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Old 30-04-2019, 05:08   #1
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AIS problems with shipnames

I have my AIS transponder connected to my PC with a NMEA2WIFI bridge.
Everything works fine except one thing:

For class A transponders the name of the ship is not presented in OpenCPN.
At the moment I use the 5.0 versions but I had the same problem with earlier versions of OpenCPN.

For class B transponders everything works fine.

I have opened the NMEA debug window and analysed the data.
For class A transponders the Vessel Name is send in a type 5 packet.
This packet contains Static and Voyage Related data.

Here is an example from the openCPN NMEA debug stream:

<GREEN>14:13:08 (UDP:192.168.4.1:2000) !AIVDM,2,1,5,A,533qvlT00000uCC;;:0=E0T@v2222222222 2221?=h0564U<?03kPQBiCQ88,0*1<0x0D><0x0D><0x0A>
<GREEN>14:13:08 (UDP:192.168.4.1:2000) !AIVDM,2,2,5,A,88888888880,2*21<0x0D><0x0A>

This data packed contains the vessel name CUPIDO but it's not interpreted by OpenCPN.

Does somebody know's a solution for this problem?

Thanks in advance,
Valoroso
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Old 30-04-2019, 05:11   #2
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Re: AIS problems with shipnames

Brand/type of transponder used, please?
And the NMEA2WiFi?
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Old 30-04-2019, 05:23   #3
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Re: AIS problems with shipnames

Thanks for your quick reaction

Transponder: EM-TRACK B-100 (SRT's soft radio technology)
Wifi bridge: vela-navega NMEA2WIFI

https://www.vela-navega.com/index.php/nmea2wifi
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Old 30-04-2019, 05:56   #4
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Re: AIS problems with shipnames

Do the names come up on the AIS Target List (available thru right click menu). If so, then most likely a display issue

Display: Also in the Toolbox AIS tab (under Ships) do you have the box checked to show names at scale 1:whatever is set ?


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Old 30-04-2019, 06:23   #5
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Re: AIS problems with shipnames

I will make a recording this evening.
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Old 30-04-2019, 06:26   #6
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Re: AIS problems with shipnames

Type of responder: Em-trak B100
Wifi bridge: vela navega NMEA2WIFI
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Old 30-04-2019, 06:35   #7
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Re: AIS problems with shipnames

We are using the B100 since 6 years without issues.
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Old 30-04-2019, 06:47   #8
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Re: AIS problems with shipnames

@bcn: How do you connect the B100 to the PC?
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Old 30-04-2019, 07:04   #9
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Re: AIS problems with shipnames

USB direct. The connector at the B100 has tendency to get loose.
A little wedge placed under did resolve it....

But never a difference between Class A and Class B targets.
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Old 30-04-2019, 09:04   #10
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Re: AIS problems with shipnames

Quote:
Originally Posted by Valoroso View Post
.......
Here is an example from the openCPN NMEA debug stream:

<GREEN>14:13:08 (UDP:192.168.4.1:2000) !AIVDM,2,1,5,A,533qvlT00000uCC;;:0=E0T@v2222222222 2221?=h0564U<?03kPQBiCQ88,0*1<0x0D><0x0D><0x0A>
<GREEN>14:13:08 (UDP:192.168.4.1:2000) !AIVDM,2,2,5,A,88888888880,2*21<0x0D><0x0A>

This data packed contains the vessel name CUPIDO but it's not interpreted by OpenCPN.
Neither of your sentences above was decoded correct by this site: https://www.aggsoft.com/ais-decoder.htm
Could it me some copy mismatch?
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Old 30-04-2019, 10:03   #11
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Re: AIS problems with shipnames

Quote:
Originally Posted by Hakan View Post
Neither of your sentences above was decoded correct by this site: https://www.aggsoft.com/ais-decoder.htm
Could it me some copy mismatch?
I was able to decode this with NavMonPc. It is a compound sentence, both parts are required. The first one had a bad checksum (the single digit "1", it should have been "37"), so I set NavMon to fix bad checksums. The second part did have a valid checksum.

NavMon shows these details -
name: "CUPIDO /0"
Callsign: OTY4222
mmsi: 205422290
Length: 1604 ft (converted from meters by NavMon)

Here are the cleaned-up sentences:
!AIVDM,2,1,5,A,533qvlT00000uCC;;:0=E0T@v2222222222 2221?=h0564U<?03kPQBiCQ88,0*37
!AIVDM,2,2,5,A,88888888880,2*21



I stripped out the <GREEN> and the "<0x0D><0x0A>" stuff. Could this, or the bad checksum be the problem?

I couldn't get that website decoder to work, even after correcting the parity. Here's one that did decode it: https://www.maritec.co.za/tools/aisvdmvdodecoding/
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Old 30-04-2019, 10:47   #12
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Re: AIS problems with shipnames

I got the same result with my own parsing software by turning off the checksum test. So it appears for some reason the checksum for AIS message 5 has a bad checksum but the the static message for Class B (message 24, i believe) has a good checksum. Didn't there use to be an option in OpenCPN to turn off checksum validation? It would be helpfull to see what the raw sentence looked like before OpenCPN got its hands on it. Sure miss the HYPERterminal utility.

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Old 30-04-2019, 11:49   #13
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Re: AIS problems with shipnames

Quote:
Originally Posted by jstevens View Post
....
Didn't there use to be an option in OpenCPN to turn off checksum validation?
....
John
It's still there. Click a connection and un-mark the "Control checksum" box.

Thomas
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Old 30-04-2019, 12:37   #14
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Re: AIS problems with shipnames

First I want to thank you all for your contructive help.

Today I did some new experiments.
I think that the issue with the checksum is the most obvious reason for my problem.
It's strange that it only appears with message 5 packets.

When I connect my IAS transponder via USB everything works fine.
I get names for all the vessels.
Here is a message 5 example from USB:

<GREEN>19:56:25 (Serial:COM3) !AIVDM,2,1,7,A,539lu2T00000@?G?3P1@PTa>0a:00000000 0000Q2P533t0Ht0SCiDQ2BRp8,0*0F<0x0D><0x0A>
<GREEN>19:56:25 (Serial:COM3) !AIVDM,2,2,7,A,88888000000,2*2B<0x0D><0x0A>

I also made a log from my transponder data with ProAIS software.
Message in ProAIS:
!AIVDM,2,1,2,A,53aN`ml0000108i<001H4r1HE9<Dp@44h00 0000U1@G256eg04SCiDQ2BRp0,0*73

Is received in OpenCPN as:
<GREEN>19:48:24 (UDP:192.168.4.1:2000) !AIVDM,2,1,3,B,53aN`ml0000108i<001H4r1HE9<Dp@44h00 0000U1@G256eg04SCiDQ2BRp0,0*7<0x0D><0x0D><0x0A>

I'm loosing the last character.
Now I have to find out where I loose it.
Is the line to long for OpenCPN? The prefix is larger with wifi compared to USB)
Or do I loose the last character in the Wifi gateway?

I have to go back to my boat for a new experiment.
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Old 01-05-2019, 06:04   #15
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Re: AIS problems with shipnames

Quote:
Originally Posted by cagney View Post
It's still there. Click a connection and un-mark the "Control checksum" box.

Thomas
I have tried this but un-marking the "Control checksum" box makes no difference.
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