Seafloor Mapping Survey, Windmill
Islands and Casey region, Antarctica
GA-0348 Post Survey Report, December 2014 - February 2015
GEOSCIENCE AUSTRALIA
RECORD 2016/03
Carson, C. J.1, Forrest, D.2, Walker, G.3, the Deployable Geospatial Support Team3, Post, A.1,
Smith, J.1, Bartley, R.4 and Tracey, P.4
1.
2.
3.
4.
Geoscience Australia
IXSurvey Australia
Royal Australian Navy
Australian Antarctic Division
Department of Industry, Innovation and Science
Minister for Resources, Energy and Northern Australia: The Hon Josh Frydenberg MP
Assistant Minister for Science: The Hon Karen Andrews MP
Secretary: Ms Glenys Beauchamp PSM
Geoscience Australia
Chief Executive Officer: Dr Chris Pigram
This paper is published with the permission of the CEO, Geoscience Australia
© Commonwealth of Australia (Geoscience Australia) 2016
With the exception of the Commonwealth Coat of Arms and where otherwise noted, this product is
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ISSN 2201-702X (PDF)
ISBN 978-1-925124-96-5 (PDF)
GeoCat 87790
Bibliographic reference: Carson, C.J., Forrest, D., Walker, G., Deployable Geospatial Support
Team, Post, A., Smith, J., Bartley, R. & Tracey, P. 2016. Seafloor Mapping Survey, Windmill Islands
and Casey region, Antarctica: GA-0348 Post Survey Report, December 2014 - February 2015. Record
2016/03. Geoscience Australia, Canberra. http://dx.doi.org/10.11636/Record.2016.003
Contents
1 Executive summary ...............................................................................................................................1
2 Survey overview ....................................................................................................................................2
2.1 Regional setting ...............................................................................................................................2
2.2 Personnel .........................................................................................................................................3
2.3 Survey objectives .............................................................................................................................3
2.3.1 Objectives ...................................................................................................................................3
2.3.2 Priority areas ..............................................................................................................................4
2.3.3 Access to Datasets .....................................................................................................................7
3 Methodology ..........................................................................................................................................8
3.1 Multibeam system ............................................................................................................................8
3.2 Survey platform and survey operating parameters ..........................................................................8
3.3 Motion referencing unit and satellite positioning ..............................................................................8
3.4 Seafloor imagery and sampling .....................................................................................................10
3.5 Macroalgae spectral analysis.........................................................................................................13
3.6 Survey log ......................................................................................................................................15
4 Preliminary interpretation of seafloor features.....................................................................................17
4.1 Bedrock ‘highs’ ...............................................................................................................................18
4.2 Channels ........................................................................................................................................18
4.3 Glacial submarine landforms .........................................................................................................19
4.4 Basins ............................................................................................................................................20
5 Concluding remarks.............................................................................................................................21
6 Acknowledgements .............................................................................................................................22
References .............................................................................................................................................23
Vessel calibrations and operational parameters .................................................................24
A.1 Motion sensor performance and vessel offsets .............................................................................24
A.1.1 Offset summary........................................................................................................................24
A.2 Multibeam echosounder (MBES) patch tests ................................................................................25
A.2.1 Methodology ............................................................................................................................26
A.2.2 Environmental conditions .........................................................................................................27
A.2.3 Results .....................................................................................................................................27
A.2.4 CARIS™ offsets .......................................................................................................................27
A.3 Vessel draft gross error check .......................................................................................................28
A.4 Squat trial data ..............................................................................................................................28
A.4.1 Methodology ............................................................................................................................28
A.4.2 Results .....................................................................................................................................28
A.5 Bar check .......................................................................................................................................29
A.5.1 Methodology ............................................................................................................................29
A.5.2 Preliminary results ...................................................................................................................29
A.5.3 Processed results ....................................................................................................................29
A.6 Equipment defects and issues ......................................................................................................29
A.6.1 Kongsberg EM3002 starboard transducer ...............................................................................29
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
iii
A.6.2 Uninterruptible power supply (UPS) ........................................................................................31
A.6.3 240 volt petrol generators ........................................................................................................31
A.6.4 SIS acquisition software...........................................................................................................32
