AIS shipname and callsign presentation

[vincenth01]

Dear forum member,

Does anyone knows how OpenCPN presents the name and callsign in the AIS massages? For example the @ sign seems to be filterd.

All information is very welcome.

Best regards,


Vincent

[nohal]

Vincent...
What exactly are you asking please? Any example data feed you think we interpret incorrectly?

Pavel

[vincenth01]

Originally Posted by nohal

Vincent...
What exactly are you asking please? Any example data feed you think we interpret incorrectly?

Pavel

Some ships have a @ sign in the name and/or callsign. As seen with other software: shipname @@@@@ is only shipname in opencpn. Some transponders were configured with the @ and some with unknown reason (eg default value not overwriten). I wondering if something happen in decoding or presentation layer.

[bdbcat]

vincent...

OCPN filters out '@'. We assume this is a default character in un-configured AIS transponders, and that is really is not intended to be part of the shipname.

Dave

[vincenth01]

Originally Posted by bdbcat

vincent...

OCPN filters out '@'. We assume this is a default character in un-configured AIS transponders, and that is really is not intended to be part of the shipname.

Dave

Dave,

Thanks for your reply!

Are any other characters filterd?

Best regards,


Vincent

[brian192]

Hello,

I've discovered that OpenCPN shows multiple shipnames as "unknown". With my AIS receiver I captured for some time AIS data. This data has been analyzed and there is something remarkable. The AIS message type 5 sentence (which containing the shipname) is not displayed if the AIS version of that message is type 2.

All AIS messages type 5, with AIS version 0 or 1, are being displayed with the name from the messages.

Is OpenCPN incompatible with message type 5 in combination with AIS version 2?

If it is, then:
Does anyone know how I can work around this finding, in such a way that all the names (despite of the AIS version) are being displayed in OpenCPN?

Brian

[Hakan]

Brian...
Your assumption is correct.
The code says:

//          Get the AIS Version indicator
//          0 = station compliant with Recommendation ITU-R M.1371-1
//          1 = station compliant with Recommendation ITU-R M.1371-3
//          2-3 = station compliant with future editions
            int AIS_version_indicator = bstr->GetInt( 39, 2 );
            if( AIS_version_indicator < 2 ) {

So only AIS version 0 and 1 are handled by OCPN.
I may have encountered the same as you for some newer AIS transmitters. A boat I know has a new AIS and I've not seen the name for it but I didn't saved any messages so I can't say for sure if he was message version 2 or 3.
A suggestion would be change to "if( AIS_version_indicator < 3 ) or 4?.
Is there anyone here that can tell if such a change would cause other troubles?
Håkan

[did-g]

Originally Posted by Hakan

Brian...
Your assumption is correct.
The code says:

//          Get the AIS Version indicator
//          0 = station compliant with Recommendation ITU-R M.1371-1
//          1 = station compliant with Recommendation ITU-R M.1371-3
//          2-3 = station compliant with future editions
            int AIS_version_indicator = bstr->GetInt( 39, 2 );
            if( AIS_version_indicator < 2 ) {

So only AIS version 0 and 1 are handled by OCPN.
I may have encountered the same as you for some newer AIS transmitters. A boat I know has a new AIS and I've not seen the name for it but I didn't saved any messages so I can't say for sure if he was message version 2 or 3.
A suggestion would be change to "if( AIS_version_indicator < 3 ) or 4?.
Is there anyone here that can tell if such a change would cause other troubles?
Håkan

2 is ITU-R M.1371-5, differences seem to be minor and the wording is :

1 = station compliant with Recommendation ITU-R M.1371-3 (or later)
2 = station compliant with Recommendation ITU-R M.1371-5 (or later)

In my understanding : a ITU-R M.1371-3 decoder is able to decode a ITU-R M.1371-5 message with some missing stuff.

[brian192]

Hakan & Did-G,

Thanks for your reply. It's good to know that version 2 is filtered hard coded. It saves me a lot of testing. Despite of this good news, I now have to find an alternative or waiting for an update of OpenCPN that supports version 2.

- Are there free alternatives for OpenCPN?
- What is the chance for an update of OpenCPN with support of AIS version 2 in the nearby future?

Brian

[Hakan]

did-g....
I've briefly checked in ITU-R M.1371-5 and for our use of data we can without further changes include AIS version 3 in our message 5 decoder? (Where we are collecting ship static data.)

Do you agree?

Håkan

[Hakan]

Brian
re:- Are there free alternatives for OpenCPN?
Yes, but for me O is outstanding also compared to commercial stuff.

re: - What is the chance for an update of OpenCPN with support of AIS version 2 in the nearby future?
The change is very good. If discussions here come to same opinion I wrote in last post, did-g, Dave or anyone (like me) can edit the code and make a request to change in next release. The "official" way is that for example you make a future request in the Tracker/Flyspray. (See third thread in this forum)

Welcome to the world of OCPN and this forum where all kind of generous people met.
Håkan

[Hakan]

Brian @ all

See also http://www.cruisersforum.com/forums/...ml#post2170169 where this is already discussed.

[rooiedirk]

There should also a few navigational status definitions be added.
I do have some time to make a push request for this, if there is not somebody working on it already.
For the time beeing it should be safe to change the

if( AIS_version_indicator < 2 ) {

in

if( AIS_version_indicator < 4 ) {

it the AIS_Decoder.cpp file and do a recompile.

[did-g]

Originally Posted by Hakan

did-g....
I've briefly checked in ITU-R M.1371-5 and for our use of data we can without further changes include AIS version 3 in our message 5 decoder? (Where we are collecting ship static data.)

Do you agree?

Håkan

Yes I do.

[nohal]

Thanks all..
As the consent seems general, I have just pushed the change into the master branch.
@brian192: If you are able to build from source, "the future is now"

Pavel