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The Creation of High Resolution Bathymetry Grids for the Lord Howe Island Region

Note: This metadata describes the dataset in accordance with the ANZLIC (Australia New Zealand Land Information Council) Core Metadata Guidelines Version 2.


Dataset citation

ANZLIC unique identifier: ANZCW0703013935

Title: The Creation of High Resolution Bathymetry Grids for the Lord Howe Island Region


Custodian

Custodian: Geoscience Australia

Jurisdiction: New South Wales


Description

Abstract:

Detailed seabed bathymetric data are needed to better understand our marine environment because models of seabed morphology derived from these data provide useful insights into physical processes that act on the seabed and the location of different types of seabed habitats. Lord Howe Island lies approximately 450 km off the northern coast of New South Wales. It is a volcanic island with a fringing coral reef on its western shore, and a shallow (20 - 120 m) shelf surrounds the island. Bathymetry data are required in this area to help identify major seabed processes and habitats, especially relict reef structures, and to measure how well physical seabed properties act as surrogates of patterns of biodiversity on this mid-ocean carbonate shelf. The data are also required to enable modelling of tsunami as they interact with the shelf around the island and the coast.

Four new bathymetry grids have been created, including grids that integrate bathymetry with the island's topography.

ANZLIC search words:

  • GEOSCIENCES Geomorphology
  • GEOSCIENCES Geophysics
  • MARINE
  • MARINE Reefs
  • OCEANOGRAPHY Physical

Spatial domain:

locality map

Geographic extent name: TASMAN SEA - TASMAN SEA - Ocean and Sea Regions - Australia

Geographic extent polygon: 158.15 -30.65, 160.35 -30.65, 160.35 -32.85, 158.15 -32.85, 158.15 -30.65,

Note: The format for each Geographic extent name is: Name - Identifier - Category - Jurisdiction (as appropriate) See GEN Register

Geographic bounding box:
North bounding latitude: -30.65 °
South bounding latitude: -32.85 °
East bounding longitude: 160.35 °
West bounding longitude: 158.15 °

Data currency

Beginning date: 2009-07-01

Ending date: 2010-06-30


Dataset status

Progress: Complete

Maintenance and update frequency: Not Known


Access

Stored data format:
DIGITAL - ers ER Mapper raster dataset ER Mapper Geographic WGS84
DIGITAL - XYZ ascii XYZ ascii grid ArcGIS Geographic WGS84
Available format type:
DIGITAL - XYZ ascii XYZ ascii grid ArcGIS Geographic WGS84
DIGITAL - ers ER Mapper raster dataset ER Mapper Geographic WGS84

Access constraints:

Only the 250 m grid is available for public release.

Free Data Download

Data quality

Lineage:

The grids are derived from data in Geoscience Australia databases and recent sources which will eventually be entered into those databases. Satellite derived bathymetry was used in shallow waters. Seven swath datasets acquired between 1992 and 2009 were used. Five of the surveys supply extensive regional coverage, whilst the others are basically multibeam transits of the area. One LADS survey from the AHS was used. A high quality coastline, as well as topography data of Lord Howe and its islands were obtained from the Land and Property Information Management Authority. Eleven singlebeam surveys from the GA MARDAT database. These data range in vintage from 1971 to 1998 and were edited to remove suspect datapoints, but were left uncorrected with regards speed of sound issues. Chart data from the AHS was used in both deep and shallow water but most of it was superseded by swath data. ETOPO1 data was used in the area of two seamounts where data were sparse. One singlebeam survey fro the University of Wollongong that was previously unknown to GA was used.

Positional accuracy:

The grid incorporates data from surveys acquired since 1959. Modern surveys which used GPS have a positional accuracy of 5 - 30 m depending on several factors, while earlier surveys which used dead reckoning and Transit satellite fixes had positions accurate to 50- 2000 m depending upon the water depth and strength of currents. These surveys overlap in an irregular distribution and the more extensive, higher quality swath datasets were used to mask data of lower quality and extent. Effectively there are two regions in the grid. One covered by multibeam data of high positional and bathymetric accuracy and the other heavily reliant on chart data and singlebeam surveys which are of lower positional and bathymetric accuracy. The grid cell sizes are 0.00225 deg (nominal 250m), 0.0009 deg (nominal 100m), 0.00036 deg (nominal 40m) and 0.000072 deg (nominal 8m).

Attribute accuracy:

The attribute accuracy varies depending upon the predominant data source in an area. Where modern, high quality swath bathymetric data that form an areal coverage exists, overlapping swaths and speed of sound corrections show that the data are quite accurate. Some transit swath data also have speed of sound corrections applied and are assumed to be highly accurate. Other transit swath surveys have utilized a nominal speed of sound of 1500 m/s and are not as accurate (problems were encountered trying to apply correction). Most other data assume a nominal speed of sound of 1500 m/s, although some have had corrections applied. For a significant portion of the region, predicted bathymetry from satellite data are the only source of data. No attempts have been made to compare bathymetry from high quality datasets to that which would be obtained from lesser data sets, although all the data exist to perform such a task.

Logical Consistency:

Each of the input datasets was examined in detail and edited where necessary. Areas of poor navigation and obviously bad bathymetry were discarded. A hierarchical system was employed whereby the best and most extensive datasets replaced data of lesser datasets. All the various datasets were then brought together by the gridding algorithm (Intrepid - Desmond Fitzgerald Associates) and an ERMapper format grid produced.

Completeness:

All of the known, available data (to 2010) were used in the production of the grids. The GA databases which underpin this grid will be updated as new surveys are completed and older surveys have corrections applied to them. A data density map was produced as a means of assessing the completeness of coverage and it could possibly be used as a variably opaque overlay of the bathymetric grid to highlight good quality areas and darken lesser quality areas.


Contact information

Contact organisation: Commonwealth of Australia (Geoscience Australia) (GA)
Contact position: Manager Client Services
Mail address: Cnr Jerrabomberra Ave and Hindmarsh Dr
Mail address: GPO Box 378
Locality: Canberra
State: ACT
Country: Australia
Postcode: 2601
Telephone: 02 6249 9966
Facsimile: 02 6249 9960
Electronic mail address: sales@ga.gov.au

Metadata information

Metadata date: 2013-03-08


Additional metadata

Metadata reference XHTML: http://www.ga.gov.au/meta/ANZCW0703013935.html

Metadata reference XML: http://www.ga.gov.au/meta/ANZCW0703013935.xml

Mleczko, R., Sagar, S., Spinoccia, M., and Brooke, B. 2010. The Creation of High Resolution Bathymetry Grids for the Lord Howe Island Region. Geoscience Australia Record 2010/36.

Authors:Mleczko, R. Sagar, S. Spinoccia, M. Brooke, B.
SPATIAL INFORMATION FOR THE NATION