Tide heights chart datum 1

Let’s have a closer look at “Tidal Heights” and “Chart Datum”.
On nautical charts, soundings and drying heights are measured from Chart Datum.
Chart Datum is the Lowest Astronomical Tide or L A T , meaning the lowest level to which the tide is expected to fall. All depths on a chart are measured below chart datum and all drying heights are measured above it.
Non-drying heights, for example a lighthouse, are always measured above Mean High Water Springs, not Chart Datum, as an added safety margin.
The height of tide is always measured above Chart Datum.