Navy and AIS

[NotBirdseye]

They Navy can quite easily jam any electronic communications over an area. One way they can do this is to flood receivers with garbage, sometimes this is actually unintentional as broadcasting a lot of data that may cross into unusual frequencies is not uncommon (in the IT world it's called: Denial of Service). They can either target the local area or they can aim for the satellites. Electronic warfare is something that most militaries are working on

Whether this was the problem... is hard to say. I'm pretty sure the military tend to avoid causing such issues (JSP 489 maybe or JSP 830?) rule #1 is generally: Don't P*** O** the civilians.

 

[NormanS]

They Navy can quite easily jam any electronic communications over an area. One way they can do this is to flood receivers with garbage, sometimes this is actually unintentional as broadcasting a lot of data that may cross into unusual frequencies is not uncommon (in the IT world it's called: Denial of Service). They can either target the local area or they can aim for the satellites. Electronic warfare is something that most militaries are working on

Whether this was the problem... is hard to say. I'm pretty sure the military tend to avoid causing such issues (JSP 489 maybe or JSP 830?) rule #1 is generally: Don't P*** O** the civilians.

Well, that doesn't stop them jamming GPS over quite large areas of the West Coast of Scotland, during "Joint Warrior" fun and games. And yes, it does p*** off the civilians.

 

[MM5AHO]

Someone asked if VHF can be affected by fog. It can. VHF is affected by the signal being refracted in different densities of air. That's what causes log range reception at times (tropospheric propagation). There's also ducting at sea level also caused by ducts of different densities of air. I once did some experiments on this across the Moray Firth. But it takes significant fog to make a difference noticeable on marine VHF with relatively unsophisticated signal strength measurements.
On AIS signals. Of course the transmitted position of a transmitting entity does not have to be the GPS position of the transmitter. Some lighthouses and buoys now have AIS, and the signal doesn't come from there it is transmitted from nearby ashore, but giving the position as where the mark is located.
I suspect some fishing boats do this same technique illegally. I once encountered a group of vessels off the south end of Arran, all showing on AIS, but when I got there, none seen visually. There were not there, and I don't know where they were other than showing on my chart plotter.

 

[Kukri]

On AIS signals. Of course the transmitted position of a transmitting entity does not have to be the GPS position of the transmitter. Some lighthouses and buoys now have AIS, and the signal doesn't come from there it is transmitted from nearby ashore, but giving the position as where the mark is located.
I suspect some fishing boats do this same technique illegally. I once encountered a group of vessels off the south end of Arran, all showing on AIS, but when I got there, none seen visually. There were not there, and I don't know where they were other than showing on my chart plotter.

I did not know that. I quite like the idea of telling a bunch of pirates that we are a few miles over the horizon.

 

[Old Bumbulum]

Following a career in aviation I don't believe for a second that GPS can be affected by fog. We know nothing of this as a GPS error and if it did exist we most certainly would for reasons too obvioys to mention.
Forget it, This is a complete myth.
Ducting is caused by diffraction effects at angles parallel or nearly parallel to the earth's surface. The vast majority of GPS signals arrive from far more acute angles where ducting isn't possible. It isn't a factor.

As that stuff about fishing boats masking their positions 'illegally"...I thought telling utter porkies was illegal? As well as being so utterly ridiculous as in this case - what;s next? UFOs being employed to mask crab-poachers?

I checked the date and Apr 1 is not for several months yet...

 

[westhinder]

Following a career in aviation I don't believe for a second that GPS can be affected by fog. We know nothing of this as a GPS error and if it did exist we most certainly would for reasons too obvioys to mention.
Forget it, This is a complete myth.
Ducting is caused by diffraction effects at angles parallel or nearly parallel to the earth's surface. The vast majority of GPS signals arrive from far more acute angles where ducting isn't possible. It isn't a factor.

As that stuff about fishing boats masking their positions 'illegally"...I thought telling utter porkies was illegal? As well as being so utterly ridiculous as in this case - what;s next? UFOs being employed to mask crab-poachers?

I checked the date and Apr 1 is not for several months yet...

I did not think anyone suggested GPS signals being affected by fog, but VHF and thus also AIS transmissions.
As the OP, I had the clear impression that someone was playing games with the AIS signals that day. Next to no ships were visible on AIS, although some were on radar. We did see a number of NATO warships that day, including an aircraft carrier and we heard a couple of warnings on the VHF about firing live ammunition, so there was clearly something happening around us.
Frankly I would be rather surprised if navies did not have a means of jamming AIS. Technically that can’t be too difficult.

 

[Roberto]

As that stuff about fishing boats masking their positions 'illegally"...I thought telling utter porkies was illegal?

