Mysteries of AIS

[Howler]

I noticed that the AIS data broadcast by certain Class B vessels includes the vessel name and certain characteristics such as length, draft, etc.

We have a B&G NAIS500 and NSPL500. Other vessels only see our MMSI number, position and speed. No vessel name. No length/draft, etc. This data appears correctly configured using the NAIS Configurator.

Furthermore, although not a reliable source of truth, MarineTraffic hasn't updated our position in weeks.

Any suggestions for:

(a) How to broadcast the vessel name and characteristics?
(b) How to get MarineTraffic and other similar trackers to update our position every few days

Thanks!

[CaptTom]

Originally Posted by Howler

(a) How to broadcast the vessel name and characteristics?
(b) How to get MarineTraffic and other similar trackers to update our position every few days

(a) This is going to be device-specific. Check the vendor's manuals and see if there are any firmware updates. This should certainly be a normal part of the broadcast AIS packet.

Note: Static data like name is broadcast less frequently than dynamic data like speed and position. Be sure you've let it "soak" long enough for the receiving station to get around to receiving the static packets. At longer ranges or if the transmitter is weak (marginal antenna cabling for example) it can happen that only occasional packets are received. Then it takes even longer before the lucky successful packet contains the static data.

(b) You have to be in range of one of their receivers. These are usually placed in or near the mouth of busy harbors. It's not unusual to see your own last position around the time you entered or left port, but nothing before or since. The paid satellite options may or may not be better with Class B transmitters.

[AA3JY]

..have been using an eAIS program like ‘OnCourse’ via Starlink has provided more consistent data updates than being received by the usual and sometimes lacking RF based land stations.

[Tin Tin]

Some older chart plotters do not show additional details like name.


Basic free Marine Traffic app is not satellite based and requires your position to be updated via a VHF base station that is within range. If you load the "On Course" app to your phone, load you MMSI into the app then you can report your position by wifi if within cell range. So in some parts of the country there is a cell tower in range but no VHF station in range and vice versa.


I have not paid to subscribe to the satellite service so don't know how comprehensive it is, but I understand that satellites can pick up VHF broadcast positions so maybe this is what they do. I imagine Starlink changes this a bit but costs.

[rslifkin]

If Marine Traffic isn't picking you up, but it's picking up other boats nearby, I would suspect you have a signal strength problem and are transmitting a weak signal. Poor signal quality could also cause some data to come up missing when another boat receives your signal even if name, etc. is programmed into your AIS and should be transmitting.


It might be worth setting up a separate antenna as a test and hooking that directly to your AIS transceiver to get the splitter, masthead antenna, cabling, etc. out of the picture and confirm if it's a signal problem or an AIS problem.

[Howler]

Great input and suggestions. Will investigate further. Thanks!