less than a minute.

Possibly it was cooincidence but also possibly it was due to running the port monitor on the first 0183 port for the GP320B. I don't think it was simply a result of going into the installation wizard and back out again, since I have done that quite a few times when this problem first started to happen and it never made the gps spring to life before. I only have tried this once. I hope to get on the boat today and try it again. So maybe there is something going on in the MFDBB where it isn't properly listening to the 0184 port (Data In I think), and somehow running the port monitor gets it listening properly.

The second piece of new info is that I turned off the GPS200 from sending the Magnetic Variation Sentence. When I did that the NN3d stopped flipping the boat icon every 30 seconds, but the NN3D still managed to get the boat icon pointing the correct direction, so it must be getting magnetic heading information from somewhere else. Do you know if the GP320B sends it out, or does the NN3D just have a static table lookup if it doesn't see that info on the NMEA 2000 bus?

The GPS200 is sending out the magnetic variation every second. When I am on the boat later I will try increasing that rate to every half second to see if it makes a difference. It would be useful to know what algorithm the NN3d uses to find the magnetic variation data. Does the FA50 output magetic variation?

The GP320B provides magnetic variation; as do must GPS units. It sounds like you either have a unsuitable source of heading connected to the system or one of your ports "checkmarked" for heading without suitable heading connected to that same port.
As I said before
As far as the pointing of the boat, when you have heading data (like from your Simrad) the icon uses heading (by default) NOT COG to point the boat. Check under your ship and track ICON and see that the boat pointing is set to heading.
You need to see if it is a COG or Heading issue. When this problem occurs, try changing the setting under ship and track to the other setting. (ie. if set to heading, change to COG) and see what happens.

When it comes to GPS (includes COG) the system has a priority system.
1. Network data
2. NMEA 2000 data
3. NMEA 0183 data

The system will use what you have selected in the wizard under GLOBAL - DATA SOURCES until there is a problem with the selected source, then it will follow the priority system until it finds a GPS source. By the sound of it, your problem is more with a heading issue than a GPS issue.
Johnny Electron,

Thanks for the detailed reply. I had the installer on the boat again on Friday. He contacted Furuno Tech support and they suggested turning on the Magnetic Variation output pgn on the NMEA2000 bus. That fixed the boat icon flipping problem ( he also turned off the GPS200 from outputing the magnetic variation). That might make you think that there was a problem with the gps200 magnetic variation.

However, he also noticed that the GPS Status screen on the NN3D where it shows the satellite strengths was blank. He also brought along another GP320B gps receiver. When he plugged that receiver directly into the back of the MFDBB and restarted the NN3D system the gps came online immediately, and the GPS status screen showed satellite receive strengths.

From this we concluded there there is something wrong with the GP320B on the boat, so he replaced it with the new one that he had brought. That fixed the GPS startup delay problem. Now the system starts up and the gps is valid immediately and the GPS status display shows satellite strengths.

Possibly some kind of flakey behavior in the GP320B was causing both the 16 degree flip every 30 seconds as well as the slow gps lock at startup. I went back into the installation wizard and put it back to the way it was by turning off sending the magnetic variation on the NMEA 2000 bus, and I reset the gps200 to send magnetic variation. Everything still works fine. It looks like changing out the GP320B fixed both problems.

I am cautiously optimistic that the problem is solved, but I will keep an eye on it to see if comes back.

It is good to know that the GP320B puts out magnetic variation and that the system searches for GPS sources when the configured one under data sources goes away. When you say Network data in your list below, which network are you referring to - ethernet? - in which case it would pickup the FA50 next I guess.

Is there anyway to tell when the NN3D has switched over to a different gps receiver when it has detected that one has failed?

When you say Network data in your list below, which network are you referring to - ethernet? - in which case it would pickup the FA50 next I guess.


Is there anyway to tell when the NN3D has switched over to a different gps receiver when it has detected that one has failed?

If you lose the GPS during operations, you will be given a warning "POSITION DATA SWITCHED". If it happens before you power on the system, it will seek out a source, and there will be a delay on getting position data.

It is VERY rare to see a GP320B go bad. Ensure you do not have it mounted in range of a transmitting device/antenna or storing it sideways or upside down. (The GP320 is only protected from water in the upright position)
Hi Johnny E,

I think that the GP320B is mounted correctly, right side up etc. It is mounted on top of the roof of the flybridge. My boat is one of many with similar configurations, so I think it is probably correct. Two installers have looked at it and not mentioned any installation issues but I can check with them on it( just sent an email).