.

They are not "masking their position", they send AIS messages with hand input position coordinates which are away from their real position.
It is a ascertained fact in many countries, possibly only outside the UK where I understand "telling lies" brings immediate vows for bringing back death penalty, or end up in Daily Mail front pages.

 

[prv]

They are not "masking their position", they send AIS messages with hand input position coordinates which are away from their real position.

I wonder what equipment they would use to do that.

Yes, clearly there's nothing in the protocol to prevent a station broadcasting whatever position it likes, but in practice to do it you're going to need a transmitter that accepts manual input for position. The only equipment I've come across with that facility was fairly large and rather expensive, designed to be rack-mounted in the shoreside equipment room of a VTS station or similar establishment. Units intended to fit on vessels have no legitimate use for broadcasting anything but their own present position, so I wouldn't expect any mainstream manufacturer to support it.

Is there some SDR system that's been packaged up in a way that your average fisherman can operate it? Dubious Chinese unit with a nonsensical combination of features? Something else?

Pete

 

[PilotWolf]

I wonder what equipment they would use to do that.

Yes, clearly there's nothing in the protocol to prevent a station broadcasting whatever position it likes, but in practice to do it you're going to need a transmitter that accepts manual input for position. The only equipment I've come across with that facility was fairly large and rather expensive, designed to be rack-mounted in the shoreside equipment room of a VTS station or similar establishment. Units intended to fit on vessels have no legitimate use for broadcasting anything but their own present position, so I wouldn't expect any mainstream manufacturer to support it.

Is there some SDR system that's been packaged up in a way that your average fisherman can operate it? Dubious Chinese unit with a nonsensical combination of features? Something else?

Pete

I would imagine that the GPS is external and being send in demo/training mode so you could put any position in you wanted to end to the AIS.


W.

 

[Roberto]

I wonder what equipment they would use to do that.

Yes, clearly there's nothing in the protocol to prevent a station broadcasting whatever position it likes, but in practice to do it you're going to need a transmitter that accepts manual input for position. The only equipment I've come across with that facility was fairly large and rather expensive, designed to be rack-mounted in the shoreside equipment room of a VTS station or similar establishment. Units intended to fit on vessels have no legitimate use for broadcasting anything but their own present position, so I wouldn't expect any mainstream manufacturer to support it.

Is there some SDR system that's been packaged up in a way that your average fisherman can operate it? Dubious Chinese unit with a nonsensical combination of features? Something else?

Pete

Hello Pete,
technically, I have no idea.
The subject was aired at a few meetings between maritime operators/authorities, among the examples were the MRCC tried and contact by DSC a fishing boat in a rescue area but eventually they found there was no one; a high speed ferry diverted its course to avoid a fishing boat but found no one, etc.
I do not know the exact circumstances, but that seems to happen often enough to begin causing some concern. There was also an article in the SNSM (like RNLI) magazine, I ll look for it.
Myself have only had fishing boats suddenly "appear" on AIS, but that of course was simply they being in stealth mode for some time.

regards
r

 

[SimonFa]

They Navy can quite easily jam any electronic communications over an area. One way they can do this is to flood receivers with garbage, sometimes this is actually unintentional as broadcasting a lot of data that may cross into unusual frequencies is not uncommon (in the IT world it's called: Denial of Service). They can either target the local area or they can aim for the satellites. Electronic warfare is something that most militaries are working on.

I spent 4 years in Germany working on jammers and intercept equipment, which was interrupted by the Falklands war when we took down some jammers and used them in the real world.

There's nothing special about jamming, all you need is a transmitter on the same frequency transmitting anything, but white white noise works best because the operator might think they have a broken radio. We managed to spoof one Argentinian FOO in to believing his transmitter was broken by jamming every time he transmitted so the receiving station kept asking for repeats.

The higher power your radio and the more directional your antenna the better. Having a directional antenna protects your own forces that may be on the same or similar frequencies.

Someone asked if VHF can be affected by fog. It can. VHF is affected by the signal being refracted in different densities of air. That's what causes log range reception at times (tropospheric propagation). There's also ducting at sea level also caused by ducts of different densities of air. I once did some experiments on this across the Moray Firth. But it takes significant fog to make a difference noticeable on marine VHF with relatively unsophisticated signal strength measurements.

Agreed. As rain makes little difference its hard to see fog making a big difference. I would need to go back to theory but I can't remember anything in the formulas or other theory that gives signal loss due to atmospheric water.

Frankly I would be rather surprised if navies did not have a means of jamming AIS. Technically that can’t be too difficult.

See above.

