Garmin AIS with OpenCPN

[PaulRainbow]

I recently fitted a Garmin VHF 300i AIS balck box VHF to my boat as part of my updating process. Not fitted a new plotter or NMEA 2000 network yet, but amongst my collection of electronics i had a Shipmodul multiplexor with Bluetooth. I already have OpenCPN on a laptop using VMH charts.

Over the past couple of days i've been keeping an eye on the AIS overlay and i have to say, i'm not at all impressed. Lots of vessels just don't ever show, there is a row of container ships across the river at Felixstowe and only one or two of them show. I've also monitored traffic using an app on my tablet, which is surprisingly accurate. The tablet shows vessels traveling through Harwich haven that are not displaying on OpenCPN at all.

I watched the Stena Hollandica come into Harwich earlier and there was a point where the AIS data for her didn't update for 8 minutes ! Pretty rubbish when she's traveling at 8 knots and is going to to pass within 0.6nm. Whilst the data for that ship was not updating, other vessels of lesser importance were.

The multiplexor has a LED that flashes when receiving data and it doesn't seem to flash much, so i'm suspecting the Garmin unit. It's not my antenna, as i have two and it's the same on both, normal VHF works fine.

Here's a list of data received over a short time :

!AIVDM 1 1 B 13P<2j@P?w05rHTMfGhf4?wb0<15 0*54 22:00:08
!AIVDM 1 1 A B3P7MNh0081M2@WL1uc:cwrUoP06 0*61 22:00:08
!AIVDM 1 1 A 13P;Q20P0jP60DvMfB1eOwvT2@:> 0*23 22:00:30
!AIVDM 1 1 B 13P=Dq0Okq0615`Meg@<>b0P00S7 0*13 22:00:31
!AIVDM 1 1 B 13aJmt000lP5k;6MfMaS9Ri<0<1Q 0*4C 22:00:53
!AIVDM 1 1 A 15B7>:000iP60>4MfECMSJa<0PS7 0*76 22:00:53
!AIVDM 11 B 13P=Dq0Okj060@<Mel8ddbC>00S9 0*6E 10/06/2016 22:00
!AIVDM 1 1 B 13P8bi@000060t6MfPEMHJj22H0W 0*74 22:00:54
!AIVDM 1 1 A 13P=Dq003k05wVtMepvdg4080l 0*47 22:00:54
!AIVDM 1 1 B 35AH2`5000P5pQJMfwuhvSun0Dg: 0*25 22:00:54
!AIVDM 1 1 A D02=VV@@HN?aRLN00SuNfp0 2*19 22:00:54
!AIVDM 1 1 B 13P=Dq0Okk05wS<MeqJ<g:F6081p 0*56 22:01:18
!AIVDM 1 1 A 15B7>:000iP609NMfFR=LbT40p1T 0*42 22:01:18
!AIVDM 1 1 B 4h2=aLAv1UF32P5Su6MaCIo006h< 0*11 22:01:18
!AIVDM 1 1 A D02=VVAThN?`b<N01pENfp0 2*7F 22:01:18
!AIVDM 1 1 A 15B7>:000iP604JMfGgMGl0l3H 0*02 22:01:19
!AIVDM 1 1 A 13P7AI?P00P61AdMfOcf2?vl20RO 0*3F 22:01:19
!AIVDM 1 1 A 13P<2j@P?w05rH@MfGhf4?vn00S; 0*2E 22:01:19
!AIVDM 1 1 B 13P=Dq0Okq05w74MewF=h;2p0<1; 0*58 22:01:20
!AIVDM 1 1 B 19NWvEP00w05sQ:MffBEm4Tp00Sb 0*3B 22:01:20
!AIVDM 1 1 A 13aJmt0uhkP5kfdMfMk38Bfn0<1s 0*5E 22:01:21
!AIVDM 1 1 B 13454`002BP6Wb`Men;k8jPn06h< 0*19 22:01:21
!AIVDM 1 1 B 13P<2j@P?w05rH@MfGhf4?vr0H@e 0*04 22:01:21
!AIVDM 1 1 A 13P7ULP00005rNPMfHRafA0r0@@w 0*21 22:01:44
!AIVDM 1 1 B 13P=Dq0Okr05w5PMf0Iem;9006h< 0*34 22:01:44
!AIVDM 1 1 A 13P=Dq0Okq05w68Mewq=jc4t0<1< 0*3E 22:01:44
!AIVDM 1 1 A 13P=Dq0PCr05w0<Mf6H=oc3d0HOC 0*14 22:02:08
!AIVDM 1 1 B 13P<2j@P?w05rH@MfGhf4?wb06h< 0*1A 22:02:08
!AIVDM 1 1 A 13P;JVhP1G05u?:MffMTl?wb0D2M 0*71 22:02:08
!AIVDM 1 1 A 13P;Q20P0hP6042MfH;=DgvT28:> 0*2E 22:02:30
!AIVDM 1 1 B 13P=Dq003n05vj8Mf<:=NbjP0D1E 0*05 22:02:31
!AIVDM 1 1 A 402=VVAv1UF4>P62>8MetVo0088u 0*70 22:02:31
!AIVDM 1 1 A 19NWvEP01905t7pMfaTUeTI<0<33 0*59 22:02:31
!AIVDM 1 1 A 15B7>:000hP5wkbMfK:u8b?<0`F= 0*4D 22:02:31
!AIVDM 1 1 A 13P<2j@P?w05rH@MfGhf4?w>06h@ 0*39 22:02:31
!AIVDM 1 1 B 13aJmt000pP5lTdMfN536jg<06h@ 0*26 22:02:31
!AIVDM 1 1 B 13P=Dq003n05vJHMfBBeL:k>0<1F 0*45 22:02:32
!AIVDM 1 1 B 33454`0PB?P6aq:Mepgjej5>00bQ 0*43 22:02:32
!AIVDM 1 1 B 13P7ULP00005rNJMfHSb;i3@08G; 0*4D 22:02:32
!AIVDM 1 1 B 13P8bi@000060sBMfP@uHJk@2D1b 0*71 22:02:33
!AIVDM 1 1 A 33454`0PB=P6bVVMer`RD1f:0000 0*29 22:03:19
!AIVDM 1 1 B 13P<2j@P?w05rH@MfGhf4?wB0<15 0*60 22:03:19
!AIVDM 1 1 B 13P=Dq003j05u;0MfMCdHb4n06hD 0*46 22:03:41
!AIVDM 1 1 A 15B7>:000fP5wTpMfMGLlb6l0d3E 0*28 22:03:41
!AIVDM 1 1 B 13P;Q20P0P5wkVMfKQ=7Ovp26hD 0*0A 22:03:41
!AIVDM 1 1 A 13P=Dq0PCd05tD0MfQ8cO8wT0<1K 0*3D 22:03:42
!AIVDM 1 1 A 13aJmt01A<P5ma0MfNR37jaP0@Lq 0*16 22:03:42
!AIVDM 1 1 A D02=VV@dPN?avTN0105Nfp0 2*3B 22:03:42
!AIVDM 1 1 A 33454`002;P6cS`Mew@QQQ=R00V0 0*0B 22:03:42
!AIVDM 1 1 A 13P7ULP00005rNDMfHRb7i3T00SF 0*38 22:03:43
!AIVDM 1 1 A 13P8bi@1h0060sdMfPK=HJkT2HMN 0*06 22:03:43
!AIVDM 1 1 A 13P<2j@P?w05rH@MfGhf4?wV08Ma 0*5B 22:03:43
!AIVDM 1 1 A 15B7>:000fP5wKvMfNGtd:5T0hMI 0*1F 22:03:43
!AIVDM 1 1 B 13P=Dq0PC`05t=hMfQ@:t8UV06hD 0*7D 22:04:06
!AIVDM 1 1 A 13P=Dq0PCW05t7<MfQ@:K`5d0@OC 0*74 22:04:06
!AIVDM 1 1 B 13454`002;P6cV0MewOiPQ;V0L<O 0*02 22:04:06
!AIVDM 1 1 A 15B7>:000eP5wBrMfODtdJ4L0d3C 0*02 22:04:07
!AIVDM 1 1 A 13P<2j@P?w05rH@MfGk>4?vN00SA 0*2F 22:04:07
!AIVDM 1 1 A 13P=Dq0PBR05s?TMfNG8m7<R0<1K 0*49 22:04:30
!AIVDM 1 1 A D02=VVA8`N?`>4N01L=Nfp0 2*0B 22:04:53

