Modelling tide to look for submersion tide

Hello, I need some help since I have just started using Matlab. I would like to build a model representing the tide in order to have a monthly submersion time. Anybody can suggest me the sinusoidal function to use please? thank you

[Wayne King]

Can you please define what a monthly submersion time is with respect to tides?

Answer 1

[Kelly Kearney]

Tides are a bit more complex than just a simple sinusoid. The t_tide toolbox can generate predicted tides at a given location, given a subset of harmonics ( http://www2.ocgy.ubc.ca/~rich/#T_Tide ). There seem to be several options on the File Exchange as well.

[chiamag]

My idea is to work on tide data of past years. Therefore i do not have to predict them.I have data of low and high tide for a given area. I would like to find a way to express the submersion time for a point in order to check which are the areas in a lagoon system that are regurarly, rarely or never submerged.

Answer 2

[Image Analyst]

Let's say your data is in a variable called tideHeight. Let's say there is a particular object (a roadway, a signpost, a rock, a turtle's nest, or whatever) that is submerged when you tide height is more than 9. Then you can find elements where it's submerged by doing this

% A logical (true/false) vector 1,0,0,1,1,1,0,0,1,0,0,1,0 or whatever.
itsSubmerged = tideHeight >= 9;  
% Find actual index numbers: 1,4,5,6,9,12
submergedIndexes = find(itsSubmerged);

Then you can look at diff(itsSubmerged) to find when it just starts being submerged:

starts = find(diff(itsSubmerged));

That will help you figure out what the period should be for your sine wave model.