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    Re: Reality Check: Navigating Around Hill and Dips
    From: Trevor Kenchington
    Date: 2003 Aug 30, 15:18 -0300

    David Hoyte asked:
    >         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?
    I do not know what methods are now used to extract the parameters of the
    various sine-wave tidal constituents from tide-gauge records. I assume
    that hydrographer's use statistical analysis software of some kind but I
    cannot confirm that, let alone say what software is used.
    It shouldn't be a very demanding process. The frequency of each
    constituent is known so it is just a matter of getting the best fit to
    the data by adjusting amplitudes and phase angles. The only real problem
    is that you should use 18+ years of data, with heights of tide measured
    at frequent (hourly?) intervals through that time, which makes for a
    fair amount of data. That was a mind-numbing process before modern
    computer capabilities but might only be a few minutes work with a
    desk-top machine.
    Trevor Kenchington
    Trevor J. Kenchington PhD                         Gadus@iStar.ca
    Gadus Associates,                                 Office(902) 889-9250
    R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
    Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555
                         Science Serving the Fisheries

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