[PUP] AIS pitfalls

[Dave Cooper]

John wrote: To your point, the other 'fun' thing about depending too much on
AIS is to make sure you can separate tugs from tows.>

I can't agree with you more. I come from the days of compass, lead line and
some hand me down charts with notes scribbled all over them.

I was the master of the Nina, a replica of Columbus' 15th century caravel.
We tried to use less than modern techniques to find our way around. We made
it from San Juan, PR to New York without any outside aids including a modern
day Sextant so I am aware of the "old ways" and the needs of the modern day
mariner.

AIS has a one of its many ship types is 31 for towing and 32 for a long tow
so again if the operator of the AIS is on the ball then he will have punched
in the correct code for the tow. This is sort of like navigation lights. A
long tow is a different configuration than a short tow which is different
that no tow. So if the master of the vessel is responsible for the proper
light configuration why the "h..." aren't they responsible for their AIS
data.

Just seems that the light configuration part of a master test is front and
center to pass. Has anybody seen the same emphasis on the proper AIS
configurations? Again AIS is a mandatory requirement...we're not talking
about optional compliance.

I sure hope compliance is bubbled up to the top layer before there is an AIS
related accident. It has great promise to help everyone as the seas become
more crowded and good clear information is available to plan a course thru
heavy traffic zones. Transponders have been on planes since the late 50's.
They slowly tricked down to a wider variety of aircraft. Today if you are
IFR and turn off the transponder you might find a note from the FAA in your
mailbox. Better yet try an approach from an offshore location entering say
the east coast of the US without squawking the correct code and not filing
48 hours in advance your entry. You might find an F whatever off your wing.
Not so with AIS...yet.

This is also when the presentation of the data becomes so important. If the
sender is generating the correct codes then the receiver gets them and
passes them down the line to the.......SOFTWARE......Uh oh programmers
who've never been to see are going to present me with information at sea to
tell me what I "see". Sounds like an opportunity here for good stuff or
disaster!
Like how about a "towing symbol for a type 31 and a longer one for a type 32
or a color change or a boat with a trailing boat. I think you see what I'm
trying to say. The data is packed with all of this info and to just show a
stupid triangle when you have the richness of the types available means
they....the programmers....just don't get it, IMHO.

I know that Rose Point is planning a new version that will be available
sometime later this year. I sure hope that they spend some time on the
expansion of the simple data that they now display so we can get some
differentiation between those ship types, better user filtering, better use
of alarms along with more information present for the data stream. Lots of
room here.

Hey, I can't afford to have a copy of everyone's plotter/nav software so
maybe there is already someone out there that does all this. If so I missed
the announcement and the demo version so please let me know so I can look at
it when I get a moment.

As always YMMV...
Cheers

Dave & Nancy
Swan Song
Roughwater 58
Caribbean Cruise '07
787 990-6064 Sat
954 252-3830 fax


-----Original Message-----
From: passagemaking-under-power-bounces@lists.samurai.com
[mailto:passagemaking-under-power-bounces@lists.samurai.com] On Behalf Of
John Marshall
Sent: Monday, June 04, 2007 2:51 PM
To: Passagemaking Under Power List
Subject: Re: [PUP] AIS pitfalls

To your point, the other 'fun' thing about depending too much on AIS
is to make sure you can separate tugs from tows. AIS gives you a
great position report on tugs, but the tow could be 600' or so
behind. I've talked to people who are into fine tuning their passing
in crowded areas by nit-picking the AIS CPA report and passing too
closely in fog. If you can see, the passing requirements for tug and
tow are obvious, as is the radar return. But watching only that
'omnipotent' AIS triangle and not paying attention to other
indicators (eyes, radar, common sense) is a recipe for disaster.

And not only for us little guys... an Ohio class nuclear submarine (a
Boomer) last year snagged a tow line with its sail while submerged in
the Straits of Juan de Fuca (we could see it from our house when it
surfaced) while trying to pass between tug and tow. Sub turned around
and went back to Bangor for repairs. Not an AIS issue (he was
submerged), but an object lesson that even the First Team can make
mistakes by relying too much on single instruments (in his case,
probably his passive sonar that could hear tug but not tow).

John Marshall
N5520 - Serendipity

On Jun 4, 2007, at 11:07 AM, Dave Cooper wrote:

> <Ron wrote: The USCG announced that the Navy in our area of North
> Carolina
> would be conducting tests that would disrupt both GPS and AIS. The
> latter
> would have to be a discrete frequency interference to avoid disrupting
> normal VHF safety communications.>
>
> Thanks Ron, this further confirms the point of pitfalls.
> However the AIS transponder will receive the false or modified GPS
> signal so
> it will give bogus location, course and speed data.
> The heading and other data is independent of the GPS so they would
> show
> normally.
>
> If the data is scrambled then they are using a VHF frequency
> transmitter and
> the VHF transmission would be affected...I doubt that this is what
> they are
> doing. If just the GPS data is affected then it's the satellite
> signal that
> they're messing with. A more likely scenario.
>
> This illustrates a bit more of what I've been trying to get across
> in my
> poorly worded rants here. The blending of these technologies, some
> old some
> new, into a yet newer package makes it hard for a lay person to
> understand
> who's on first. It looks like it also makes it hard for an AIS
> knowledgeable
> person to figure it out also.
>
> If you jam or spoof the GPS signal the whole of AIS in the area of
> the false
> signal is worthless along with all the other 7 GPS's we have doing
> whatever
> they do. If you jam the VHF AIS frequency only you only affect the
> AIS and
> nothing else. A doubtful exercise, IMHO.
>
> I guess the tows in this area will even be more confusing with their
> projected lines, symbols and location. Better get Penny and John
> down there
> to direct traffic ;-)
>
> As always YMMV....
>
> Cheers
>
> Dave & Nancy
> Swan Song
> Roughwater 58
> Caribbean Cruise '07
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