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Old 01-11-2016, 14:04   #1
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New AIS Overview

While most of the AIS is transparent to the user, there has been a lot of development behind the scenes. The IALA (International Association of Lighthouse Authorities) has issued a revised AIS overview document

http://www.navcen.uscg.gov/pdf/IALA_...iew_of_AIS.pdf

If you use AIS, or are planning to buy an AIS for your boat, this is a long, but very worthwile summary of the technical aspects.

Here are a few of the things I learned:

1. The use of AIS is expanding from collision avoidance to surveillance and search and rescue.

2. There are AIS repeaters which can extend the range of all AIS stations.

3. There are AIS satellite receivers which cover the open oceans. Because these satellites can hear so many stations, they can be overwhelmed, so Class A stations are going to transmit special messages for the satellites.

4. There is a new type of Class B station under development, with both higher and lower transmit power levels.

5. There are now MOB AIS transmitters and EBIRB AIS transmitters which transmit normal Class A position reports, with messages like "MOB active" and "EPIRB test". I'm not sure that older AIS software would display them correctly.

6. Class B position and static messages have different Messages ID's than Class A, so it would be easy to suppress them.

7. There are 'ghost' AIS targets, both intentional and unintentional. Some of the unintentional ones are due to multi-path interference in the GPS signals.

8. The government agencies can query your AIS for more information and tell it to shut up or to change frequencies.
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Old 02-11-2016, 07:31   #2
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Re: New AIS Overview

I'm glad I got my AIS when I did. Still, it's hard not to worry about all our hardware becoming obsolete. It's bad enough that a $600 cell phone is obsolete in two years. The day a $5000 electronics package becomes obsolete in two years, I give up.

And the worst part is, the manufacturers don't provide software upgrades for models that are just a year or two old.
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Old 05-11-2016, 06:00   #3
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Re: New AIS Overview

Another recent development in use of the automatic identification system (AIS) has been to create electronic-only aids to navigation (AtoNs) called AIS AtoNs. In the USA the Coast Guard has been deploying AIS AtoNs, and now at least one private entity has been authorized to deploy private AIS AtoNs. For more on this new application of AIS technology, see my article on this subject at

PRIVATE AIS VIRTUAL AIDS TO NAVIGATION
Private AIS Virtual Aids to Navigation - CONTINUOUSWAVE
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Old 05-11-2016, 06:32   #4
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Re: New AIS Overview

Quote:
Originally Posted by CaptTom View Post
I'm glad I got my AIS when I did. Still, it's hard not to worry about all our hardware becoming obsolete. It's bad enough that a $600 cell phone is obsolete in two years. The day a $5000 electronics package becomes obsolete in two years, I give up.

And the worst part is, the manufacturers don't provide software upgrades for models that are just a year or two old.
Nothing in the document implies current Class B CS is becoming "obsolete".....???
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Old 05-11-2016, 07:13   #5
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Re: New AIS Overview

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Nothing in the document implies current Class B CS is becoming "obsolete".....???
The way I read it, new features that the existing hardware doesn't support, such as the last 5 points in the original post, seem to imply that my hardware and software will not work correctly in the future. And since many manufacturers refuse to update the software for their two-year-old hardware, it seems that some obsolescence is possible. I hope I'm wrong, but I think it's a legitimate concern.
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Old 05-11-2016, 11:02   #6
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Re: New AIS Overview

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Originally Posted by CaptTom View Post
The way I read it, new features that the existing hardware doesn't support, such as the last 5 points in the original post, seem to imply that my hardware and software will not work correctly in the future. And since many manufacturers refuse to update the software for their two-year-old hardware, it seems that some obsolescence is possible. I hope I'm wrong, but I think it's a legitimate concern.
They are specifying new functionality for "Class B". That does not mean the existing Class B will no longer work, it means when you buy the new "Class B" when available, it will have the new functionality. As far as manufacturers offering the new functions in the older units, I'm sure there is as much marketing involved in the decision as well as engineering. I certainly doubt they could increase output power in an existing unit from 2 watts to 12 watts. And they may or may not be able to add the new data structures. As far as the display showing MOB AIS as a boat, that's a display problem, your current AIS unit will certainly receive the broadcasts, so it's whatever you are displaying on needs updated.
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Old 05-11-2016, 16:59   #7
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Re: New AIS Overview

Yes, I think the only thing in that list (and the summary document) that isn't in all products sold today is the Class B/SO. I don't know of any devices that meet the SO spec - at least not yet.

MOB, querying and commanding AIS devices, and different Class B sentences have been around for a long time. If you think you really want a Class B/SO device, then by all means wait, but otherwise a Class A device is a Class A device and meets the spec. Same for a Class B device.
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Old 15-11-2016, 15:32   #8
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Re: New AIS Overview

Very helpful documents. Thanks for sharing
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