A.7 Operational settings and parameters ............................................................................................32
A.7.1 Geodetic control .......................................................................................................................32
A.7.2 Vessel draft and squat corrections ..........................................................................................32
A.7.3 Backscatter ..............................................................................................................................33
A.7.4 Tides & sounding datum ..........................................................................................................33
Sample, video/camera and sound velocity profile locations ...............................................37
B.1.1 Sampling ..................................................................................................................................37
B.1.2 Sound velocity sensor and profile locations .............................................................................39
Acronyms used in report .....................................................................................................42
iv
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
1 Executive summary
Geoscience Australia (GA) is the national geoscience agency that provides geoscientific advice to the
Australian Government to support national priorities for Australia and its external territories.
Underpinning that advice, GA conducts a diverse range of earth science research and monitoring
activities, provides geoscience products and services that address national issues and contributes to
the evidence base for informed policy development and decision-making.
Geoscience Australia’s strategic objective, ‘Managing Australia’s Marine Jurisdictions’, supports the
provision of marine geoscience information and advice on the marine jurisdiction adjacent to the
Australian Antarctic Territory (AAT). This information underpins Australia’s Antarctic strategic interests
and obligations under the Antarctic Treaty System (ATS), associated environmental protocols and
provides fundamental evidence supporting domestic Antarctic legislation (e.g. Antarctic Treaty
[Environment Protection] Act 1980, and the Antarctic Marine Living Resources Conservation Act 1981)
Seafloor mapping provides the necessary information to enable informed marine environmental
management and for minimising risk for maritime operations and navigation. Accurate seafloor maps
are particularly important for sustainable management of high-use, near-shore areas adjacent to
Australia’s research stations in the Australian Antarctic Territory (AAT). The shallow water marine
environment around Casey is a high use area and is frequently visited by the RSV Aurora Australis
and smaller vessels conducting scientific research in the area, highlighting the need for accurate high
resolution bathymetric data.
From December 2014 to February 2015, Geoscience Australia conducted a multibeam sonar survey
(GA-0348) of the coastal waters around Casey station and the adjacent Windmill Islands. The survey
utilised GA’s Kongsberg EM3002D multibeam echosounder, motion reference unit and C-Nav
differential GPS system mounted on the Australian Antarctic Division’s (AAD) science workboat the
Howard Burton. The survey was a collaborative project between GA, the AAD and the Royal
Australian Navy (RAN).
During the survey a total of ~27.3 km2 of multibeam bathymetry, backscatter and water-column data
were collected, extending coverage of a RAN multibeam survey (survey number HI545) conducted the
previous season (~7 km2). The regions covered extended seaward of Newcomb Bay and Clark
Peninsula northwest of Casey Station, and seaward of Shirley and Beall Islands to the southwest.
Complimentary datasets were also collected, including 18 drop video deployments to assess the
benthic ecosystem composition and 39 sediment samples to ground-truth the seafloor substrate.
Macroalgae spectral analyses were also collected to develop a spectral library for possible future
satellite bathymetry investigations.
The new high-resolution bathymetric grid (1 m resolution) reveals seafloor features in the Casey area
in unprecedented detail. This data will be used for developing a seafloor geomorphological map,
improving the regional navigational charts (RAN) and, in conjunction with supplementary datasets,
developing informed environmental management protocols for this high use region.
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
1
2 Survey overview
The Casey shallow-water near-shore seafloor mapping survey (GA-0348) was conducted as
collaboration between Geoscience Australia (GA, Department of Industry and Science), the Royal
Australian Navy (RAN, Department of Defence) and the Australian Antarctic Division (AAD,
Department of the Environment). The survey was conducted as part of the ongoing AAD program
Hydrographic Surveying and Bathymetric Data Acquisition (AAD project 3326) and complements a
previous charting survey to the Casey region undertaken by RAN and AAD (using the RAN vessel
ASV Wyatt Earp) in 2013/14 (also conducted under AAD 3326).
The purpose of the survey was to acquire geophysical, geological and biological data from the
seafloor environment in the shallow (<250 m) coastal waters adjacent to Casey station. The survey
acquisition phase formed the main work program for the Antarctic Geoscience Program and Advice
activity as part of the Marine and Antarctic Geoscience (MAG) Section at Geoscience Australia during
2014/15.
The shallow water marine environment around Casey station, East Antarctica, is a high use area in
the Australian Antarctic Territory, and is frequently visited by the RSV Aurora Australis and smaller
vessels conducting scientific research in the area, yet bathymetry data in the area is limited.
Additionally, a long-term dive program has revealed the marine habitats in the area host globally
significant levels of biodiversity, but this knowledge is geographically restricted in scope (i.e. shallow
depths, close to shore). This biodiversity faces pressures from human activities and climate change,
yet extensive knowledge gaps remain, limiting efforts to conserve and manage it effectively.
This survey report is sourced, adapted and modified from the contractor (IXSurvey) report, authored
by Dean Forrest, submitted to Geoscience Australia on 24 February 2015 at the completion of the
survey (IXSurvey report reference AU335). Unabridged contractor reports, containing detailed
technical settings, calibrations and GNSS checks are available on request from Geoscience Australia.
2.1 Regional setting
Australia’s research station, Casey, is located on Bailey Peninsula, overlooking Vincennes Bay,
Wilkes Land. The area surveyed during the course of this survey lies approximately between latitudes
66-66.5° S and longitudes 110-111° E. The coastal area is characterised by numerous small bays,
inlets channels and offshore islands (collectively known as the Windmill Islands). Casey is occupied
year round with a summer population of approximately 90-100 personnel and wintering population of
approximately 20 people.
Existing hydrographic charts of the region (Chart number Aus601 Approaches to Casey 1:50,000 with
inset at 1:12,500 of Newcomb Bay, 1994) were developed by the Australian Hydrographic Office
(AHO)-Royal Australian Navy (RAN) on the ASV Wyatt Earp workboat using single beam techniques
during the early 1990’s.
2
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
2.2 Personnel
The following personnel were involved in the survey either during technical preparation, during sea
trials at Kettering (Tasmania) or participation on the primary survey at Casey station.
Geoscience Australia:

