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.
- 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
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
Australian tidal authorities have adopted the 20 year tidal datum epoch 1992 to 2011 as the basis for calculating tidal datum and the associated tidal planes.
In the 2010 edition of the Queensland Tide Tables, the semidiurnal and diurnal tidal planes of the standard ports were updated with the latest available tidal observations, prediction information and allowance for sea level rise. The 2010 tidal plane values for the standard ports will be fixed until the tidal datum epoch review in 2018 – unless a significant change occurs.
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.