Darwin Port Corporation
Darwin is a key port on Australia’s North Coast that supports not only the sea freight requirements of the growing Northern Territory, but is also becoming a major hub for the export of Liquefied Natural Gas and other resources. A key facet of iXblue’s operations has been high accuracy survey in complex Port Environments. iXblue has undertaken multiple surveys in the Port of Darwin since 2010, for the Darwin Port Corporation, the Royal Australian Navy; and as part of a cooperative program involving the Northern Territory Government, the Australian Institute of Marine Science and Geoscience Australia.
Whilst Darwin Harbour is naturally deep for much of the navigable areas, there are several critical areas where large ship movements are restricted by the available tide and many areas critical to small ship operations either dry at very low tides, or are not navigable. In consultation with the Government stakeholders, a survey specification closely aligned with the IHO S44 Order 1a was agreed for the project.
The harbour and surrounding waterways include extensive environmentally sensitive mangroves. A large tidal range and large areas of very shallow water demanded great care during the course of the survey. It was discovered early on in the project that the risk of touching the bottom with a sensitive and expensive sonar array was high.
Surveys undertaken in Darwin have included the use of Kongsberg EM3002D and R2Sonic 2024 MBES systems, with the majority of Darwin Harbour mapped over the course of multiple surveys. Surveys have included the mapping of not only the deep and navigable shallow areas, but also much of the extensive shallow waterways and inter-tidal areas. The area is complex with a large tide range (greater than 8m), and as a part of the survey program the GPS Ellipsoid relationship to survey datum has been mapped across much of the harbour, using a GPS Tide Buoy to accurately determine the relationship between survey datum and the GPS Ellipsoid.
Over a two year project period, a large percentage of the Darwin Harbour and surrounds were surveyed to IHO Order 1a standard or higher. The deployment of the GNSS tide buoy has increased the knowledge of the Geoid Spheroid model for the area and proven that this survey methodology is an option for future surveys requiring high order accuracies and wishing to use GNSS technology for bathymetric heighting. The dataset has also provided many environmental stakeholders a valuable tool with which to increase the understanding of the Darwin Harbour and surrounds.