AIS "radar" information please

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pappaecho

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AIS \"radar\" information please

Following the loss of 3 lives last month off the Isle of Wight, I am considering the NASA AIS radar system, which requires either a separate VHF aerial or a splitter on the existing aerial so both radar and dsc radio share the same antenna.
But.... I have been told that if you transmit on the DSC radio, it wipes the complete plot off the AIS radar when a splitter is fitted.
Is this true?
 
Re: AIS \"radar\" information please

Can't answer your question - however general consensus on here appears to be to install a seperate VHF - probably not on the mast - for AIS so that you do not add in a point of failure to the VHF and have a backup antenna if you loose the otherone.
 
Re: AIS \"radar\" information please

NASA say that it should not be done with a splitter, although I do not know what the effect of going against this advice.
 
How much safer...

[ QUOTE ]
Following the loss of 3 lives last month off the Isle of Wight, I am considering the NASA AIS radar system

[/ QUOTE ] How much safer do you honestly believe you'll be? AIS only picks up the boats which are transmitting.
 
Re: AIS \"radar\" information please

hmm to be honest the Nasa set needs a separate aerial otherwise you get 25 watts of radiowaves burn straight through your AIS set and it will fry it!
 
Re: AIS \"radar\" information please

A decent splitter should not allow this to happen. Perhaps NASA also see this as a risk, Not too sure. Maybe worth asking them.

Safety - I think AIS is a good idea, particularly if you are not moving to a radar system. Some information is better than none. At last it will pick up the shipping, and give you information on their course and speed.

However the accident quoted - I do not think we know the circumstances yet. It could have been poor watchkeeping on the part of the yacht for all we know, so the feeling of safety that comes with electonics may not be an advantage, and could also lull you into a false sense of security.
 
Re: AIS \"radar\" information please

Wasn't aware pappaecho was .....
Nasa call it the AIS Radar system - however much we disagree with the Radar bit .... the majority of us know what it means.
 
Re: AIS \"radar\" information please

I have a NASA AIS which I installed last winter. I mounted a separate helix stub VHF aerial on the pushpit wired in such a way that I could use it as an emergency aerial for the VHF by simply swapping plugs over if I ever lose the mast.

This gives at least 10 miles range and is a great piece of kit. With it's guard range th AIS gave us much more confidence when sailing across the Channel in less than ideal visibilty.

I recommend it. No connection to NASA.

Ed
 
Re: AIS \"radar\" information please

A dedicated AIS splitter will NOT fry your AIS receiver - be it transmitting as voice or DSC. They are designed to protect against power output of 25/30 watt, depending on the product.
And it should not wipe the AIS blank, at least does not with all kind of AIS data receivers (NASA, EasyAIS, Trueheading i have tried) - have not tried the one with screen as it is very limited in the numbers of targets, and in heavy traffic situations shows only those that you are close-by ( and you see those anyway).
 
Re: AIS \"radar\" information please

[ QUOTE ]
Safety - I think AIS is a good idea, particularly if you are not moving to a radar system. Some information is better than none. At last it will pick up the shipping, and give you information on their course and speed.


[/ QUOTE ]

Watched a Discovery programme earlier today about Atlanta, the largest container ship in the world, (when it was built). They obviously use AIS, as well as everything else, and it looked extremely useful.... particularly when they were trying to identify those vessels which might be pirates.

Lets say it's foggy, and you have 20 vessels around you. Let's say you can get AIS detail which discounts say, 15 of them, as threats... you then need only worry about the other 5. The alternative is to take radar bearings of each one, or to make some assumptions as to which are not a threat.

There is no question that it is useful as an extra tool, as long as the user is aware of its' limitations.

My aerial is on the pushpit, (backup VHF if needed), but, having jammed a wrong sized BNC onto the unit... I'm in a state of flux as to whether to buy another unit, or dismantle the one I've got.
 
Re: AIS \"radar\" information please

Richard, I'm not sure that AIS is going to be very essential to you in the Med but if you have the kit you want to use it. Should be easy to change a connector. If you can't source locally, both RS and Maplin are happy to send to Spain (and presumably Portugal) at very acceptable prices. Sometimes manufacturers use crimp connectors but you will be able to buy solder versions - do make sure you don't order crimp by mistake (unless you have the specialist crimp tool, of course /forums/images/graemlins/smile.gif)
 
Re: AIS \"radar\" information please

Agree about the usefulness, but I think I like the toys <g>

I'll probably have a go at the connector when I've:

Fixed the steering
Fitted a galvanic Isolator
Found and stopped the tiny freshwater system leak
Found and stopped the tiny leak in the heads
polished the whole boat, waterline up
......... etc. etc. etc.

