Outer Darwin Harbour Marine Survey 2015: High resolution bathymetry grid

Brief description

This resource contains bathymetry data for Outer Darwin Harbour collected by Geoscience Australia (GA), the Australian Institute of Marine Science (AIMS) and the Northern Territory Government (Department of Land Resource Management) during the period from 28 May and 23 June 2015 on the RV Solander (survey SOL6187/GA0351). This project was made possible through offset funds provided by INPEX-led Ichthys LNG Project to Northern Territory Government Department of Land Resource Management, and co-investment from Geoscience Australia and Australian Institute of Marine Science. The intent of this four year (2014-2018) program is to improve knowledge of the marine environments in the Darwin and Bynoe Harbour regions by collating and collecting baseline data that enable the creation of thematic habitat maps that underpin marine resource management decisions. The specific objectives of the survey were to: 1. Obtain high resolution geophysical (bathymetry) data for outer Darwin Harbour, including Shoal Bay; 2. Characterise substrates (acoustic backscatter properties, grainsize, sediment chemistry) for outer Darwin Harbour, including Shoal Bay; and 3. Collect tidal data for the survey area. Data acquired during the survey included: multibeam sonar bathymetry and acoustic backscatter; physical samples of seabed sediments, underwater photography and video of grab sample locations and oceanographic information including tidal data and sound velocity profiles. This dataset comprises multibeam bathymetry surface grid. A detailed account of the survey is provided in: Siwabessy, P.J.W., Smit, N., Atkinson, I., Dando, N., Harries, S., Howard, F.J.F., Li, J., Nicholas, W.A., Potter, A., Radke, L.C., Tran, M., Williams, D. and Whiteway, T., 2015. Outer Darwin Harbour Marine Survey 2015: GA0351/SOL6187 Post-survey report. Record 2016/008. Geoscience Australia, Canberra. http://dx.doi.org/10.11636/Record.2016.008

This dataset is not to be used for navigational purposes.

Lineage

Maintenance and Update Frequency: asNeeded

Statement: The Outer Darwin Harbour Marine Survey 2015, GA-0351 SOL6187 was acquired by Geoscience Australia (GA) in collaboration with the Australian Institute of Marine Science (AIMS) and Department of Land Resource Management (Northern Territory Government) onboard the RV Solander between 28 May and 23 June 2015.
The AIMS Cruise Leader was Mr. David Williams, the NTGov Chief Investigator onboard was Dr. Neil Smit, and the GA Survey Leader was Dr. Justy Siwabessy.
This dataset was acquired and processed onboard and in the office by Justy Siwabessy using CARIS HIPS & SIPS ver 8.1.13.

Processing:
1. First a vessel configuration file was created where the co-ordinates of the motion sensor and DGPS antenna and patch test offsets were recorded.
2. A new project was then created and the vessel configuration file was attached to the project file.
3. The raw swath sonar data, in raw.all format, for each line was then imported into the project and the vessel information assigned to the data.
4. The motion sensor, DGPS and heading data were then cleaned using a filter that averaged adjacent data to remove artefacts.
5. Different sound velocity profiles data for each block were attached to the corresponding raw swath sonar data files to correct the depths for changes in the speed of sound through the water column.
6. Then a new blank field area was defined that specified the geographic area of study and the co-ordinate system used. The co-ordinates for the study areas were WGS84 UTM-52S.
7. The data was cleaned by applying several filters including surface filters to remove spikes in the data. A manual inspection of the data was undertaken as required using Subset Editor module in Caris HIPS/SIPS software.
8. All the data for each bathymetric, motion sensor, DGPS, heading, tide and sound velocity profile data were merged to produce the final processed data file. A weighted grid of the processed data was then created for each Block.
In GA, the tide was applied to the grid to correct for tidal variations and velocity corrections were performed to correct for different artefacts and mismatches.
9. The processed data was finally exported as grids in the optimum resolution the data can provide with reference to EGM2008 vertical datum (~ mean sea level).

Metadata:
The multibeam bathymetry was acquired by the following survey:
- Survey Name: Outer Darwin Harbour Marine Survey 2015 (GA-0351/SOL6187)
- Vessel Name: RV Solander
- Institutions: Geoscience Australia, AIMS, NTGov
- Country: Australia
- Operator: AIMS
- Multibeam system: Kongsberg EM2040C (dual)
- Year of installation: 2014
- Nominal sonar frequency: 300 kHz
- Number of beams: 800 beams
- Beamwidth across track: 1.3 degrees
- Beamwidth along track: 1.3 degrees
- Pulse length: variable
- Selectable depth range: 10 m - 50 m
- Vessel speed: 7 - 10 knots
- Start Date: 28/05/2015
- End Date: 23/06/2015
- Start Port: Darwin
- End Port: Darwin
- Grid resolution: 1 m
- Number of grids: 1
- Total surface coverage: 713.31 km2
- Vertical Datum: MSL
- Horizontal Datum: WGS84 UTM-52S
- Use Limitation: This dataset is not to be used for navigational purposes.