Chart Datum

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Reference level on charts and for use in tidal predictions. It is approximately the lowest the tide is ever expected to fall because of astronomical phenomena, also known as Lowest Astronomical Tide (LAT)

Chart Datum is the reference level or plane from which all depths shown on a nautical chart are measured. It is typically based on the average low water level over a specific period of time and is used to ensure consistency in depth measurements for safe navigation.