Skip links and keyboard navigation

Tidal planes

The semidiurnal and diurnal tidal plane tables give the height of the mean tidal planes and the average tide time differences at different places on the Queensland coast.

The form of the tide changes as you progress north along the Queensland coast. 

For places:

  • south from Lindeman Island refer to the section semidiurnal tidal planes
  • in the Torres Strait and the Gulf of Carpentaria refer to the diurnal tidal planes section
  • between Lindeman and Torres Strait, where the classification may be either semidiurnal or diurnal, you will need to refer to both the semidiurnal and diurnal tables.

Semidiurnal and diurnal tidal planes

NOTE: the 2022 edition of the standard ports' semidiurnal and diurnal planes have been determined using the Tidal Datum Epoch 2010 to 2029 and are given as heights above the Queensland Port Datum (LAT(1992)).

* For reference to AHD please source the relevant Permanent Mark AHD levels from  Queensland Globe ( for comparison against LAT.

The term semidiurnal refers to a tide which has a period or cycle of approximately half of 1 tidal day (about 12.5 hours). Semidiurnal tides usually have 2 high and 2 low tides each day. The tides at Brisbane Bar are a typical example of semidiurnal tides.

The tides south from Lindeman Island (latitude 20 degrees 28 minutes south) are classified as semidiurnal.

A guide to semidiurnal tidal planes.

The term diurnal refers to a tide which has a period or cycle of approximately 1 tidal day (about 25 hours). Diurnal tides usually have 1 high and 1 low tide each day. The tides at Karumba are a typical example of diurnal tides.

The tides of Torres Strait and the Gulf of Carpentaria are classified as diurnal.

A guide to diurnal tidal planes.

Tidal datum epoch and update of tidal planes

The tidal datum epoch is the recommended interval for the calculation of tidal datums. Australian tidal authorities have adopted the 20 year Tidal Datum Epoch 1992 to 2011 (inclusive) as the basis for determining Lowest Astronomical Tide (LAT). This Tidal Datum Epoch is known as LAT(1992). Queensland has moved to a tidal datum epoch 2010 to 2029 for tidal plane determination excluding LAT.

In the 2022 edition of the Queensland Tide Tables, the semidiurnal and diurnal tidal planes of the standard ports' were updated to incorporate the latest available tidal observations, prediction information and allowance for sea level rise, i.e. they have been determined using Tidal Datum Epoch 2010 to 2029 and given as heights above the Queensland Port Datum (LAT(1992)). It is intended that the 2022 tidal plane values will now remain fixed until the tidal datum epoch is reviewed or significant changes occur.

The tidal planes of the secondary ports were also updated to match the changes at the standard ports, however, the secondary port tidal planes are updated as new observations become available.

Last updated
11 November 2021