# How do I determine the phase lag for a tide

I want to determine the height of a sine wave for some tidal constituents for which I would use the following equation: ๐(๐ก)=๐ปcosโก(๐๐กโ๐), where H is the amplitude, ๐ is the speed of rotation, t is the time elapsed and ๐ is the phase lag. If I have got the following data for a site, how do I determine the phase lag so that I can calculate Y(t).

Constituent M2, Amplitude 3.18, Degrees per hour 28.984, Radians per hour 0.5058, Phase degree 173

• Worth checking up on... is this a homework question (or where are you getting the data, may be of interest to people, if not) Nov 10, 2022 at 18:58
• And are you needing to produce the entire time function of height, or just the "height of the sine wave" (which isn't as involved at all) Nov 10, 2022 at 18:59
• It is from a paper Swansea Bay Tidal Lagoon Annual Energy Estimation by Petley and Aggidis. I was just wanting to work out the height of the sine wave to then use in energy estimates with coding Nov 18, 2022 at 15:04
• So more than just the peak height (which is of course the amplitude) I take it! (Hopefully you can understand why I had a wonder if it was a homework question, many times in undergrad they'd ask questions like that, wanting the max height, and giving a fairly involved trig function, and people would get lost trying to compute it all , when it's right there given by the amplitude). But sorry, have no more clue than that, upvoted, as it's an interesting looking question Nov 19, 2022 at 4:58