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Old 16-06-2019, 13:22   #1
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What’s Going on with this AIS Target?

Notice the ‘heading’ field. Anyone know what’s going on here?

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Old 16-06-2019, 13:56   #2
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Re: What’s Going on with this AIS Target?

Its going to another dimension LOL
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Old 16-06-2019, 16:22   #3
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Re: What’s Going on with this AIS Target?

Maybe an artifact of the lack of boat dimensions?
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Old 16-06-2019, 17:45   #4
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Re: What’s Going on with this AIS Target?

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Notice the ‘heading’ field. Anyone know what’s going on here?

Attachment 194023
Is the Lat and Long correct?
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Old 16-06-2019, 18:45   #5
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Re: What’s Going on with this AIS Target?

Class b doesn’t transmit heading. So something is weird. Maybe on your end.
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Old 16-06-2019, 20:16   #6
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What’s Going on with this AIS Target?

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Class b doesn’t transmit heading. So something is weird. Maybe on your end.


Yea possibly. I’m not too bothered, I just thought it was kind of cool. Even though it was only 2.5 miles away and visibility was great I couldn’t see it, so it’s presumably some kind of beacon.......... but then it’s also moving at 10 knots?! Who knows. There’s a lot of weird-looking stuff out there.

I was chatting to one of the conservation officers on St. Helena a couple of months ago. They told us about a long-liner that they were tracking on radar whose course was really erratic. They tracked it for a while and an image emerged - the coast of China. They’d set their AIS to be offset by x thousand miles and then fished illegally in the middle of the South Atlantic......... appearing according to AIS to be just off the coast of China.

We saw similar stuff in Indonesia; you get a target on AIS and the CPA is 8,000 miles.
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Old 16-06-2019, 20:22   #7
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Re: What’s Going on with this AIS Target?

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Originally Posted by smac999 View Post
Class b doesn’t transmit heading. So something is weird. Maybe on your end.
Class B messages include heading.
https://www.navcen.uscg.gov/?pageName=AISMessagesB
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Old 16-06-2019, 20:51   #8
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Re: What’s Going on with this AIS Target?

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Class b doesn’t transmit heading. So something is weird. Maybe on your end.
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Class B messages include heading.
https://www.navcen.uscg.gov/?pageName=AISMessagesB
The correct statement should read "most Class B don't transmit HDG".....

Although the data output format supports heading information in "some" Class B units, in general units are not interfaced to a compass so this data is seldom transmitted.....

If a vessel is required to carry a Class A then it is required to be interfaced with a compass feed, there is no such requirement for Class B.....

Without a compass interface the Class B cannot transmit a Heading, True or otherwise.....
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Old 17-06-2019, 00:49   #9
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Re: What’s Going on with this AIS Target?

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The correct statement should read "most Class B don't transmit HDG".....

Although the data output format supports heading information in "some" Class B units, in general units are not interfaced to a compass so this data is seldom transmitted.....

If a vessel is required to carry a Class A then it is required to be interfaced with a compass feed, there is no such requirement for Class B.....

Without a compass interface the Class B cannot transmit a Heading, True or otherwise.....
That's probably true with older installs. With more boats using nmea 2000 buses it should be less so. My older Emtrak AIS support 2000. So heading comes from the Autopilot compass that is on the bus.
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Old 17-06-2019, 01:11   #10
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Re: What’s Going on with this AIS Target?

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That's probably true with older installs. With more boats using nmea 2000 buses it should be less so. My older Emtrak AIS support 2000. So heading comes from the Autopilot compass that is on the bus.
I wasn't referring to either old or new, NMEA O183 or 2000, i was referring to the owners not interfacing a compass, the vast majority still don't no matter the capability of there particular unit......
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Old 17-06-2019, 01:29   #11
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Re: What’s Going on with this AIS Target?

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I wasn't referring to either old or new, NMEA O183 or 2000, i was referring to the owners not interfacing a compass, the vast majority still don't no matter the capability of there particular unit......
Understood, my point was if you plug into the 2k bus then heading just comes along with it without doing any interfacing, assuming you have a compass on the bus for an AP
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Old 17-06-2019, 01:32   #12
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Re: What’s Going on with this AIS Target?

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Understood, my point was if you plug into the 2k bus then heading just comes along with it without doing any interfacing, assuming you have a compass on the bus for an AP
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Old 17-06-2019, 02:46   #13
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Re: What’s Going on with this AIS Target?

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Notice the ‘heading’ field. Anyone know what’s going on here?

Attachment 194023


Weird stuff like this aside, are you happy with your Matsutec AIS? I’ve fitted one but have had no chance to test it yet.
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Old 17-06-2019, 04:30   #14
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Re: What’s Going on with this AIS Target?

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Weird stuff like this aside, are you happy with your Matsutec AIS? I’ve fitted one but have had no chance to test it yet.


Yes, very. For the price, functionality, and convenience of being able to program your own MMSI into it it’s great. We only bought ours to satisfy an Indonesian requirement that ‘all foreign vessels must be equipped with an AIS transponder’ but we’ve come to really love it. Only downside is that the CPA alarm doesn’t work. Not a problem for us because we have a separate receiver on which it does work, but if yours is the same and it’s the only AIS you have it could be a major disappointment. I’d read some reviews before I bought it which said similar things. Fingers crossed yours works OK.
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Old 17-06-2019, 05:12   #15
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Re: What’s Going on with this AIS Target?

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Only downside is that the CPA alarm doesn’t work. Not a problem for us because we have a separate receiver on which it does work, but if yours is the same and it’s the only AIS you have it could be a major disappointment. I’d read some reviews before I bought it which said similar things. Fingers crossed yours works OK.
That's a worry. I had not read of that particular problem....

I think my CPA alarm is working from my testing in the marina, but I will find out more. Thank you for the heads up.
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