AIS Tracking?

[Roniszoro]

I just took a 650 mile voyage to Bermuda and my family said that after the first day they were unable to find the boat on the marinetraffic.com site. Days later it showed the boat going in a straight line to our destination. We were in satellite phone contact and when told of no AIS, we assumed that the AIS transmitter was not working. We were able to see other vessels during our journey so AIS receiving was working. As we approached Bermuda, we got a call from Bermuda Harbor Radio calling us by name. So they could see us. The weather was terrible on the trip. Could that have affected the ability of our ship to show up on the web site?

Thoughts?

[Paul Elliott]

Reliable AIS range is limited to line-of-sight, although in some unusual radio-propagation conditions the range can be hundreds of miles or more. Marinetraffic.com uses shore-based volunteer / hobbyist receivers so once you sail out of sight of land your signal will not usually be picked up or shown on the Marinetraffic website. Your own AIS receiver/transponder will still see other boats around you, and they will see you.

There is worldwide satellite-based AIS reception that you can access via a paid subscription at Marinetraffic.com, but the coverage for Class-B AIS is marginal -- perhaps one or two pings per day on the average, and often less.

[SteveInMD]

AIS was designed for electronic ship to ship collision avoidance communication on two VHF frequencies. It has no direct affiliation with MarineTraffic. MarineTraffic hopes that volunteers, mostly ham radio guys will collect the signals and send the data to their website. If you want to know if your AIS system is working you should be asking other vessels if they can see you on their AIS display, not people looking at MarineTraffic.

[dlymn]

A friend has AIS on his boat and like you his passage disappears quite often. It's hard to predict as it depends on so many factors such as nearby landbased receivers and others. Ship to ship should be Ok over less than 6 miles, but any boat under 300 tonnes is not required to use AIS. Very few sail and motor boats have it. For bluewater sailors it ight be a lifesaver, but for day cruisers, it's a cute accessory.