That doesn't look like a lot of data, considering the area i'm in. Looking right now, there are 10 vessels missing in the Harwich haven, compared to the tablet app.

Anyone use either the Garmin AIS or OpenCPN have any thoughts ?

 

[bitbaltic]

Edited comment on timeframe- just noticed the time stamp. That's just short of five minutes of data so it's probably not a long enough timeframe to include all moored vessels etc. Class A ships at anchor update position every 3 minutes and static data only every 6 minutes, so you might want to record at least 6 minutes of data to get a representative sample if you/they are in port in case you miss any transmissions. Remember !AIVDM uses binary encoding (unlike regular NMEA) so there is more data in there than it might look like.

Couple of thoughts:

1) I don't know which Shipmodul you have or how you go about configuring it over bluetooth, but are you sure it is running at the optimal speed (likely to be 57600 or higher) for the connection to the PC. Are you sure the AIS box is connected to its 38400 port (and that it has a 38400 port to begin with).

2) I do see differences between various bits of software I use to display AIS- in my case Seatrak is slower and displays less targets than PC Plotter. I get the best target display performance (number and speed) from NavMonPC. Sugest installing NavMon and seeing how its AIS display compares to what you are seeing in OpenCPN.

The above might help rule out issues in the PC downstream of the multiplexer. If no difference then as you say you will have to look upstream.

Edited to add: FYI a class A ship travelling at 8kn should update its SOG every 10 sec on a dual channel receiver, but its static info again only every 6 min, so do check what data you were expecting to be updated for the 8 minutes the Stena vessel seemed to not be received. It's close to the timeframe of the static update.

