Any AIS experts out there?

GHA

Well-known member
Joined
26 Jun 2013
Messages
12,289
Location
Hopefully somewhere warm
Visit site
Tracks their phone ??? Never heard that one ... not saying it doesn't - just saying I've never heard of it ...

The Network is a combination of Official, Professional and Amateur stations ... along with satelite.
It's free to set up a receiving station in marinetrafic then you can send AIS sentences to a ip address/ UDP port. Doesn't have to be data received from a receiver, you can make your own ais messages. Signalk has an app to do this among other options. Simple to make marinetraffic think a boat is anywhere.
GitHub - SignalK/aisreporter: Signal K Node server plugin to report the vessel's AIS data to MarineTraffic
https://help.marinetraffic.com/hc/e...-Can-I-report-my-own-positions-by-other-means
 

Martin_J

Well-known member
Joined
19 Apr 2006
Messages
4,284
Location
Portsmouth, UK
Visit site
The other thing to remember is that AIS is just a digital data transmission over the VHF frequencies. When therefore a shore based amateur receiving station receives the AIS data signals over the air, it's own processing power which might just be a PC with a USB digital radio receiver has to convert the over the air analogue wireless signal into binary and then decode it into the AIS transmission packet.

If that first part of that conversion (decode to binary) has a problem or if the vessel transmitting the data is perhaps not using a good/certified transmitter, then you can see where inconsistencies might arise.

About ten years ago I found that my MMSI (a 235nnnnn UK allocated MMSI) was occasionally being shown on MarineTraffic at located at a berth in a marina in Mallorca. Over the next few days I then noticed that precisely the same location sometimes showed a Spanish vessel. Upon a closer look, all the last six digits of it's MMSI were the same as mine but the 225 prefix (for Spain) was occasionally being seen on Marinetraffic as a 235 prefix (UK) and thus showing as my vessel. From the website I could also see the receiving station ID.

In that case it was just one digit of the MMSI that was being sent in error to MarineTraffic. I logged a ticket with MarineTraffic via email and they checked and responded quickly.

1714076268786.png

Not long after that the inconsistencies stopped and MarineTraffic updated me again.

1714076322731.png
 
Last edited:

Martin_J

Well-known member
Joined
19 Apr 2006
Messages
4,284
Location
Portsmouth, UK
Visit site
Correction to the above.. I just found the update I added to the Marinetraffic ticket at the time.

It wasn't the second digit that was wrong. It was the last.

1714076534234.png
 

Rappey

Well-known member
Joined
13 Dec 2019
Messages
4,420
Visit site
I Tracked a friend sailing to the caribbean. He turned off his ais while in Cape Verde. Whilst off his ais position moved to amsterdam for nearly a week until it was turned back on in Cape Verde.
 

Martin_J

Well-known member
Joined
19 Apr 2006
Messages
4,284
Location
Portsmouth, UK
Visit site
I have just found why I thought the country part of the MMSI was being incorrectly converted ten years ago.

It was due just eight years ago to a different receiving station converting the country prefix incorrectly (as noticed by a number of members here). Logged with MarineTraffic and shortly afterwards, the issue disappeared.



1714078672330.png
 

vas

Well-known member
Joined
21 Jun 2011
Messages
7,948
Location
Volos-Athens
Visit site
It's free to set up a receiving station in marinetrafic then you can send AIS sentences to a ip address/ UDP port. Doesn't have to be data received from a receiver, you can make your own ais messages. Signalk has an app to do this among other options. Simple to make marinetraffic think a boat is anywhere.
GitHub - SignalK/aisreporter: Signal K Node server plugin to report the vessel's AIS data to MarineTraffic
https://help.marinetraffic.com/hc/e...-Can-I-report-my-own-positions-by-other-means
+1

done exactly that four years ago when I fitted a raspberry pi running Victron OS (VenusOS) on board.
Registered a roaming station with MarineTraffic (free) and been transmitting my position plus via N2K picking what my Garmin AIS600 reads from around the boat and pumps that info as well.
I could v.easily send bogus messages produced on the raspberry for whatever MMSI I want. Just need internet access.

