Having seen John Keys collaborative piece at the Exchange Gallery, Penzance, I looked up his website and found some excellent pictures of his work for Tidal 28. The picture, above, shows part of the ramp wall lit at night - quite different to the daylight impression.
Tidal Cliff (right) and Tidal Sandbar (below) are two of his drawings that chart the tideline from a specific point. It is vertical sections from these drawings that have been enlarged to make the panels for Tidal 28. Described on the website as 'Acetates' each drawing has several layers, to form a composite whole.