Hello Pete,
technically, I have no idea.
The subject was aired at a few meetings between maritime operators/authorities, among the examples were the MRCC tried and contact by DSC a fishing boat in a rescue area but eventually they found there was no one; a high speed ferry diverted its course to avoid a fishing boat but found no one, etc.
I do not know the exact circumstances, but that seems to happen often enough to begin causing some concern. There was also an article in the SNSM (like RNLI) magazine, I ll look for it.
Myself have only had fishing boats suddenly "appear" on AIS, but that of course was simply they being in stealth mode for some time.

regards
r

I wonder if this is a fault in some equipment. Just recently my phone app that I use for giving me distances on the golf course has started playing up. It used to be very accurate but the past few rounds I've been concerned so yesterday I did some tests. I rebooted and had nothing open and it was giving me random distance. Looking at the plot of the picture it showed me in completly the wrong place by as much as 60 yds - a bit of a problem when you're 100 yds from the pin

I could believe that a vendor has a systemic problem that appears under certain circumstances or appeared after a software upgrade.

My experience round here is that fisherman who didn't want to be "seen" by their competitors just switched AIS off. A number of times I got a CPA alarm out of nowhere when a fishing boat I could see just appeared on my AIS chart.

 

[capnsensible]

https://ukdefencejournal.org.uk/nato-warships-test-electronic-warfare-defences-off-british-coast/

 

[NotBirdseye]

I spent 4 years in Germany working on jammers and intercept equipment, which was interrupted by the Falklands war when we took down some jammers and used them in the real world.

There's nothing special about jamming, all you need is a transmitter on the same frequency transmitting anything, but white white noise works best because the operator might think they have a broken radio. We managed to spoof one Argentinian FOO in to believing his transmitter was broken by jamming every time he transmitted so the receiving station kept asking for repeats.

Indeedy. One exception, military have more Watts at their disposal and some equipment is quite specialized very much different to the pre-cyberwar era. You should see sonar set ups nowadays .

As for a previous poster about the rules not stopping them from annoying the locals. Conducting exercises that aren't for general consumption (new tactics/equipment demonstration for example) means that your convenience takes a back seat over your defense but otherwise they do try pretty hard to make every possible allowance.

 

[PilotWolf]

I spent 4 years in Germany working on jammers and intercept equipment, which was interrupted by the Falklands war when we took down some jammers and used them in the real world.

There's nothing special about jamming, all you need is a transmitter on the same frequency transmitting anything, but white white noise works best because the operator might think they have a broken radio. We managed to spoof one Argentinian FOO in to believing his transmitter was broken by jamming every time he transmitted so the receiving station kept asking for repeats.

The higher power your radio and the more directional your antenna the better. Having a directional antenna protects your own forces that may be on the same or similar frequencies.


Agreed. As rain makes little difference its hard to see fog making a big difference. I would need to go back to theory but I can't remember anything in the formulas or other theory that gives signal loss due to atmospheric water.



See above.



I wonder if this is a fault in some equipment. Just recently my phone app that I use for giving me distances on the golf course has started playing up. It used to be very accurate but the past few rounds I've been concerned so yesterday I did some tests. I rebooted and had nothing open and it was giving me random distance. Looking at the plot of the picture it showed me in completly the wrong place by as much as 60 yds - a bit of a problem when you're 100 yds from the pin

I could believe that a vendor has a systemic problem that appears under certain circumstances or appeared after a software upgrade.

My experience round here is that fisherman who didn't want to be "seen" by their competitors just switched AIS off. A number of times I got a CPA alarm out of nowhere when a fishing boat I could see just appeared on my AIS chart.

I know it uses the wifi as well but I often have to use the find my iPhone app to locate where I left it, it is accurate enough zooms in to be able to tell almost exactly to a few inches of where it is - usually in plain sight!

We did a in in the Irish Sea, my iPhone was getting a better position, matching our installed equipment to a few feet than the survey team could get their equipment to acquire!

W.

 

[SimonFa]

I know it uses the wifi as well but I often have to use the find my iPhone app to locate where I left it, it is accurate enough zooms in to be able to tell almost exactly to a few inches of where it is - usually in plain sight!

We did a in in the Irish Sea, my iPhone was getting a better position, matching our installed equipment to a few feet than the survey team could get their equipment to acquire!

W.

That's why I said a fault. Normally when I use it its accurate to 1m or so and you can check that because you can see exactly where you are on the sat image. I've also checked against someone using a range finder and any number of other GPS apps.

 

[PilotWolf]

That's why I said a fault. Normally when I use it its accurate to 1m or so and you can check that because you can see exactly where you are on the sat image. I've also checked against someone using a range finder and any number of other GPS apps.

I understand, it was more a general comment on how accurate they are 'just being' phones.

W.