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    Reality Check: Navigating Around Hill and Dips
    From: David Hoyte
    Date: 2003 Aug 30, 10:12 EDT

    >> I wrote, 8/13/2003:

    >>      Gravity anomalies cause the geodic heigh of the ocean's
    >> surface to vary around the world by up to 200 meters, 650 feet. Ref:

    http://www.csr.utexas.edu/grace/publications/press/03-07-21-ggm01-nasa.html

    >>      I heard as far back as 1975 that a large ship will use
    >> significantly more fuel if it passes down into a gravitational dip
    >> and climbs the other side, rather than following a longer path
    >> around the dip which will keep it more "on the level".
    =========

    > Response from George Huxtable, george{at}HUXTABLE.U-NET.COM:

    > I am a natural sceptic about most matters, and here's another to be
    > sceptical about.

    > I just don't believe it. On the ocean surface there are no
    > gravitational dips.
    =========

    George,

            Being loath to abandon a little-know fact, after it had been
    imparted to me with all the 110% confidence of a former officer of
    HM Royal Navy, in my briefing to transfer technology to the then
    USSR, I have carried out a "Reality Check" on your assertions.

            Not just a single mariner, who would doubtless have just as
    much confidence in his reply as that former Naval officer:  I consulted
    the team responsible for instructing the captains of a fleet of 25
    tankers and other ships of a major oil company on the courses they
    are to follow as they traverse today's oceans, week by week.

            This oil company has an active Research Department, where I
    worked some 50 years ago.  I felt sure that at least one of their
    highly-competitive scientists, sometime in the last 25 years that the
    gravitational hill-and-dip phenomenon had been known, would have made
    his mark on the company by saving their tanker fleet vast sums of
    money in time and fuel by having their ships skirt the anomalies.

            And I was right about the place to ask. The answer came back
    loud and clear by return of email:

            The seagoing fleet of this major oil company pays no attention
    whatever to the gravitational hills and dips in the oceans as they
    navigate the oceans of the world. To a ship's captain, knowledge of
    these gravitational rises and falls in the ocean's surface are clearly
    superfluous: they affect neither the time nor the fuel used in a sea
    journey.


            George, I must thank you (in particular) for your patience in
    explaining the physics of the matter in such an understandable way.


            Interestingly, a friend tells me the question of the sea level
    being higher in an area of high 'g', was used as a physics-class
    problem in his Canadian college courses, some 20 years ago.


            On the matter of complex cycles in tidal movements: I was
    at one time involved with computer programs to identify cyclic
    interactive processes, such as a cement kiln. The program gave the
    plot of amplitude-vs.-frequency for each variable in the process:
    cause and effect could be identified by their similar frequencies.

            Programs of this type were in an advanced state of develpment
    by Prof. Ashikaga at University of Tokyo, in 1985.

            Tidal movements in the ocean were commonly used as a test for
    these programs: Are these same programs now used as the primary
    method for the analysis of tides, do you know?


            George, Thank you again for helping to educate me.

            Take care,  David.  (DavidHoyte---.com)
       
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