Who’s driving that big rig (#1, AIS who?)?

Ben Ellison

Ben Ellison

Panbo editor, publisher & chief bottlewasher from 4/2005 until 8/2018, and now pleased to have Ben Stein as a very able publisher, webmaster, and editing colleague.

6 Responses

  1. DefJef says:

    WHat is amazing is how incompetant these captains and navigators are with all their expensive gear. One would think that they would use EVERY redundant means they have to confirm the situation. But they DON’T.
    I feel vert uncofortable around these huge vessels.. I don’t feel they are watching out. Where was their AIS alarms?????????????????

  2. Anonymous says:

    I can not believe the utter amatures that installed the AIS onboard that vessel WE ALWAYS interface AIS with Radars / ECDIS on large vessels

  3. Paul says:

    While I’ve seen mis-programmed “static” data before, I recently saw what I believe was an erroneous position report.
    While sailing from Hawaii to San Francisco a couple of weeks ago, I was passed by a cargo ship about a mile north of me. His position as reported by AIS was about a half-mile *south* of me.
    When I noticed this, I captured enough AIS and NMEA data from my system to be able to look at in detail later. He was reporting that he was operating in high-accuracy mode, so I don’t think I was seeing a dead-reckoning error.
    Has anyone seen this type of error before? Anyone care to suggest an explanation? I am discussing this in rec.boats.electronics now, if you would like to chime in there.
    (sorry if this posts twice — I’m figuring out how to use the TypeKey thing)

  4. GPSNavX says:

    Yes I once watched an AIS target (122′) track right through the middle of Treasure Island in San Francisco Bay. I was located on the Oakland Estuary so I could not see the target. The position was updating at the standard AIS dynamic data rate. Only saw this once.

  5. Paul says:

    Interesting… Any suggestions as to the reason for this position error, other than “broken GPS” which seems unlikely? I see no configuration error that would cause this.
    I wonder if some AIS systems may not correctly report when the GPS fix is lost?

  6. Paul says:

    I have found a possible explanation for the position offset error I saw (see my earlier post). “Dave” in rec.boats.electronics noticed an AIS-reported position error in a number of boats. It turns out they were using a Furuno GPS receiver with a user-programmed lat/lon offset to compensate for a local chart datum. This could definitely cause the problem I saw.
    Here are some U.S. Coast Guard and Furuno documents that discuss the problem:

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