Where we sail AIS is a nice adjunct to radar
but not to be depended upon in fog
as your sole source of information.
A few year ago Tim R. and I (Tim is another forum member
here) were in the thick Maine
pea-soup (maybe 100 feet of vis) when I saw an AIS target on the plotter. I had already also noted my radar
giving a return that looked almost as echos being repeated after the main target. They were good strong targets just oddly spread......
I knew my radar
was well tuned, and not lying, so I picked up the VHF
and hailed the AIS target, this is a beautiful benefit of AIS. Sure enough it was a tug towing two barges with 900 feet of cable between each barge. We were in a crossing situation!
If going by only AIS we could have been really dumb & split between the tug and barges in tow not having a clue they were even there.. The barges in tow were not displaying AIS signals, nor was there any data to tell us the target was towing a barge let alone two at 1800'. The AIS only identified the tug by name, speed etc....... Using AIS only could have been a death sentence or dismasting
in that situation....
It was radar that alerted us to the actual positions of all three targets
. AIS allowed us to hail the tug easily and confirm what the radar was showing, but alone AIS could have been very, very dangerous in that foggy crossing situation.
Both tools work really well together
but if I must have only one device I will take my radar every day of the week for sailing in Maine
and the Maritimes. Blind trust of AIS, in the fog
, is just not a very good idea. I won't even go into slow updates & fast moving vessels, in the fog, on AIS....
For me AIS is a great complimentary tool
to radar not
a primary tool...