You know what it's like
 
Re: AIS \"radar\" information please

To be honest with myself, I fancy the toy myself /forums/images/graemlins/smile.gif But I can't justify it round here. The latest toy I'd like is a PDA with WiFi on a LAN set up as a repeat of all my instruments and the chartplotter. I'd be able to keep an eye on things while I'm off for a few hours. Has anyone done that, I wonder? I think I'd need to write the application and first I will need to do some serious study, being 20 years out of date with programming.
 
Re: AIS \"radar\" information please

Have you told Air Traffic Control?

You are correct that AIS is not Primary Radar. Air Traffic Control are relying right now on something you say is not Radar to control all the air traffic in the UK Air Space. They call it SSR, Secondary Radar or Secondary Surveillance Radar and it relies on the aircraft transmitting data to their aerial - just like with AIS where the ship transmits data to your aerial. If it's good enough for the Air Safety industry to call it SSR Radar, then it seems good enough to me that AIS is described as AIS Radar.

See this definition of Radar types.

The difference between AIS and Secondary Radar is that AIS transmits continuously whereas Secondary Radar transponders only transmit when interrogated. This is for historical reasons as SSR had its origins in WWII as an IFF - Identify Friend or Foe - system.

So AIS is not Primary Radar but it is a type of Radar and broadly the same type that is the main source of radar data for air traffic controllers all over the world.

Ed
 
Re: AIS \"radar\" information please

AIS and SSR are completely different technologies

SSR is 'attached' and synchronised with the primary radar return. It provides only limited data but is correctly described as radar

AIS is an autonomous ID & data system which provides a whole raft of information, totally independent and asynchronous to any radar fitted

It is most definitely not radar, primary or secondary
 
Re: AIS \"radar\" information please

Firstly let me say that I hate the term "AIS Radar" and consider it to be misleading. Further, I am amazed at the number of posts from folk who appear to think that it is in any way a replacement for radar as a tool for collision avoidance.

However, leaving that aside, purely from the definitions angle, exactly WHO defines what is meant by 'RADAR'. RAdio Direction and Ranging is where it came from but what does it mean now, and who is 'responsible' for maintaining the definition?
 
Re: AIS \"radar\" information please

[ QUOTE ]
AIS and SSR are completely different technologies



[/ QUOTE ]

Different yes. Completely different - No. Both are based on the principle that the target transmits data which is detected and plotted by the watching station. In both cases that transmission/transponder can be turned off by the target preventing the watching station from seeing the target. One is allowed to be called Radar and one is not. Why?
 
Re: AIS \"radar\" information please

Thanks all for your input.

I am aware of the limitations of the system. However it does give a spatial interpretation of the vessels and therefore possible threats. The MMSI system allow you to use the DSC radio to contact the vessel and make them aware of what you are and where you are. That in itself is significantly better than hoping that the vessel is not on autopilot, and that there may be a human looking out for other vessels. Four years ago a Merchant ship left Portsmouth, programmed into its course a heading which included the Nab Tower which it duly hit. (This was a first in the 90 odd years of its existance, no one had managed to hit it)

I have sailed in the Channel/Solent area on another boat fitted with AIS radar, and I am convinced that it is a useful tool, both for crossing the channel and for fog bound conditions where you can talk to other vessels in the vacinity, who are proably just as blind.

As regards siting of the separate aerial, it will go onto the pushpit, because it will be a nice easy installation, and it will give a backup to the VHF aerial on the mizzen.

Finally to the forum member from Ontario - here all vessels over 300 tonnes have to have one including warships, and certainly in the Solent area they are all working, albeit some do not have the current heading and destination programmed into them due to neglect,
 
Re: AIS \"radar\" information please

[ QUOTE ]
Firstly let me say that I hate the term "AIS Radar" and consider it to be misleading. Further, I am amazed at the number of posts from folk who appear to think that it is in any way a replacement for radar as a tool for collision avoidance.

However, leaving that aside, purely from the definitions angle, exactly WHO defines what is meant by 'RADAR'. RAdio Direction and Ranging is where it came from but what does it mean now, and who is 'responsible' for maintaining the definition?

[/ QUOTE ]

Hi Lemain,
Understand the question but question the relativity. Does anyone really care what it is called - we all know it is not a device as per conventional RADAR unit - and whilst I as yet don't have one - all I read indicates it is a great added navigational aid in avoiding other vessels.
Cheers
JOHN
 
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