 

[HunterWanderer]

I have a nasa ais engine and the baud rate is 4800 from the gps and 38400 out to Opencpn.
Try setting both the baud rates on the com port properties ( using the computers device manager ) and set the data connection port in OpenCPN to the same rate ie 38400

 

[RichardS]

I've never noticed any difference between OpenCPN with CM93 charts and the various apps I use on my tablet. I'm connecting the laptop and the tablet to the AIS transceiver by wifi.

Richard

 

[PaulRainbow]

Edited comment on timeframe- just noticed the time stamp. That's just short of five minutes of data so it's probably not a long enough timeframe to include all moored vessels etc. Class A ships at anchor update position every 3 minutes and static data only every 6 minutes, so you might want to record at least 6 minutes of data to get a representative sample if you/they are in port in case you miss any transmissions. Remember !AIVDM uses binary encoding (unlike regular NMEA) so there is more data in there than it might look like.

That data was from yesterday, i did record a lot more, just posted an extract. I've had it running for hours without it picking up all the vessels.

1) I don't know which Shipmodul you have or how you go about configuring it over bluetooth, but are you sure it is running at the optimal speed (likely to be 57600 or higher) for the connection to the PC. Are you sure the AIS box is connected to its 38400 port (and that it has a 38400 port to begin with).

It's the Miniplex 42BT. AIS sends at 38400, multiplexor sends over Bluetooth at same speed, PC port also set to 38400.

2) I do see differences between various bits of software I use to display AIS- in my case Seatrak is slower and displays less targets than PC Plotter. I get the best target display performance (number and speed) from NavMonPC. Sugest installing NavMon and seeing how its AIS display compares to what you are seeing in OpenCPN.

Will give that a try, thanks.

Edited to add: FYI a class A ship travelling at 8kn should update its SOG every 10 sec on a dual channel receiver, but its static info again only every 6 min, so do check what data you were expecting to be updated for the 8 minutes the Stena vessel seemed to not be received. It's close to the timeframe of the static update.

I was expecting to see some more regular updates of autonomous dynamic data, notable where the 240 odd metre ship actually was would have been nice. By the time i got a position update it have traveled through Felixstowe. :ambivalence:

 

[bitbaltic]

It's the Miniplex 42BT. AIS sends at 38400, multiplexor sends over Bluetooth at same speed, PC port also set to 38400.

Ok. how have you made the connections? From the 42BT manual:

The speed of the listener ports is fixed to 4800 Baud (= bits per second), which equals 480
characters per second

So if the AIS is connected to one of the regular input ports it will be a data bottleneck.

The manual says to connect an AIS to the RS232 port (pin 3 rx+ and 5 COM- of the serial port) and set the multiplexer to AIS-mode using the MPX-Config utility on the PC.

AIS mode: This mode is used to connect an AIS receiver running at 38400 baud. The AIS
receiver must be connected to the RS-232 port of the multiplexer (RxD and COM
only) while the computer must be using the Bluetooth interface. The
communication speed of the multiplexer must be set to 38400 baud. The
multiplexer will now send the data received from the RS-232 port to the Bluetooth
channel and to NMEA Out1, unlike in Hub or Server mode, where it is also sent to
NMEA Out2. NMEA Out1 can be connected to a chartplotter like the Raymarine© C
or E series, which can display AIS information.

If you have done the above then check the way the PC is performing by looking at the AIS with NavMon, but if the AIS is just connected to the regular port and/or the multiplexer is not set up in the software for AIS mode, this could be the issue.

If all of the above is already correct then the problem might be the aerial(s) as you are running out of options....

 

[PaulRainbow]

Thanks for the replies.

I've got the AIS connected to the serial port on the multiplexor, the Bluetooth output will only send at 38,400. Everything else is set to 38,400.

Was up til about 3am messing around with this. Checked, double checked, gazillion checked all of the settings. Tried NavMon, looked the same as OpenCPN.

The bluetooth receiver is connected to a USB hub, which is also supplied with independent GPS data, then to the laptop via a cable. I wondered if this might be causing the issue, so left the GPS feed via the hub and connected the bluetooth receiver straight to a USB port. This worked fine.

Curious as to which part of the USB setup was causing the problem i did som experimenting and finally ended up back to where it was yesterday, but with everything working s it should. It could have been a bad connection.

Only other thing that's changed from yesterday, i noticed late in the day that my batteries were a bit low, i normally leave the mains charger off and the solar panels keep the batteries charged. I left them on mains charge overnight and they are all fully charged today.

The LED data light on the multiplexor is now flashing a lot more than it was yesterday. Hard to see how a bad USB connection could affect that as the USB stuff is after the bluetooth output of the multiplexor, no physical connections as such. Perhaps a low voltage would cause it. Will monitor it over the next few days and let the batteries run down a bit to see if i can replicate the problem.

Now it's working i'm getting all of the vessels, with names, inside 3 mins. Seen some pilot boats traveling in and out at high speed and they are updating every 2 seconds, as they should.

Saw a SAR aircraft this morning, first time i've seen one of those on AIS.

 

[bitbaltic]

Gremlins. Good to hear it's working now.