Ahoy,
I just looked on:
http://www.marinetraffic.com/ais/default.aspx?level0=100
On the web site I saw only three symbols pointing north and when I checked
their data they were steaming within a few degrees of north. Perhaps my
problem is with my own equipment. I went to Furuno's web site and asked
them about it but I have not heard a reply yet.
Targets on the web site with speeds of zero or .1 Kt showed a square symbol.
The AIS system does include data showing which way the vessel is pointing
even though the speed is zero. While GPS heading data is impossible (with
the rare exception of two-antenna units) if the vessel is not moving,
electronic compasses are common aboard vessels used with autopilots and
other nav station gear. They produce heading data at all speeds.
It has been some months since I was truly underway with traffic and I cannot
recall if stationary targets were shown pointing north.
But I do recall vividly that about half of the moving vessels are shown
pointing north on my screen whilst they are actually moving in some other
direction according to the vessel's AIS data window.
This was brought home to me off Cape Fear one dark night the first trip I
had the AIS. A motorboat approached on my port quarter whose AIS pointed
north (I was heading north), but he was actually steaming northeast. I had
a true picture on my radar and did contact him via VHF but even so the
passing was too close for my comfort.
The AIS symbol pointing north was a confusing input, and the fact that he
didn't seem to understand he was the give-way vessel.
It would be a Good Thing for the AIS triangle to always be pointing in the
direction of the target's heading whenever moving and a different symbol
used for a stopped (or almost stopped) target.
Norm
S/V Bandersnatch
Lying Julington Creek FL
30 23.8N 081 25.7W
-----Original Message-----
From: Craig
Sent: Wednesday, July 04, 2012 11:11 AM
To: liveaboard@liveaboardonline.com
Subject: Re: [Liveaboard] AIS Question
Hi Norm,
A thought: Are the vessels with the triangle pointing north moving? On my
landlubber systems if the object is not moving the system is unable to
determine which way it's pointing and the triangle goes to its default
position
Craig Scott AE6E
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