I guess there's a priority intelligence system in MarineTraffic so in case of conflict (which is most likely what happens in OPs case) if one station transmitting is a ClassA ship or a normal/old/fixed station it takes priority over a roaming one transmitting only itself...
Of course could also be an older transmitter from OP boat which was removed/sold on and next person hasn't paid the 20-30quid to remove and replace MMSI.

When you AIS is off and you see your boat appearing elsewhere check which station is transmitting it's position and go and get the details of it in MarineTraffic. You'll most likely find a roaming station, then you could report that to MT.
 

Refueler

Well-known member
Joined
13 Sep 2008
Messages
18,423
Location
Far away from hooray henrys
Visit site
It's free to set up a receiving station in marinetrafic then you can send AIS sentences to a ip address/ UDP port. Doesn't have to be data received from a receiver, you can make your own ais messages. Signalk has an app to do this among other options. Simple to make marinetraffic think a boat is anywhere.
GitHub - SignalK/aisreporter: Signal K Node server plugin to report the vessel's AIS data to MarineTraffic
https://help.marinetraffic.com/hc/e...-Can-I-report-my-own-positions-by-other-means

I've never delved into the nefarious side of this ... been happy with our use of it for tracking our ships ...

Interesting.
 

GHA

Well-known member
Joined
26 Jun 2013
Messages
12,289
Location
Hopefully somewhere warm
Visit site
I guess there's a priority intelligence system in MarineTraffic so in case of conflict (which is most likely what happens in OPs case) if one station transmitting is a ClassA ship or a normal/old/fixed station it takes priority over a roaming one transmitting only itself...
They say there is some filtering >
Seven ways MarineTraffic ensures AIS accuracy
 

Bilgediver

Well-known member
Joined
6 Jun 2001
Messages
8,109
Location
Scotland
Visit site
All thoughts welcome! (I've no idea if this has relevance to the question or not but we're in the Netherlands, not the UK). MK
This can often be a result of incorrect procedures being carried out at the sale of a boat.
The call sign and MMSI should always remain with the ship/boat. Is it possible that whoever sold your boat to you has carried on using the same MMSI on his next boat.
 

MK101

Member
Joined
17 Oct 2017
Messages
38
Visit site
when it's wrong does it show up in the wrong place on both vesselfinder & marinetraffic at the same time? Tried a mmsi number search just to see what comes up?

Also, when it's wrong you can see where the reporting station was in marine traffic, just checked a position of mine sent online & it said in the middle of Holland . It wasn't there 🙂
Indeed is on both systems in the same place!
 

MK101

Member
Joined
17 Oct 2017
Messages
38
Visit site
The problem arises because Marine Traffic not only tracks real AIS transponders but also tracks imaginary ones where a user of the app enters details and Marine Traffic tracks their phone. When your real AIS is transmitting, it takes priority, but I'm pretty sure that the ones you see when not on your boat are generated by someone using the app to generate their own tracking information. They have - probably inadvertently - entered details that match yours. My own boat often shows up at Grimsby or Immingham - she has never been there!

Marine Traffic, at least in the incarnations most of us use, is dependent on a network of amateur receiving stations; I am afraid it is also not unknown for them to inject incorrect data, too.

@Refueler probably has a professional subscription, which will be more robust.
That makes a lot of sense. Thanks!
 

MK101

Member
Joined
17 Oct 2017
Messages
38
Visit site
This can often be a result of incorrect procedures being carried out at the sale of a boat.
The call sign and MMSI should always remain with the ship/boat. Is it possible that whoever sold your boat to you has carried on using the same MMSI on his next boat.
No - they stopped sailing, so it's not the former owners. But it's also true that they never had the same issue. So whatever happened took place after we bought her. Something may have happened when we transferred the details to our names. But the numbers (at our end) are definitely correct - I've checked multiple times!
 

MattS

Active member
Joined
7 Sep 2020
Messages
461
Location
Kent
Visit site
Do you input MMSI ? If so - I would suggest you are unusual in that ...
Agree probably not the norm, but I search MT using MMSI for any vessels I'm familiar with, just to avoid having to click through the multiple results for the same name until I find what I think is the right vessel based on the location it's showing!
 
Top