Question re: tracking boats at sea

[Steve_in_lex]

This isn't related to C-34s, but I'd appreciate any general knowledge about tracking boats far out to sea.  On Saturday (12/10) our daughter left the coast of Maine on a straight shot to Antigua aboard a 105' schooner, Eros.  Using Marine Traffic app I tracked Eros until she was about 25 miles off shore, traveling 9.5k due south; but I haven't been able to pick up any sightings since then.  I assume it's because they're out of range of land-based AIS antennas, but would have expected Marine Traffic to indicate a satellite-based position.  (MT shows the type of boat without identification for sat-based pickups, with an extra charge to identify it; but there's no sailing vessel in the area where they should be.)   Any suggestions on how to search for a satellite signal?  (I'm wondering if that requires a different type of AIS transmitter?). Thanks.

[Jim Fitch]

Hi Steve -

My understanding from tracking my son the same way, is that the AIS is just a radio signal and Marine Traffic is only going to show a location when your daughter has the radio on and it's in range of whatever tower Marine Traffic is pulling signals from.  Even when my son was in the ICW there were times when I didn't get a location for long periods.  When they'd head offshore there was nothing.

I don't know anything about a satellite version of Marine Traffic but the boat would have to be transmitting a signal that a satellite would pick up and you'd both have to subscribe to the service.  There are definitely satellite tracking services and transmitters available and the schooner may have one but I'm not sure that shows up on Marine Traffic.

Jim

[KeelsonGraham]

You have to pay to get the satellite tracking data on such websites.

[Kyle Ewing]

I don't believe you need special equipment for class B sotdma to be picked up by a satellite, however you have to enable "long range broadcast" in the settings menu.  Marine Traffic will show a ship with "position received by satellite" but no identifying information unless you pay.

This is based on experience.  After enabling the setting on my Emtrak I noticed an unidentified boat (position received by satellite) at a location where ground based received don't pick me up but I had cell coverage. I was the only vessel within sight and speed matched my speed.

[tvorgitch]

I paid for a Marine Traffic upgrade and I was surprised how many very large ships in visible range did not appear. We were only a few miles offshore and and had good cell reception. I would not trust it.

[Noah]

Tvorgitch—I am confused. Why did you pay for Marine Traffic upgrade? Were you just curious or trying to use it in place of an AIS receiver?

KYLE: I have an older EmTrak 100 B transceiver and I don't think it has that extended programmability. I have to check. Unfortunately, it is buried behind an instrument panel so not easy to reach inputs.

[tvorgitch]

Noah,

I got the starter subscription more out of curiosity but also as a test to see if it could work in place of an AIS receiver. I realize that the paid plan only offers more info and should not change what ships are seen. A friend from Portland was with me on a sail to Anacapa and she noticed some of the ships we could easily see did not appear on Marine Traffic. We thought it may have had to do with a weak cell signal, so we continued to check and still had issues as we approached the harbor.

[waughoo]

If you were offshore, it is possible that Marine traffic would not have those ships on their map.  The beauty of AIS is that it is line of site radio location.  Thus you will be able to see who is transmitting within your receiving circle.  Thus, HIGHLY relevent data.  If you were inland, marine traffic could be a suitable backup if your ais failed, but I would not want to rely on it as a primary system.

[Steve_in_lex]

Postscript:  The boat I was wanting to follow (between Maine and Antigua) arrived in Antigua just fine.

However, I poked around Marine Traffic and yes, but if you still can't see the vessel with the satellite upgrade, it may be that, "The vessel is equipped with a Class-B receiver, which is more difficult to be picked up by the satellite."   That might've been the issue.

https://help.marinetraffic.com/hc/en-us/articles/204809588-Activate-Undelayed-Satellite-AIS-tracking