Tide model calculator for @DrLucyRogers' SeeTide IoT device
This is the back-end for a device that displays how high the tide is at a specific location in real-time.
It is the code referred to in this blog post by @DrLucyRogers: SeeTide.
The blog post explains how you find your coastal location and plug it into the HTTP input node.
Tidal data is scraped from the UK Hydrographic Easy Tide web site once a day, and the flow creates a number of sine-wave models of the day's tide, peaking and troughing at the correct high and low tide times.
The model is then run every 5 minutes to compute how far in or out the tide currently is, and formats a string of RGB colours to send over MQTT to a neopixel display device that displays the green/blue mix to show land and sea.
The flow also uses cos (the first derivative of sin) to work out whether the tide is coming in or going out, and adds that onto the front of the colour string as a flag, which the device uses to light an LED indicating "in" or "out" direction.
Please note these calculations are simplified approximations of the tidal flows for the given location, and must under no circumstances be used for navigation or for any purpose that could in any way endanger life.
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