Chris Carson (Science leader).

Ian Atkinson (Multibeam system engineer – Australia-based operations).

Nick Dando (Multibeam system engineer – Australia-based operations).
IX Survey:

Dean Forrest (GA contracted hydrographic surveyor).
Royal Australian Navy – Deployable Geospatial Support Team (DGST):

Lieutenant-Commander Geoffrey Walker (RAN Officer in Charge).

Lieutenant-Commander Mark Matthews (RAN contracted hydrographic surveyor) ― returned to
Australia 22 Dec 2014, prior to commencement of on-water surveying.

Leading Seaman Hydrographic Survey Officer Hannah Lee (Hydrographic Coxswain).

Able Seaman Hydrographic Survey Officer Glen Cooksey (Hydrographic Coxswain).
2.3 Survey objectives
2.3.1 Objectives
This survey (GA-0348) was conducted under AAD Project 3326 (Hydrographic Surveying and
Bathymetric Data Acquisition), a multiyear program to improve the bathymetric datasets in the nearshore regions immediately adjacent to Australian research stations (see also O'Brien, 2010). The
primary objectives of the survey were to:

Collect multibeam sonar bathymetry of the near-shore region around the Windmill Islands to
improve understanding of the morphology of the seafloor and to update navigational charts of the
region.

Collect backscatter and water column acoustic data for seafloor substrate information and
macroalgae distribution respectively.

Collect sediment samples to ground truth acoustic backscatter data.

