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From: Dave Cooper (no email)
Date: Mon Jun 04 2007 - 09:52:11 EDT
This was posted on the PUP list and I thought it might be of interest here
also. AIS is a subject of great interest to both lists, IMHO.
Dave & Nancy
Swan Song
Roughwater 58
Caribbean Cruise '07
787 990-6064 Sat
954 252-3830 fax
<John "Seahorse" wrote: A glance at the AIS display (on CE) showed the
triangle symbol facing the wrong way! Further investigation showed that all
the data was correct, including course, but his heading was fixed at 17
degrees! So we learned something today,>
I have reported on this before. If we look at the list of boats that show up
on our AIS window on Coastal Explorer we can always find one or more whose
data is not correct. Most are operator input errors but some are caused by
the installation or equipment failures that are not noticed by the operator.
There are several boats that have a 180 degree error in their heading
information. I have spoken to them about it but they don't seem to either
care or get it fixed. Hmmmmm, this would tend to imply that there is no
enforcement of the integrity of the AIS system. I know that the Coast Guard
doesn't check this as part of their "boarding and safety checks of vessels
as they boarded one of the ships, Sea Searcher, that has an 180 error last
week off St Thomas and it still has the same error. So I guess I would ask
the question: Who has responsibility for the enforcement of the AIS data
integrity/stream?
There doesn't seem to be any kind of "self test" of the data that is
actually being transmitted and thereby received by other vessels. One needs
a hand held or portable AIS receiver to perform this function. At the moment
I know of no commercially available unit but it wouldn't be hard to make up
one that would plug into a laptop.....in fact I have an extra SR161 that I
think we can do this with. Pretty limited use tool but it could be
invaluable.
In talking with a couple of installers of Class A AIS gear they have nothing
other than asking other ships for a report on the data they receive.
So once again as John has confirmed AIS is a great aid but like any other
aids to navigation it needs to be confirmed with other forms of input,
visual, radar, communication, etc.
As always YMMV
Cheers
Dave & Nancy
Swan Song
Roughwater 58
Caribbean Cruise '07
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