Tidal datum information

The vertical reference level for each standard port is the port datum. Since 1994, this datum was set to the lowest astronomical tide (LAT) at Queensland ports. To define this datum a tide gauge benchmark (TGBM) is established. The height of this benchmark, relative to LAT, is then used to define the port datum onsite.

The vertical distance between the tide gauge benchmark (or best recovery mark where the tide gauge benchmark has been destroyed/disturbed/is unstable) and LAT is given in the Semidiurnal and diurnal tidal planes tables.

The official tide predictions for Queensland standard ports are given as heights above the port datum (LAT). To account for changes in sea level, an adjustment is made to the mean sea level estimate. This mean sea level is used as the basis for tide predictions.

Mean sea level used for the tidal predictions for 2025

An allowance of 2.7mm per year for sea level change has been made in the mean sea level (MSL) estimate. The allowance is calculated from the central date of the observation period to the central date of the prediction year. The heights are referred to Queensland Port Datum.

Please refer to 2025 Tidal Planes for permanent marks and the Queensland Port Datum reference level. Australia height datum levels or details for determining Australia height datum levels for permanent marks can be sourced from Queensland Globe.