marinetraffic.com is great, but I would not rely on it for navigation. marinetraffic.com relies on volunteers for for their receiving stations. And ... as they state on their site, the data can be up to an hour old. As I interpret that, there is no guarantee vessels reporting AIS are actually where they appear to be at any point in time.
As to actual use of AIS, I find it a great additional source of information. Just one more tool to aid in navigation. Is it right for everyone, or in all cases, based on the responses here, no. But, I am firmly in the "I like it" camp.
We were headed south from Salt Spring Island in dense fog. AIS allows the chartplotter to track the courses of the ferries and other commercial vessels easily. We could "see" the ferries coming through Active Passage and leaving Swartz Bay before we could see them on radar. The chartplotter displayed names of the vessels and speeds as well as plotting their course and reporting how close we would pass each other based on current course and speed. Radar showed us all the other boats, but not with this level of information.
We left Friday Harbor headed for Port Townsend. It was a beautiful clear day. The closer we got to Port Townsend, the foggier it got. By the time we were approaching the traffic lanes, I could barely see the bow. AIS allows us to see the commercial traffic in the area and stay out of the way. Just to be sure and mention it, we also contact Vessel Traffic to be sure everyone knows we are there and what we are doing when we around the traffic lanes in reduced visibility.
When we are crossing the Puget Sound traffic lanes on the way back to the locks, we can easily determine the speed and distance of all commercial traffic near us. This makes it easier for us to be sure we cross easily and stay out of the way of everybody else. AIS just adds more information and allows us to make more informed decisions.
We originally installed a
Comar AIS receiver but replaced it with an Garmin AIS transponder (when we got a good deal). I figure if we are going to benefit from receiving AIS information, we might as well go ahead and transmit too.