As far as being near a transmitter, the only thing transmitting up there is the FA50 antenna, which I guess only sends every few minutes or so. There is also an ethernet bridge antenna but I can power down that device so that it doesn't send or receive. I have tried booting the NN3D with that device either on or off and not seen any differences, although I think I may have seen some interference when I get near the marina on the way back. Sometimes I lose position data for a while when nearing the marina, and this is presumeably when the ethernet bridge is trying to reconnect to the marina WIFI. - but I haven't seen a problem on normal NN3D startup. I also haven't verified that losing the position data when returning to the marina is due to the ethernet bridge transmitting. It is just a theory at the moment. I need to experiment by turning the bridge off once I leave port and then check if I lose position data again when returning.

Anyhow, with the new GP320 in there the gps comes up immedately which it didn't do before.( with or without the bridge on). Best case before was about 30 seconds, worst case 15 minutes. In the meantime the lat and long would be 0,0 which would always put the NN3D system off the coast of Africa, where 0, 0 lat/long is located and there is no map data, so the screen would be an even grey color. Then once the gps found the satellites I would have to press the "Ship" button to get the map centered on the boat properly.

How long does the NN3D take to find the FA50 once it has determined the GP320 is down?
I have had a few cases where the NN3D "loses position data" for maybe about 5-10 minutes ( I didn't time it). In the meantime I started up my PC nav system, which runs off the GPS200 Maretron receiver, and that worked fine. Eventually I noticed that the Furuno gps had found the satellites again, but there was no obvious indication which receiver it was using. Possibly it had failed over, or possibly it was still using the same receiver?? It was quite a long time though. ( 5-10 minutes seems long when you want to see exactly where you are in a channgel :) ).

I am convinced that you have fixed your problem (at least for now) when you replaced the GP320B. When you deal with GPS antennas, it is very important that you place them where other RF doesn’t Jam or damage them. In your case, I am worried that your problem will stay fixed until the new GP320B starts showing signs of damage. The GPS antenna needs to be 3 feet (min.) away from your VHF or transmitting AIS antenna (About 4 meters from HF.) I would be really concerned in your case, with that Ethernet bridge antenna you have. It should not be anywhere near your GPS antenna. I have seen boats where Wi-Fi and cell phone boosters have jammed GPS of nearby boats. It isn’t a matter of turning off the booster when not being used, because when it is being used it is slowly damaging the GPS sensor. Once the damage is done, it’s done. The first thing a GPS sensor does is amplify the weak satellite signals. When you put a strong source of RF to the GPS, it damages the front end amplifier of the GPS slowly to the point that you start having more and more problems getting a fix. I hate to say it, but I think this is your problem. Time will tell, but if changes to the boat are not made, I would expect you to be replacing the GPS again at about the same time interval as before.

How long does the NN3D take to find the FA50 once it has determined the GP320 is down?

It depends on how much equipment is connected to the system but it can take up to 4 mins for the switch to happen.
I need to look at the antenna locations again. I don't know exactly how far the WIFI antenna is from the GPS at the moment. What is the recommended distance there? I'll check with the installer to see if he has seen any issues on other boats with gps failures related to the WIFI antenna.

I performed an experiment on the boat today, by unplugging the GP320B and timing to see how long it took the NN3D to find the next GPS source. At 11.5 minutes, the NN3D found another source - stopped reporting "Postion Data Missing" ( I guess the FA50 was found based on your search order list below ). Also at this point, the boat icon started flipping again every 30 seconds by 15 degrees which was interesting.

This suggests to me that my original problem was basically a total failure of the GP320, and it took 10-15 minutes at initial startup of the NN3D for the NN3D to run through its protocol to find a backup GPS. When it did find another source - the FA50, I guess the Magnetic Variation PGN needs to be turned on on the NMEA 2000 bus from the NN3D, to avoid the 30 flip of the boat icon with this gps source.

I don't think you have ever said. Are you setup to point the boat by "Heading" or "COG"?
When the problem occurs, if you change the setting to the other type; what happens?

I have an FA50 and when used it as a position source, it doesn't flip. The only flipping I have seen in the past with the NN3D, is normally caused by a poor heading source or bad setup of checkmarks in the installation wizard. For example Furuno sells the PB150 weather unit. We have the heading sentence turned off by default because it isn't good enough for the NN3D and normally results in flipping of the boat icon.

