The spokes of the wheel are lines which represent the crest of the tidal wave. If it is high tide at B, it is high tide all along the line which extends from B to the amphidromic point. This is called a 'cotidal line': all points along the line experience
The circles in this image are labeled '1m', '2m', and '3m'. These are tidal ranges. (Remember this is the difference in water height between high tide and low tide). All the points along the circle labeled '3m' have a tidal range of 3 meters. All the poin
