Who uses AIS?

Discussion in 'OnBoard Electronics & Controls' started by cthippo, Oct 20, 2010.

  1. fairbank56
    Joined: Dec 2008
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    fairbank56 Junior Member

    Well, you'd think those "professionals" in the US Navy would get it right, but I see a Navy warship at anchor on a port visit with the first three MMSI numbers of 269 when it should be 369. 269 is for Switzerland. This is why the stupid recreational boaters aren't allowed to program their class B transponders. Only the experienced "pro's" are allowed. Duh.

    Eric
     
  2. apex1

    apex1 Guest

    Yeah.........:D

    ...and maybe non smoking Ukrainian Bigamists.
     
  3. fairbank56
    Joined: Dec 2008
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    fairbank56 Junior Member

    Turns out that this is a brand new ship on it's way to it's commissioning ceremony in Florida next month. The error was probably done by installers at Bath Iron Works Shipyard in Maine and nobody has caught the error yet.

    Eric
     
  4. Submarine Tom

    Submarine Tom Previous Member

    Over responding to a MAYDAY, gee, I can think of much worse. They are simply attempting to determine which antenna is closest.

    Feel fee to provide your position so they may get on to a MAYDAY RELAY and dispatching your rescue vessel.

    -Tom
     
  5. michael pierzga
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    michael pierzga Senior Member

    Ais is a very useful tool for a small craft. Small craft radar, with an alert operator. picks up vessels at 8 miles. Long before you have picked up the vessel on radar you see them with AIS. This allows you to be better prepared for waves of traffic in areas like the English Channel. Gib, the Sicilian Channel. Good stuff..and not expensive.
     
  6. apex1

    apex1 Guest

    You will find rather different opinions when you read the entire thread, Michael.
    It is NOT the "small craft radar" as many like to believe.
     
  7. dskira

    dskira Previous Member

    Thank you for your explanation. I was afraid it was a Navy error.
    But you right, the janitor at BIW made it all wrong, and 2 thousand electronics engineers from the Navy are absolutely right.
    DUH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
     
  8. michael pierzga
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    michael pierzga Senior Member

    Its not a radar..it assists the radar operator on small yachts with picking up targets over the radar horizon
     
  9. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    How does a line of site VHF see further than line of site RADAR?
     
  10. RHough
    Joined: Nov 2005
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    RHough Retro Dude

    Hmmm ... VHF ant 23-40 ft above sea level ... radar 15 ft above sea level ... tip of AIS VHF transmitting ant is a bad radar target?

    Good question ... :p
     
  11. Milan
    Joined: Apr 2005
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    Milan Senior Member

    Development is space based tracking (satellites) – so signals travel more or less vertically, much less distortion from the high waves, obstacles on the coast line e.c.t.

    I don’t know how much coverage at he moment is from the space but it should be complete pretty soon.
     
  12. fairbank56
    Joined: Dec 2008
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    fairbank56 Junior Member

    I sent an email to the ship on Saturday and they replied thanking me for the information and that they have informed the ships navigator and hope it is a quick fix. They are getting underway as of this moment but have yet to fix the problem.

    Eric
     
  13. michael pierzga
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    michael pierzga Senior Member

    On a small craft in a seaway the seaclutter forces the operator to retard the radar sensitivty to achieve a decent reflection .the AIS signal is visable when the the fishing boat or ship is hidden from the radar sweep. One of the challenges for small craft in shipping lanes is predicting the expected traffic flow. Is now a good time to bear off and cross the shipping lane on a perpendicular ? I can hear all the ships talking on the vhf clarifing Red to Red.. inbound outbound.....but I cant see them..
     
  14. apex1

    apex1 Guest

    And you can´t see those having no AIS either!

    Hence my comment, it is NOT a replacement for a radar, it is just another tool for the ease (or complication) of navigation.

    And the comment on range was wrong. VHF signals travel over obstacles, radar signals don´t. Therefore I can "see" objects hidden by hills, buildings and the like, if they are AIS equipped. But I cannot see the 30 meter Gin palace coming round the jetty at 20 kn if I have no radar!
    Those who cannot manage a clear picture on a radar screen (seaclutter, rainclutter, etc) should not use it! But then we would not see many radar on yachts and boats.

    Regards
    Richard
     

  15. michael pierzga
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    michael pierzga Senior Member

    It is just a tool..a good tool Dont underestimate how difficult it is ,even for an experienced operator, to tune a radar to see thru wet sails, 2 or 3 meter waves and rain squalls. Many times, inshore, the radar ,and we only carry one radar, is optimised on range and tune to sweep very close, 2 to 4 miles, to seek and avoid small inshore fishing craft, rubber ribs, longline buoys..... easy to miss the obvious coming over the horizon at 18 knots. Another good feature of AIS is VTS protocol. I remember this summer listening in on the Rio Rio traffic controler as he struggled to voice communcate with an Albanian tanker to alert of shipping movement ahead. . ... Nice tool. Id suspect commercial guys would prefer that yachts not carry them or else in a few years the AIS system will become so overcrowded with targets that your eyes go cross. Imagine what the AIS display ,when approaching the Kiel Canal ,would like like during Kieler week ?
     
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