Can you explain what are shallow water corrective terms (f4 & f6) ? I study on tides for many years, but I never hear about these terms. If these terms mean oscillations with some specific frequencies, I think you can use S_TIDE which is developed by me (https://www.researchgate.net/project/A-non-stationary-tidal-analysis-toolbox-S-TIDE). Using S_TIDE, you can extract oscillations at any frequencies.

Thanks for your reply.

There is a relatively old method to estimate tidal harmonics called UKHO simplified (simply they call it Admiralty method). In this method, the calculations are based on the main harmonic constituents O1, K1, M2, S2 and adjustment for shallow-water fourth- and sixth-diurnal amplitudes and phases (f4, F4; f6, F6).

And thanks for introducing your code. I like to try it for some uneven sea level observations.

Hi Mustafa, The Admiralty Tide Tables publication used (up to 1999) to include a simplified harmonic method that could be used on a calculator to generate tidal predictions. I have attached a scan of it here. I have found code (fortran 4 as a print out) from the Australian National Tide tables 1991 that generates tide predictions using the admiralty method also and attached here.

Regards