coopec
N/A
I've read about CPA and TCPA andI Ï can see that if you had "one's own dedicated receiver incorporated with the transponder" it becomes useful.
I've always considered a radar: something to think about.
Clive
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Automatic Identification System (AIS) Marine Traffic
- Thread starter coopec
- Start date
I've read about CPA and TCPA andI Ï can see that if you had "one's own dedicated receiver incorporated with the transponder" it becomes useful.
I've always considered a radar: something to think about.
Clive
coopec
N/A
Here's the answer
While AIS has been deployed globally, it suffers from a major limitation because Earth’s curvature limits its horizontal range to about 74 km from shore. This means that AIS traffic information is available only around coastal zones or on a ship-to-ship basis.
Tracking ships using microsatellites (SAT-AIS) solves this problem. The ship’s identity is recorded and decoded by satellite then sent to ground stations for further processing and distribution
SATELLITE- AUTOMATIC IDENTIFICATION SYSTEM (SAT-AIS)
http://www.esa.int/Our_Activities/T...ite_-_Automatic_Identification_System_SAT-AIS
While AIS has been deployed globally, it suffers from a major limitation because Earth’s curvature limits its horizontal range to about 74 km from shore. This means that AIS traffic information is available only around coastal zones or on a ship-to-ship basis.
Tracking ships using microsatellites (SAT-AIS) solves this problem. The ship’s identity is recorded and decoded by satellite then sent to ground stations for further processing and distribution
SATELLITE- AUTOMATIC IDENTIFICATION SYSTEM (SAT-AIS)
http://www.esa.int/Our_Activities/T...ite_-_Automatic_Identification_System_SAT-AIS
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BrianH
Well-Known Member
I sailed with an AIS receiver only for seven years before upgrading to a transponder/receiver unit two years ago. The receiver was invaluable when crossing the busy shipping lane out of Trieste, allowing me to precisely time my dash between ships by observing the CPA of the next in line.
The purchase cost and power requirements of even transponder/receiver are minimal compared to radar.
RichardS
N/A
That "line of sight" limitation is not the whole story: see http://www.ybw.com/forums/showthread.php?457184-Masthead-VHF-antennas
However, as they are trying to sell satellite AIS tracking I can see why they would want to down-play the range of conventional AIS, even if their 74 km range is actually very fair.
Richard
Amulet
Well-Known Member
I won't hear AIS knocked. The internet based version is something of a toy, but I use it often at home in Oban to find interesting things. E.g., I'd forgotten that the Waverley was coming by, but saw the funnels from my bedroom window and cross-checked on MarineTraffic. The internet system depends on (volunteer?) shore stations and their range, so of course there's lots you can't see. It also often sends very stale data. This can mean that the on screen position can be a mile out from the actual position. I can see them from my balcony so I know.
Real AIS is a boon. I navigated my way out of Dover in the dark in the fog through a maze of ferries.
It's a shame, but the existing AIS protocol cannot operate from satellite receivers as they can't resolve messages from senders using the same time slots but far apart on the earth. Receivers on earth could never see both so it works ship to ship.
Real AIS is a boon. I navigated my way out of Dover in the dark in the fog through a maze of ferries.
It's a shame, but the existing AIS protocol cannot operate from satellite receivers as they can't resolve messages from senders using the same time slots but far apart on the earth. Receivers on earth could never see both so it works ship to ship.
coopec
N/A
There's an interesting YBW thread comparing the attributes of radar and AIS which I think puts everything into perspective.
Practical Boat Owner's Reader to Reader
AIS vs radar
http://www.ybw.com/forums/showthread.php?280041-AIS-vs-radar#W03L7sDmu6b2w1oq.99
Clive
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TwoHooter
Well-Known Member
Certainly not so at the moment. Vesselfinder has us still making our approach to the Yealm on 19 July. Marinetraffic has us in our correct position. I think Vesselfinder is a bit easier for our non-boating friends and family to use but if they don't smarten up their act I'll stop suggesting Vesselfinder.