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Hi there Correction: Goofed maths - expected number of "peak of high tide" and "minimum of low tide". (/ (* 365 24) ;; 8760 ;; hrs in a year (+ 12 (/ 25e0 60)) ;; 12.416666666666666 ;; hrs per tide cycle ) ;; 705.503355704698 So expect 705 or 706 highest high's and lowest lows of the tidal height in a year. > On 23 Apr 2023, at 18:16, rds_met <dcglug@xxxxxxxxxxxxxxx> wrote: > > Hi all > > Thinking of a project. > All 35040 data-points of Newlyn 2022 tide-gauge data - recorded every > 15 minutes = 4 datapoints per hour. > Graphed in-entirety it looks like this > http://weldsmith.co.uk/nautical/230323_th_newlyn_22all/pics/tide_newlyn_height_all.png > > Idea is to sequentially "crawl" the data extracting the highest high > and the lowest low of each tide-cycle, so can have a plot with two > corresponding lines - the highest-high and the lowest low. > > That should extract 352 or 353 > (/ (* 365 24) (+ 24 (/ 50e0 60))) ;; 352.751677852349 > highest-highs and lowest-lows in the year of 2022 > > The data presenting the cycles of the tide should look like this > sample from 22:15,08Nov to 00:15,10Nov. > http://weldsmith.co.uk/nautical/230323_th_newlyn_22all/pics/tide_newlyn22_ctr30k.png > Which is "smooth". > But wind, waves, a boat going past the tide-gauge, etc. could mean the > first "drop"/"increase" might not the highest / lowest of the tide > (respectively). > However, prior knowledge about the tide cycle at 6hrs 12~1/2mins > hi-to-lo / lo-to-hi means you can finish the search by an hour or two > after the expected highest / lowest. > > So - an overall approach and an algorithm... > > Anyone interested to participate in a group effort? > Credit to the DCGLUG group. > > Languages by a mild preference for me would be Lisp or unix > shell-script. > However any other good selection could be considered. > > ?? > > This is in my series "Pointless processing of Newlyn tide data". > It's a project for if I need an intermission from building renovation > work. > Lining it up for if that juncture comes. > I'm not in the South West at the moment, by the way, so cannot easily > be a meet-in-real-life collaboration. > > I've just sailed crewing a yacht on the Bristol Channel > http://weldsmith.co.uk/nautical/230417_ph_to_mh/230417_ph_mh_wp.html > "Voyage Portishead to Milford Haven" > to give some idea of the type of connection I have - the connection > between the data and the reality. > By the way - half the crew were unsuccessful in maintaining a > successful relationship with their last meal on that voyage. > Despite deliberately timing the voyage to be on a neap tide. > > [ > http://weldsmith.co.uk/nautical/230323_th_newlyn_22all/pics/tide_newlyn22_ctr30k.png > shows overall the 2-week pattern of neaps and springs which my > proposed algorithm and its output graphed would neatly present > ] > > Digression note - text-editor emac's built-in function > "phases-of-moon" lists the lunar cycles, which within a day enables > you to know the nautical cycles of neaps and springs without having to > go look up from the tide-tables. Springs are at new and full moons; > neaps are at the half-moons - the "quarters" of the lunar cycle. > > So anyway; takers for a group project? > > Regards, > Rich Smith > -- > The Mailing List for the Devon & Cornwall LUG > FAQ: https://www.dcglug.org.uk/faq/ -- The Mailing List for the Devon & Cornwall LUG FAQ: https://www.dcglug.org.uk/faq/