Originally Posted by conachair
Originally Posted by steve77
From my reading on the internet, there are several firms that operate satellites capable of receiving AIS signals, both Class A and Class B. They take care to point out that class B signals may not always be received due to the lower signal strength and less frequent transmission.
However, these companies do not offer this information to the general public for free. They offer paid subscriptions to allow shipping companies and other interested parties to track their vessels.
The free AIS tracking services appear to all be from terrestrial stations.
Am I mistaken?
Pretty sure that's it. And just noticed it's already been mentioned by Paul Elliot
Yes, we're all three of us correct!
I was probably unclear in my post though -- as you guys say, the satellites are receiving the VHF AIS transmissions from vessels on the high seas.
Yes, there are numerous satellite-based tracking services that use direct-to-satellite transmitters on the boats (Spot, Yellowbrick, InReach, and others), but the AIS VHF reception
by satellite is a fairly new thing. There have been experiments with this for several years, and it has recently gotten good enough that it is now being done commercially. Pretty amazing, really!