AIS 'Scare'

[Playtime]

Had a bit of a scare yesterday evening when AIS (marinetraffic.com) reported my boat as leaving Port Solent around 6pm and exiting the harbour at 1921 while I was at home having dinner.

Earlier yesterday I had taken the boat on a day sail from Port Solent to Cowes and back, returning to the berth around 5pm and turning off all electrics including the AIS.

The new AIS reported passage seemed to be following my earlier route so I thought it might be spoofing or a software bug somewhere in the system. However, my wife was sufficiently concerned that the boat was being stolen that she persuaded me to drive to Port Solent (only 3 miles away, fortunately) and check that the boat was still there, which it was. Marinetraffic.com, though, was continuing to report it steaming west down the Solent!

Clearly there was a problem with marinetraffic.com reporting, so I wrote a quick email to them suggesting that someone was maybe spoofing the system and this is their reply -

"AIS is designed to be open and anyone could transmit any kind of data. Spoofing is easy.

However this is not the case for your vessel. The wrong data originated from a malfunctioning AIS receiver that contributes data to our system. It looks that it forwards the collected data with a delay of many hours. We have blocked this data feed and we will investigate it further.

Thank you for your feedback and please excuse us for the inconvenience caused."

Has anyone else had this sort of scare?

 

[laika]

Very valuable cautionary tale. Perhaps a link to playtime's post should be the standard response to anyone asking "Are these AIS phone apps nearly as good as the real thing?"

 

[sarabande]

does that mean your AIS is now blocked ? It's food for thought that they say anyone can spoof, say, a super fast ferry hammering through fo up the Solent.

Is Lenseman available for comment on this ?

 

[prv]

does that mean your AIS is now blocked ?

No - it's the receiver they blocked, not his transmitter. Presumably in such a busy area there will be plenty of other receivers to cover the loss.

It's food for thought that they say anyone can spoof, say, a super fast ferry hammering through fo up the Solent.

It shouldn't be that much of a surprise. It's basically just the digitally-signalled version of someone pressing transmit on their VHF and saying "I'm a super-fast ferry hammering up the Solent". Although in fact that would be much easier, as it would take a fair amount of technical skill to put together a home-made AIS transmitter that will broadcast whatever you tell it to. But the concept is simple enough.

Pete

 

[Sandyman]

Probably just a time delay fault on the Rx

 

[prv]

Probably just a time delay fault on the Rx

Errm, yes, that's exactly what they said in the original post

Pete

 

[laika]

it would take a fair amount of technical skill to put together a home-made AIS transmitter that will broadcast whatever you tell it to.

...but almost trivial* to send "made up" AIS sentences to marinetraffic's receiving ports after you've registered as a receiving station.

*For some definition of "trivial" which may be non-trivial for skilled radio engineers which would have no problem putting together the transmitter prv suggests...

 

[prv]

...but almost trivial* to send "made up" AIS sentences to marinetraffic's receiving ports after you've registered as a receiving station.

True, but hopefully nobody's using the Marine Traffic Internet service to avoid fast ferries in the Solent...


...are they? Oh no, of course they're not

Pete

 

[nigelmercier]

Perhaps a link to playtime's post should be the standard response to anyone asking "Are these AIS phone apps nearly as good as the real thing?"

Exactly, the apps are useless for navigation, merely toys.

And I'll say in advance that anyone who thinks otherwise is a muppet

 

[Playtime]

Marinetraffic.com is a useful site but certainly not to be used for real-time collision avoidance.

It is good for reviewing your track after a passage and also for keeping an eye on friends.

 

[Sandyman]

Errm, yes, that's exactly what they said in the original post

Pete

My error. Thanks for pointing it out. Very good of you.

 

[Ex-SolentBoy]

Exactly, the apps are useless for navigation, merely toys.

And I'll say in advance that anyone who thinks otherwise is a muppet

Yes, but using an AIS app for navigation is only slightly more stupid that using proper AIS for navigation. Both still rely on a delayed signal transmitted voluntarily by a portion of shipping.

 

[Bru]

Exactly, the apps are useless for navigation, merely toys.

And I'll say in advance that anyone who thinks otherwise is a muppet

Well, at the risk of being branded a muppet (it wouldn;t be the first time, my festival stage team nickname is, in fact, "Muppet"!) ...

I don't entirely agree with you there. Crossing the Harwich shipping lane, we have found the app to be useful to obtain a more detailed picture of the movements of vessels which we have spotted with the good old Mk.1 Eyeball

I would not want to rely on an AIS app in fog (for example)* of course but where I can positively relate what I can see from the deck to what is presented on the app it is a useful source of additional information

* Then again, I wouldn't want to rely on a full AIS receiver alone in fog, any and every source of information should ideally be verified and cross checked

 

[prv]

Both still rely on a delayed signal transmitted voluntarily by a portion of shipping.

Proper AIS shouldn't be delayed, unless you're referring to the milliseconds while the signal is processed and a gap is found for transmission.

Pete

 

[Ex-SolentBoy]

Proper AIS shouldn't be delayed, unless you're referring to the milliseconds while the signal is processed and a gap is found for transmission.

Pete

Badly stated by me. I meant the transmission isn't continuous, so the vessels aren't necessarily where you see them, just where they were when they last transmitted

 

[Bilgediver]

Yes, but using an AIS app for navigation is only slightly more stupid that using proper AIS for navigation. Both still rely on a delayed signal transmitted voluntarily by a portion of shipping.

Could you elaborate on this ? There might be an on off switch but I was not aware that ships could add a delay feature so they do not appear to be where they really are????

 

[prv]

Badly stated by me. I meant the transmission isn't continuous, so the vessels aren't necessarily where you see them, just where they were when they last transmitted

Yes, true. Though for class A, the maximum delay is ten seconds (travelling in a straight line at less than 14 knots), reducing to 2 seconds when going faster than that and changing course. Nobody should be cutting things so fine that a few seconds matter.

Obviously you may miss a few transmissions, increasing the inaccuracy of the information, but hopefully only at long range where it matters less.

Not that I'm suggesting people should sail about looking only at their AIS screen, of course.

Pete

 

[Giblets]

When I read the title of this thread I though for one brief moment that Fay's Fantasy had actually ventured outside Port Solent!

 

[sailorgirl]

Marinetraffic.com is a useful site but certainly not to be used for real-time collision avoidance.

It is good for reviewing your track after a passage and also for keeping an eye on friends.

Also useful for tracking a shipment if you know what ship it is on though it can be a bit bemusing - Dubai - Karachi- Mumbai - Mundra seems a bit round about way of getting to Tilbury and with the AIS signal is mostly off in this high piracy area when the ship is actually sailing we've no idea where its going to turn up next! But it is fun way to while away the days until we ship ourselves to Portsmouth...

 

[Playtime]

When I read the title of this thread I though for one brief moment that Fay's Fantasy had actually ventured outside Port Solent!

I use Fay's Fantasy to check my AIS receiver and plotter before I leave Port Solent. Good reliable signal, always there.