The Tides & Sea Level Working Group (TSLWG) is a technical working group of ICSM, with representation from national, state, port and scientific agencies engaged in the determination of tides and sea level.  The agencies represented include the Australian Hydrographic Office, the National Tidal Centre, the Bureau of Meteorology, the Australian Antarctic Division, the Australian Academy of Science, the Association of Australian Ports and Marine Authorities, state marine agencies and port authorities.

The role of the TMSLWG is to:

  • co-ordinate a national database of tidal records.
  • develop national standards and best practice guidelines for tidal related matters.
  • acts as a focal point for national enquiries relating to tides and mean sea level.

Australian Coastal Vertical Datum Transformation (AusCoastVDT) Software

AusCoastVDT is an easy to use vertical datum transformation tool, developed in collaboration with the CRCSI, applicable to the Australian coast. The tool includes transformations between data referenced to the GRS80 ellipsoid (GDA94) ⁄ WGS84 ellipsoid (WGS84), Lowest Astronomical Tide (LAT), Mean Sea Level (MSL), the Australian Height Datum (AHD), Highest Astronomical Tide (HAT) and other tidal vertical datums of user interest (and vice versa). The tool was developed in 2013 and updated in 2016, with the supplied vertical separation grid based on the limited data available at the time. The grid will be updated as new information becomes available. The tool also offers the option for users to supply their own vertical separation grid.

Installation instructions are available in a read me text file and the user manual is installed with the software and can be accessed via the ‘Help’ button on the ‘About’ tab. 

This application is no longer supported (Since Sep 2019) for data updates. It does not contain the latest tidal surfaces (including MSL above chart datum) or AUSGEOID 2020. A new version of the tool with updated data is currently being investigated with the assistance of AUSSEABED.

Download the AusCoastVDT tool version 1.21 — Transformation grid updated September 2019.

The Australian Tides Manual

The TMSLWG prepared and periodically updates a manual for tides in the Australian context. It was published in 2004 as the Australian Tides Manual. (SP9) This was originally published by the National Mapping Council in 1984 as the booklet Recommended Operating Procedures for Tide Gauges on the National Network; Special Publication 9 (or SP9).

The Manual has been expanded and up–dated and is now available in .PDF format.

Australian Tides Manual V6.0 updated June 2021

Accuracy of Tidal Predictions

An assessment of the factors which contributing to confidence in the accuracy of tidal predictions can be accessed here.


Current Activities of TMSLWG

The groups current activities include:

  • Developing an Australian Tidal Data exchange format to assist in data exchange between agencies and users.
  • Standardising tidal analysis methods to provide for improved tidal predictions for safe navigation of large vessels.
  • Investigation of mean sea levels around Australia and their significance for land-based vertical datums.

Web Sites of Interest

Tidal Interface Working Group (TIWG)

In November 2006, ICSM disbanded its Tidal Interface Working Group (TIWG).  This had developed a Compendium of Terms Associated with the Tidal Interface Zone.  Activities relating to the tidal interface zone will primarily be undertaken by the PCTMSL.

For Further Information:

Secretary TSLWG (Rebecca Cusack)
Locked Bag 8801
Wollongong, NSW 2500
Phone: 02 4286 9575
Group Mailbox: