Scoping study and ‘gap’ analysis for the development of a national hydroid model – “AusHydroid”

The Challenge

Australia’s land and sea vertical datums have traditionally been treated separately, so are not well connected across the coastal boundary. Subsequently, many local chart datums (CDs) are not accurately located within an Earth-centred reference frame. This project comprises a scoping study and ‘gap’ analysis to determine the requirements and challenges for establishing a model of the vertical separation between a defined global, Earth-centred reference frame and local maritime CDs. This proposed model is referred to as AusHydroid and would allow GNSS-observed ellipsoidal water level heights related to the GRS80 ellipsoid (used by the Geocentric Datum of Australia 2020 (GDA2020)) to be transformed into local chart heights which comprise the National Chart Datum.


The project partners were Curtin University, Department of Defence, Geoscience Australia, Bureau of Meteorology and WA Department of Transport.

The Solution

AusHydroid will be a consistent reference system that can transform multiple reference surfaces (e.g., GDA2020, mean sea level, lowest astronomical tide) across the coastal boundary and in offshore shelf regions, also providing an associated uncertainty on the transformed value to the user. The aim of this scoping study is to develop methods and test available data sets, datums and reference frames that can be used for the development of an AusHydroid model, identifying additional targeted observations. Specifically, the aims of this project were to:

  1. Identify available pertinent ocean and land data sets.
  2. Evaluate the available data for their suitability and quality.
  3. Determine additional data acquisition requirements.
  4. Develop and test methods for combining data sets onto a common vertical reference.

Aim 1 was conducted for the full Australian coastline, while Aims 2-4 were limited to specific test area/s, depending on stakeholder requirements and the timeline for the proposed work packages. To ensure the deliverables are of use to the Intergovernmental Committee on Survey and Mapping (ICSM) AusHydroid working group and other Stakeholders, this project used the Agile methodology.

The work packages were:

  1. Audit of National and International Data sets, and existing/ongoing programs.
  2. Evaluate Available Data sets.
  3. Investigate Methods to Combine Heterogeneous Observations.
  4. Make Recommendations for the Next Step Towards a National AusHydroid.

ICSM instigated the AusHydroid Working Group in 2018 to commenced development of the business processes, use cases, define minimum standards and specifications for the data and models to improve the determination of the vertical datum separation. The development of AusHydroid addressed coastal datum inconsistencies which are a priority for the ICSM and the Australian Government HydroScheme Industry Partnership Program (HIPP). The benefits of an accurate AusHydroid will be realised as more efficient and safer maritime navigation, offshore oil and gas production and improved knowledge of coastal inundation risks associated with sea level rise, together with tide surges.

Download the Scoping Study and ‘GAP’ Analysis for the Development of a National Hydroid Model (“AusHydroid”)


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