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AIS in use at sea


Island Time

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Hi, I was thinking about some of the questions I've had about AIS. So I've written a bit about our experiences, what AIS is, How it works, and what it gives you. Here is a link;

http://www.neptunes-gear.com/pages/ais

 

If you don't want to read that, you might be interested in this screen-shot from our AIS near Singapore;

 

Ais Screenshot.jpg

 

Just for those who think they can always tell when a ship poses a danger!

 

Matt

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I'm also a fan of AIS for coastal / offshore cruising.

 

The big caveat is that AIS is NOT a replacement for maintaining an active watch. Many boats dont have it, and many boats that have it, dont have it on.

 

Another factor is that your position broadcast is 'public'.

 

Of course this means that motivated pirates, ex-wives, and Search & Rescue co-ordinators can see if your location is of any interest.

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Agreed. However most AIS units can disable transmit if you want, so they turn into receive only. Alone, and AIS is NOT a watch system, just an Aid. It is also NOT, as some people have suggested, a replacement for Radar. Radar tells you what it there, including land etc. AIS tells you what other AIS equipped boats are nearby. That is an enormous difference!

 

AIS is at it's best in busy waters, or crossing oceans.

 

The list of targets can often/usually be filtered, for example

what vessels pose the greatest/most imminent threat etc...

 

Matt

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I always say it but be aware that sometimes the AIS position broadcast by a vessel is wrong, can be out by miles, and that goes for Class A units as well.

 

http://www.furuno.co.jp/en/news/notice/ ... 4_001.html

 

Quite old but still relevant:

http://www.navcen.uscg.gov/pdf/AIS/USCG ... re_AIS.pdf

There are more Furuno units with the issue than listed.

The manually entered offset mentioned includes when the GPS is set to a datum other than WGS-84.

 

Occasionally plot the position that your AIS unit transmits - that will show if it is affected.

 

 

AIS - a great aid to safety of navigation - learn it's limitations, learn it's limits on your boat.

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Again Rigger, Agreed. Every device has it's limitations. Check your AIS with Radar/Known object positions. Make sure YOUR unit is programmed correctly!

Even a paper chart can be wrong, so can ANY plotted position, electronic or otherwise. In my experience, AIS positions are more likely to be right than your transit or sextant position! Yes there are errors, but they are rare.

 

The is NO substitute for the mark one eyeball. If you can see a freighter dead ahead, dead ahead it is! Be careful, check everything with more than one data source! This is basic seamanship.

 

Matt

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The skipper has just fitted an AIS system on the boat I sail on. It was quite good during the coastal as a number of boats around us had it fitted. Whist we were keeping an active watch it was also good in the dark to see what headings and boat speed the boats around us were achieving so we were able to gauge our performance - sometimes good :D and sometimes bad :(

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Considering the way they light ships from stem to stern with piddly little nav lights hidden in the general glow , AIS is nice just to get the heading as well as all the other stuff. Plus it makes for conversation with all the destination . We came into Moreton bay on monday evening and had one ship offshore " not under command",... that made for a bit of speculation. And it was really nice to have the heading of some trader when we were making for the first leading light at the channel. It was just a ball of light and really hard to get a bearing on due to the sea state. No problemo of course, but very nice to have it ( AIS) in the quiver.

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