Your Position switching is also taking a very long time. If this was a MFDBB, I would swear someone had upgraded the software while it was setup as a master. (Which is a No, No)

Your problem is going to need to be looked at deeper; even though your GP320B fixes the issue. I would recommend that you open a support case (SUPPORT - ASK FURUNO A QUESTION) and attach your system drawings so that we can have an engineer look over what might be happening with your setup.
Hi Johnny E.

The setup for the boat icon is Heading not COG. I am pretty sure that I changed it to COG and it still flipped every 30 sec since it was such an easy thing to change and didn't require going into the installation wizard, but I can't say for absolute certainty. I can try that by recreating the problem by disconnecting the GP320.

The RC42 is putting out heading every 5 milliseconds - I checked this with an actisense data logger plugged into the NMEA 2000 bus. I don't see any real changes in the heading value after looking at the log file. I thought that there might be a bad value in the transmission but no.

When you say "your position switching is taking a long time", do you mean the time to switch to another GPS?

This is an MFDBB - I don't get your comment about upgrading the software when it is setup as a Master - which this unit is setup as. Maybe that is the problem. How do I fix that?
Most likely this unit was upgraded while it was the master. There is another MFDBB on the fly bridge.

For system drawing do you mean the Connection Diagram that is available from the System Menu?

When you say "your position switching is taking a long time", do you mean the time to switch to another GPS?

Yes, that is exactly what I mean.

This is an MFDBB - I don't get your comment about upgrading the software when it is setup as a Master - which this unit is setup as. Maybe that is the problem. How do I fix that?
Most likely this unit was upgraded while it was the master.

When a black box processor is COMBO upgraded, it is VERY important that is NOT be done when the "MASTER" setting is "ON". If it is COMBO upgraded, when the unit is setup as “MASTER”; the unit will work, but things will be slower than normal and “strange” things happen. (To Fix this; you basically need to factory reset the BB unit and reconfigure it)

LINK TO THE COMBO UPGRADE INSTRUCTIONS FOR THE BB: (STEP 3 is very!! important) ... 0v2.07.pdf

For system drawing do you mean the Connection Diagram that is available from the System Menu?

No, I mean the drawing(s) the installer should have drawn up showing what equipment is involved in this system and how everything is interconnected.

Please check what happens when you change the setting for the boat icon. It would be helpful information to know. Heading = flip/no flip COG=Flip/no flip
Please also try both of these combinations when your heading (Bearing) is set to display in TRUE and then again in MAGNETIC.

The more information we can provide the engineer the better.
I ran a few more tests today to see how fail over worked and to check on the 16 degree flip every 30 seconds.

1st Test:
I configured the FA50 to be the GPS src and Time/Date src in the installation wizard. When the NN3D system restarted the GPS worked immediately and everything looked good - no 30 second flip. Note that I had disabled all the PGNs from the GPS200 so there was no chance it could affect anything during this test. However the interesting anomoly is that the GPS satellite status screen showed no satellite status information. Apparently the FA50 does not transmit satellite status info. I looked around under the FA50 config, but could find nothing to change that would turn this on.

2nd Test:
I set the GP320B as the GPS and TIme/Date src in the installation wizard and backed out. The NN3D came up normally with GPS immediately and the GPS status screen showed the satellite status's. Then I disconnected the GP320B wire to the MFDBB to see how failover worked. After 10 seconds the NN3D reported "Position Data Lost", then after about 2 minutes it failed over the the FA50. I did this twice and both times it failed over in about 2 minutes. I could tell it was the FA50 because the GPS status information was blank and because I had the GPS200 PGNs disabled so it wasn't transmitting any Lat/Long.
Note that the Boat icon and heading line were stable with no flipping every 30 seconds.

3rd Test:
This time I turned on the GPS200 PGNs and I went back into the installation wizard to set the GPS and date/time to the GP320B - which it was already set to from the previous test, but when backing out the NN3D would reconnect to the GP320B not the FA50. So again after the NN3D system was up, I pulled the GP320B cable out. At 10 seconds the system reported "Position Data Lost". Again in about 2 minutes the NN3D system found the FA50 and the GPS position was correct again. As before the GPS status screen showed no satellite status information. However this time the boat icon and heading line flipped every 30 seconds by 16 degrees. The key difference is that the GPS200 is now enabled to send out its magnetic variation in the test, but was turned off in the two previous tests.

I changed the boat icon to point using COG instead of heading and then only the green heading line rotated 16 degrees every 30 seconds. The boat icon stayed put pointing straight up. Using either magnetic or true north made no difference. In both cases the heading line always flipped 16 degrees every 30 seconds, and the boat icon only flipped if it was set to heading instead of COG.

