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    Re: Uss Lamoure County
    From: Stacy Hanna
    Date: 2004 Jan 25, 18:27 -0500

    While I agree that it was not a GPS error, it was an error caused by
    relying only on GPS. If the ship had been using radar navigation (as it
    was required to do by navy instructions in a low visibility situation
    that close to land) they would have noticed the discrepancy with GPS and
    hopefully would have stopped the ship (or turned back to deeper water)
    until they could determine the cause of the error. As I stated in an
    earlier message, a good navigator uses every available means to
    determine his position and doesn't place full confidence in ANY single
    system. (A sextant, unless used for horizontal angles(not possible in a
    low vis situation, the same as any other visual piloting), would also
    have been an inappropriate way of fixing the ships position that close
    to shore but soundings and radar ranges could have probably prevented
    the loss of the ship)
    
    -----Original Message-----
    From: Navigation Mailing List
    [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] On Behalf Of Jared Sherman
    Sent: Sunday, January 25, 2004 17:26
    To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
    Subject: Re: USS LAMOURE COUNTY
    
    Joel-
      GPS only on Chilean charts that used a local datum without taking into
    > account the datum shift.>
    
     That's the bottom line. This was not a GPS error, this was a
    navigational DATUM error ("pilot error" as the FAA calls it) caused by
    using *any* means of determining position, and then incorrectly applying
    it to local charting. If they had used a sextant, they would have still
    run aground because they still would have been using the wrong charts
    (wrong chart datum) to go with their position.
    
     Apparently the GPS reliably did what it was supposed to do, as it was
    supposed to do. And the navigator did the unforgiveable, entering shoal
    waters after incorrectly charting his position.
    
     By the way..."USS" would be a US merchant steam ship, as I understand
    it. "USN" would be a US Naval vessel. A similar small mistake is all it
    takes to get the datum wrong, regardless of the method for obtaining
    position fixes.
    
    Well, unless you're using rods and chains stretched from the beach.
    Then we can still miscount the chains.
    
    
    

       
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