NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Reality Check: Navigating Around Hill and Dips
From: Trevor Kenchington
Date: 2003 Aug 30, 15:18 -0300
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 http://home.istar.ca/~gadus