T&T: AIS and Passage from Hong Kong

[Mike Maurice]

We had a Furuno FA-100? model on the last trip. It was connected to the 
Nobeltec Chartplotter. The alarm was set for 1 mile CPA(Closest Point of 
Approach) at 12 minutes from CPA.
About 10% of the AIS targets had garbled data which was partially but 
not completely useless.
We were told by the Canadians that our unit was sending garbled data.
About 20% of the AIS targets set off our CPA alarm.
1 AIS vessel approaching from astern came within 1/4 mile at night in a 
dense traffic area. They were never a threat, but when about 1/2 mile 
behind, I slowed down and allowed them to pass as they were only doing 
about 1/2 knot faster than us and I wanted to shorten the time we would 
be nearby and in front of them.
On some occasions in warm water areas we had targets start showing at 96 
miles, this was the exception. In most cases 30 miles was the maximum.
 From Hong Kong to South Korea we often had 10-20 AIS targets at all times.
In almost 7500 miles we only had to make an extreme course change once 
or twice with a nearby AIS target.
American ships appear to be monitoring channel 13 even in the open ocean.
At about mile 7000 we encountered a sailboat under sail, 2000 miles out 
of Hawaii. They did not have AIS. The ARPA system predicted a close 
quarters situation of about 30 feet, we slowed down to a crawl and 
passed behind their stern at about 100 yards, in calm seas and clear 
visibility. At one mile I called them on 16 and notified them of our 
intentions. They were preparing to get nervous. Do not underestimate the 
power of random chance bringing 2 vessels to a collision in the open 
ocean, with no design on the part of either operator.

AIS at 2.5 watts being broadcast from a sail or other boat is an 
excellent way to avoid being run down.

Even if you do not have chartplotting of the AIS targets, the AIS unit 
will alarm if you set up a CPA and time.

Mike
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Capt. Mike Maurice
Beaverton Oregon(Near Portland)