<div>The Abbot Point to Hydrographers Passage bathymetry survey was acquired for the Australian Hydrographic Office (AHO) onboard the RV Escape during the period 6 Oct 2020 – 16 Mar 2021. This was a contracted survey conducted for the Australian Hydrographic Office by iXblue Pty Ltd as part of the Hydroscheme Industry Partnership Program. The survey area encompases a section of Two-Way Route from Abbot Point through Hydrographers Passage QLD. Bathymetry data was acquired using a Kongsberg EM 2040, and processed using QPS QINSy. The dataset was then exported as a 30m resolution, 32 bit floating point GeoTIFF grid of the survey area.</div><div>This dataset is not to be used for navigational purposes.</div>

Map is an image of the seafloor and land topograhpy with the seafloor data between latitudes 64 degrees North and 72 degrees South by Smith and Sandwell (1997) with more information from W.H.F Smith and D.T. Sandwell, Global Seafloor Topography from Satellite Altimetry and Ship Depth Soundings, Science, v.277, p. 1956-1962, 26 September 1997. This has been combined with land topography from the Global Land One-km Base Elevation (GLOBE) Project. This image has been modified in ER Mapper to increase the depth perception by chaning the sun angle.

Geoscience Australia and the National Oceans Office carried out a joint venture project to produce a consistent, high-quality 9 arc second (0.0025° or ~250m at the equator) bathymetric data grid of those parts of the Australian water column jurisdiction lying between 92° E - 172° E and 8° S - 60° S. This is an article for the PREVIEW magazine.

This document will be posted on the GA and CSIRO-Marine websites. Dr. Neville Exon was Chief Scientist and Cruise Leader for this survey.

Legacy product - no abstract available

The RV Franklin sailed from Brisbane on 17th January 2002 and returned to Cairns on 9th February, 2002. The cruise discovered that a zone of strong tidal currents at the northern end of the Great Barrier Reef prevents the southward advance of sediment that would otherwise bury the coral reefs. The Fly River, located in close proximity to the northern end of the Great Barrier Reef, discharges about 120 million tonnes/yr of sediment. This sediment does not penetrate as far south into the reef area as might be expected because, over glacial-interglacial cycles of sea level change, the southward-prograding deposits are eroded by tidal currents. Deployment of an instrumented current meter and suspended sediment measurement frame on the seabed, offshore from the Fly River Delta, recorded a net sediment advection southwards. Sediment transport was greatest following a northerly wind event, which caused high bottom stress and increased turbidity levels. Swath sonar mapping and underwater video equipment were used to map a series of channels up to 220 m deep extending from eastern Torres Strait across the northern end of the Great Barrier Reef. Channels in the north are clearly relict fluvial channels, exhibiting lateral accretion surfaces and incised channels that intersect and truncate underlying strata. Over-deepened channels in the south, however, appear to have formed by tidal current scour. They exhibit closed bathymetric contours at both ends and are floored with well-sorted carbonate gravely sand. Oceanographic observations indicate that the channels provide a conduit onto the shelf for up-welled Coral Sea water. The deepest channels form isolated depressions, and possibly were the sites of lakes during the last ice age. Preliminary modelling indicates that the strongest tidal currents occur when sea level is about 40m below present, suggesting that the channels are Pleistocene or older in age and of relict origin.

Acoustic backscatter from the seafloor is a complex function of signal frequency, seabed roughness, grain size distribution, benthos, bioturbation, volume reverberation and other factors. Angular response is the variation in acoustic backscatter with incident angle and it is considered be an intrinsic property of the seabed. The objective of the study was to illustrate how the combination of a self-organising map (SOM) and hierarchical clustering can be used to develop an angular response facies map for Point Cloates, northwest Australia; demonstrate the cluster visualisation properties of the technique; and highlight how the technique can be used to investigate environmental variables that influence angular response.

Legacy product - no abstract available

Please note: This product has been superseded by 50m Multibeam Dataset of Australia 2018. - This tile contains all multibeam data held by Geoscience Australia on August 2012 within the specified area. The data has been gridded to 50m resolution. Some deeper data has also been interpolated within the mapped area. The image provided can be viewed on the free software CARIS Easyview, available from the CARIS website: www.caris.com under Free Downloads.

Legacy product - no abstract available