A line of equal tidal range or amplitude, drawn on the same charts as cotidal lines. Around an amphidromic point corange lines form rough rings, with range rising from zero at the centre toward the coasts. Read together, cotidal and corange lines let a planner estimate both the timing and the size of the tide anywhere in a basin, which is the basis of tide zoning and model validation.
Corange lines go from 1 metre at the mouth to 4 at the head of the bay, so scale the range ratio along the survey.
Also heard as
- co-range line
Related terms
Cotidal line
A map line through every place where high water of a tide or constituent arrives at the same moment.
Amphidromic point
A point in the sea where a tidal constituent has zero range and around which its high water rotates.
Tidal range
The vertical difference between a high water and the neighbouring low water.
Subordinate station
A location whose tides are predicted by applying time and height corrections to a nearby reference station.