N22 tides highest-high lowest-low PROVISIONAL

Preamble

This is "the crowning glory" so far of my "Pointless processing of the Newlyn tide-gauge 2022 data".

Happy due credit to instigator

Tide data gratefully received from the British Oceanographic Data Centre (BODC) [external link].

What's happening here...

Two things here:

"awk" scripts which do what they do to the Newlyn all 2022 tide data
graph plot of the output of that "awk" script

["awk" - external links : Free Software Foundation (very technical), Wikipedia (general overview)]
["awk" is one of the "unix (user) toolkit" - see eg Unix philosophy (Wikipedia external link)]

The data they are processing

Sample from BODC's Newlyn all 2022 tide data:

  Cycle    Date      Time    ASLVBG02   Residual  
 Number yyyy mm dd hh mi ssf         f          f 
 ...
 29998) 2022/11/09 11:15:00     1.224      0.172  
 29999) 2022/11/09 11:30:00     1.206      0.176  
 30000) 2022/11/09 11:45:00     1.240      0.193  
 30001) 2022/11/09 12:00:00     1.310      0.206  
 30002) 2022/11/09 12:15:00     1.419      0.216  
 ...

of which the 4th column is the measured sea water height above LAT (Lowest Astronomical Tide), ie above nautical chart datum.

This sample is selected because it can be seen graphed around datapoint 30000 here (in webpage Newlyn 2022 tide cycles samples ).

The scripts

Seeking to find the highest point of the high tides:

awk '
BEGIN {dpcnt=0; dpval=0}
{
if ($4 > dpval && $4 < 6.2 && $4 > 2) {dpcnt=NR; dpval=$4}
else if (NR > dpcnt + 32) {print dpcnt, dpval; dpcnt=NR; dpval=0}
}
'

Seeking to find the lowest point of the low tides:

awk '
BEGIN {dpcnt=0; dpval=3.5}
{
if ($4 < dpval && $4 < 3.5 && $4 > 0) {dpcnt=NR; dpval=$4}
else if (NR > dpcnt + 32) {print dpcnt, dpval; dpcnt=NR; dpval=3.5}
}
'

Where, as best I can be bothered to explain:

$4 is the 4th column with seawater height above LAT
NR is awk "Number of the Row" variable (ie "line-number")
6.2, 2, 3.5, 0 are plausible maxima/minima regarding seawater height
32 is a time-elapsed - 32*15min; (* 32 0.25) => 8.0 hours (the tide cycle is 12hr 25min, so 8hrs must mean being on the next rising/falling tide)

The graph of the scripts output

You might if you feel like it compare this to...

... the plot of all the 2022 Newlyn measured sea height data-points.

Credits

Thanks go to Reddaway's cider of Luton, Devon [external links: (Facebook) (ciderexpert) (ratebeer) ] for assistance with my thought processes. My recommendation "Very Dry" which after overcoming digestive malady (about 2 days) is the real natural authentic cider (add honey (eg half-teaspoon) at time of drinking if the cider is too tart to be drinkable).

(R. Smith, 28Apr2023 to 29Apr2023, 30Apr2023 (eds.))