There is ADS B and ADS C. Most commercial
aircraft have upgraded to ADS C. For us, in the cockpit
it is seamless. It can use VHF
, HF and Sat. Domestically, it is likely using a ground station. (B) On the ocean or over the pole however, it would be using HF or Sat. The ADS simply sends out position reports and it can also be interrogated by the control agency. The communication side of things is called CPDLC, ( Controller Pilot Data Link Communications
. ) it will also use HF or Sat if needed. With CPDLC, we communicate with ATC via text messaging rather than voice.
I love the map used by the US. So typical, everything stops at the 49th.
Just as you said, an AIS
unit on a boat basically does the same thing as ADS but it's range is limited by line of sight from the VHF
antennae location. However, combine an AIS with a satellite based texting unit like the DeLorme InReach SE and for less than a 1000 bucks, you basically have the same suite we have in a 100 million dollar airplane!