So you thought it was lonely out at sea

cor ... Gib strait is busy

A few years ago, I came within a fag papers width from being rundown by a Tanker
going southbound. Oh gawd... nurse where's me tablets..
 
emandvee44 said:
AIS data transmissions can only be received by other vessels or shore based receivers, and the range is limited to VHF range.
Thousands of the vessels were far from land.

M.
Click to expand...

Think outside the box!!!!!! AIS is easily transmitted by other means as well so that Uncle Sam and others and snoop on who goes where!:)
 
emandvee44 said:
AIS data transmissions can only be received by other vessels or shore based receivers, and the range is limited to VHF range.
Thousands of the vessels were far from land.
Click to expand...

Although AIS operates on VHF frequencies, it is not as constrained as VHF radio reception (the reason was explained to me a while back, but it's gone into the senior memory bank). For instance a beacon at Madrid airport is clear on AIS receivers in the Canaries, over 1000km away. In fact this signal is sometimes used locally to check new installations. Equally, AIS signals are often visible over substantial hills: vessels in Horta, for instance show a clear signal well off the other side of Faial, which is over 1000m high.

As to your original point: yes! One of the scariest things about first using AIS is just how much stuff is out there...most of it too distant to be of any concern, but salutory, nonetheless.
 
Last edited:
emandvee44 said:
AIS data transmissions can only be received by other vessels or shore based receivers, and the range is limited to VHF range.
Thousands of the vessels were far from land.

M.
Click to expand...

There is provision in AIS protocol for hopping. I.e. for data from one transmitter to be received by another and retransmitted.
So the reach is not limited to a single VHF hop.
 
Bilgediver said:
Think outside the box!!!!!! AIS is easily transmitted by other means as well so that Uncle Sam and others and snoop on who goes where!:)
Click to expand...

I'm sure you meant to say " is easily RECEIVED by other means ".

Thinking beyond the box you've put yourself in, what makes you think everyone is broadcasting on AIS, or on a 300+ tonne vessel? (where AIS is supposed to be mandatory).

If you have eyeball and AIS coverage of Plymouth Sound (for example), you will regularly see stuff passing by that is often much bigger than 300 tonnes displaying no AIS signal at all. And these are the Good Guys.
 
So you thought it was lonely.....

I have just read the fleetmon website, which I should have done before I first posted:o; it is all explained there , although I did not know the technology existed nearly a year ago. It is however interesting that AIS signals which are transmitted horizontally and have a generally line of sight range, can be picked up by a satellite a couple of hundred miles above.

I would think that with all the publicity about this, there will be a lot of vessels switching off their AIS sets:) - not us though.

M.
 
emandvee44 said:
I would think that with all the publicity about this, there will be a lot of vessels switching off their AIS sets:) - not us though.
Click to expand...
Any vessel approaching the USA that has ever been seen switching off its AIS gets special attention from the US coast guard and other in port vessel checks. All SOLAS vessels have to submit all sorts of information prior to entering US waters. To aid this process a system called long range vessel reporting is being standardised.
 
Vhf is line of sight. If you look up there are any number of satellites capable of receiving the signals and not a single thing in the way to obstruct the signal.

The title of the vido is 'fleetmon satellite ais'
 
Last edited:
You must log in or register to reply here.

Share this page

Top