4th Test:
This time the test was to see the fail over time to the NMEA 2000 bus gps - namely the GPS200. I powered off the FA50 and went into the installation wizard to set the GPS to the GP320B, which it was still set to. Backing out the NN3D system found the GPS immediately and the GPS status screen showed satellite info correctly. I unplugged the GP320B, and it took 17 minutes to find the GPS200. I did this test twice and both times it was 17 minutes.
The GPS status screen did show correct satellite status information when it failed over to the GPS200 ( as compared to the FA50 where it didn't). 17 minutes is a really long time. I even checked that the FA50 was really off, by looking at the status LEDs on the front. They were all off.
During that 17 minutes even with the position data missing the boat icon and heading line flipped every 30 seconds.

5th Test:
This time I set the GPS 200 to be the GPS source in the installation wizard. When the NN3D system came back on line it found the gps immediately and the satellite status was valid as well. However the boat icon and heading line still rotated 16 degrees every 30 seconds. I tried turning on the Magnetic Variation PGN in the installation wizard for the NMEA 2000 bus, but that didn't appear to have any effect. For some reason using the GPS200 for magnetic variation causes a flip in the heading data every 30 seconds. I meant to alter the rate that the GPS200 sends that data. I think it sends the magnetic variation once a second by default. I thought I would try 500ms or faster but I forgot to try that. Maybe it would have an effect?

So the fail over to the FA50 from the GP320B works pretty quickly - around 2 minutes. I'm not sure what happened the other day when it was 11 minutes. Fail over to the NMEA 2000 GPS200 is very slow at 17 minutes. The 30 sec flipping seems to be coming from the GPS200 magnetic variation data. I tried resetting the GPS200 to factory defaults using the N2K analyzer, but it still flipped after that.

Maybe we need to try plugging in another GPS200, although it doesn't appear to be having any problems reporting its data to the Maretron DSM200 display.
I also noted that the GPS200 found three additional satellites compared to the GP320B. The GPS200 found 4,12,2,9,27,135,17,25,14,10,20,28 whereas the GP320B found 2,4,9,10,12,14,17,25,27. I don't know if this is significant or not.

Great job on the testing! :respect
The only additional thing would have to been to check to see if there was a change when running in TRUE HEADING versus MAGNETIC HEADING.

It is no doubt that something from your Maretron GPS200 is causing the boat HEADING to flip. I say "HEADING" because when you use COG to point the boat (with the Maretron having the sentences on) the boat icon doesn't flip. Only the heading line (which is based on heading info) does. You might contact Maretron to see if they have newer firmware available for your unit. If not, then you would need to keep those sentences "off" , if you plan on keeping the GPS200 connected to the Furuno system.

You are correct the FA50 AIS unit does not provide satellite status to the NavNet. This is because the GPS data of the AIS is for the AIS unit to use and really not intended to be used as a primary GPS source. It does put basic position to the network and makes for a good basic source of GPS data for redundancy. I never recommend using FA50 AIS unit as your primary GPS source.
True Heading versus Magnetic: there was no visible difference using one or the other. In either case the heading line flipped, and the boat icon flipped if it was set to heading.

From past tests if I turn off the magnetic variation PGN on the GPS200 then the heading line does not flip. I'm not sure what the NN3d would use for magnetic variation in this case since there would be no source of it, assuming that the GP320 was disconnected and the FA50 was off. I seem to recall doing this test quite a while ago and the NN3D did eventually get the heading pointing in the correct direction ( without a flip ), but there was a bit of delay getting the heading line pointing the right way on startup of the NN3D.

Is there is a static lookup of magnetic variation based on GPS latitude in the NN3D when magnetic variation is not available from a GPS?

I may just turn off the magnetic variation PGN on the GPS200 and leave it off.

I'll ask the installer if he knows of any updates or issues with the GPS200. I believe he is well versed in Maretron equipment.

Jim & Johnny: this has been a very interesting & worthwhile post. The suggestion I would like to make is for future product enhancement: it would be great if we could see easily just what GPS source is being used. Getting the 'Position Data Lost" message is fine in itself, but it is desirable to be able to see what the next-selected gps sensor is, as more and more gear is providing gps data as a by-product of its main function.
Agreed, it is a good suggestion. I will pass it on. The new TZT system does show what is being used; if the primary isn't. It would be a useful change to the NN3D.
I guess you can infer whether its switched to the FA50 by clicking on the gps sensor icon in the upper right and checking if any satellites show up in the GPS Status display. If not, its the FA50.
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