A UK chart gives the height of this light as 15m. Which level is that measured above?
A lighthouse on a cliff, with a label pointing at its lamp that reads: light 15m, above which level? Four dashed levels are drawn across the water beside the cliff. From the top: mean high water springs, mean sea level, mean low water springs, chart datum.
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Mean high water springs. On UK charts of tidal waters the elevation of a light is given above mean high water springs (MHWS). Depths and drying heights use a different level, chart datum, which is close to the lowest the tide is ever predicted to fall.
