Tidal Information
The AHO provides a range of Tidal and Geodetic products and services.
Tidal Products and Publications
For more information on our range of tidal products and publications, please see our tidal products and publications below:
Tidal calculation information and diagrams are available in our resource library. These include calculations for high and low water at secondary ports, and a diagram for interpolating intermediate tide times and heights. Users can access these materials to support consistent calculation and graphical interpretation of tidal data.
Survey Operations Support
The AHO calculates the tidal planes for hydrographic surveys. This includes determining the relationship between Lowest Astronomical Tide (LAT) and Mean Sea Level (MSL), without which bathymetric soundings cannot be reduced to Chart Datum.
Cartographic Support
Accurate charts cannot be compiled without tidal information. The AHO determines an appropriate Chart Datum for every chart, supplies tidal and tide stream information for charts, and determines if and where tidal stream information should be shown.
Tidal Information Requests
The range of requests handled by the AHO is diverse, supporting activities such as offshore resource exploration, scientific studies and general enquiries from the public. Requests for tidal information can be made by contacting AHO Licensing.
Lunitidal Intervals
The lunitidal interval is defined as the time interval between the transit of the Moon over the local or Greenwich meridian and the next local high water or low water. It can be described as local or Greenwich, depending on the transit reference meridian; assumed to be local unless otherwise specified.
Lunitidal intervals can be calculated for any location but is meant for places where the semidiurnal component of the tide is dominant. The lunitidal interval changes through the lunar phase cycle. The variation about the mean is approximately +/- 30 minutes.
Please Note:
- Lunitidal intervals should not be used for navigation or any other critical purpose.
- Users are advised to use AusTides for higher quality predictions than what is available through The Bureau of Meteorology (BOM).
- State Authorities produce their own Official Tide Tables with time differences for secondary ports.
- Australian National Tide Tables (ANTT) and AusTides provide National coverage.
- Automatic Tidal predictions for Secondary ports are available using AusTides.
All locations listed in the ANTT can be found in the Lunitdal Interval 2024 attachment below. This table is updated every five years.
Tidal Glossary
Tidal terminology encompasses a variety of words and phrases to describe the movement of tides and related phenomena. Please see our Tidal Glossary for a list of common tidal terms and their definitions.