[gpsd-dev] ABVDM sentences from AIS

[Iván Sánchez Ortega]

Hi all,


Since a few days ago, I'm getting some AIS messages starting with ABVDM, as 
opposed to the much more common AIVDM and BSVDM. They all are decoded the same 
way.

A bit of background: "AIVDM" is split into the "Talker ID" ("AI") and the 
"Sentence formatter" ("VDM"/"VDO"). An "AI" talker is a "Mobile AIS station" 
(a boat), and "BS" is a "Base Station" (big antenna on ground).

As far as I'm aware, with the introduction of NMEA 4.00 the talker ID "BS" 
will disappear and will be replaced by either "AB" or "AD" and maybe "AT" and 
"SA", plus there will be "AN" (buoys) and "AX" (repeaters).


I had a look at the code, and if I understand these lines correctly...

http://git.savannah.gnu.org/gitweb/?p=gpsd.git;a=blob;f=packet.c;h=363b8e5548b57ab92a11a8a0caeda4f5a904d6cb;hb=HEAD#l1504
 

...then there's no support for that yet. My C skills are not that good, but 
even I can copy-paste that code to support ABVDM/ABVDO.

I wonder if the right way to go is to treat **VDM and **VDO messages as AIS no 
matter the talker ID, and I wonder if having the talker ID in the outputted 
JSON would be of any practical use at this point.


Any thoughts?


Cheers,
-- 
Iván Sánchez Ortega <address@hidden> <address@hidden>

Web & geospatial developer at Aptomar AS