Collect benthic video imagery to facilitate understanding of the relationship between benthic
ecosystems and the physical environment.

Collect visible light spectral signatures from macroalgae to facilitate shallow-water satellite derived
bathymetry for future work programs.
Geoscience Australia provided a dual-head Kongsberg EM3002 multibeam sonar unit, and ancillary
navigational and motion reference equipment (see section 3 for further details). Geoscience Australia
funded an external contractor from IXSurvey for operation of the multibeam unit (with the Kongsberg
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
3
propriety software Seafloor Information System, or SIS), ancillary equipment (including pre-survey
bench tests and sea trials) and for processing bathymetric data during the survey. Geoscience
Australia also provided sediment sampling equipment and operational support through the
Observations and Science Support Group.
The AAD provided essential logistics support in Australia and at Casey station, provision and
preparation of the vessel for survey operations and accommodation for survey staff.
The backscatter and water column data was collected but has not been processed at the time of
publication.
2.3.2 Priority areas
During pre-survey discussions with AAD and RAN, the survey area was divided into nine priority areas
(Table 2.1, Figure 2.1) for multibeam mapping and sampling. These priority areas were determined
and agreed upon to meet the requirements of all survey partners and were based on the following
criteria:

Existing data (collected during the RAN multibeam survey in 2013/14, survey number HI545).

Areas of scientific interest, including areas adjacent to Antarctic Specially Protected Areas
(ASPAs) and areas frequented by the AAD dive program.

Shiptracks of the RV Aurora Australis and other vessels, which identify areas of high-use for
shipping approaches to Casey anchorage and require accurate charting.

Regional small boat operations.

Uncharted areas.
4
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
Figure 2.1 Priority areas (1-9) as discussed in text. The grey area shows the combined coverage obtained by the
2013/14 RAN survey (HI545) and the GA-RAN-AAD 2014/15 survey (GA-0348). Bathymetric contours as shown
are based on existing chart contours (chart Aus601).
The total area of the priority areas is approximately 289 km2, ranging in depth from the intertidal zone
to ~250 m. Some regions were complex and challenging to survey, with numerous shoals, reefs and
inlets, whereas other regions were open expanses of water. The survey priority areas represent a
multiyear strategic perspective and were developed for planning purposes. Daily survey operations
were largely dictated by weather and logistics. Details of the individual areas are outlined in Table 2.1.
Table 2.1 The nine priority areas as discussed in text, (refer to Appendix C for acronyms).
Priority
area
Area (km2)
1
Location
Comments
11
Newcomb Bay
Charting and science objectives, complete surveying
from 2013/14 season
2
11
O’Brien Bay
Charting and science objectives, complete surveying
from 2013/14 season
3
38
Seaward of Newcomb Bay
Charting and science objectives
4
32
Cronk Islands
Uncharted areas, science objectives
5
46
Offshore between Casey
and Frazier Islands
Charting and science objectives
6
30
Sparkes Bay
Uncharted, ASPA 103, science objectives
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
5
Priority
area
Area (km2)
7
Location
Comments
57
Frazier Islands
Charting and ship approaches to ASPA 160
8
29
Swain Group
Uncharted waters
9
35
Donovan Islands
Charting and science objectives
In total, survey GA-0348 completed 27.3 km 2 of area (Figure 2.2) ranging from the intertidal zone
(roughly 1 m) to 161 m of water depth, adding to the 7.0 km 2 coverage by the RAN-AAD survey
(HI545) collected during 2013/14.
Figure 2.3 shows the combined coverage of both surveys covering an area of 34.3 km2. Initial priority
was given to completing areas 1 and 2 (complete coverage not possible due to fast ice close to the
shore and in narrow channels preventing vessel access) following on from the previous season
(2013/14) by the RAN on the ASV Wyatt Earp. This also served the purpose of gaining expertise
amongst the survey team on the boat, equipment and appraising the local weather and environmental
variables before surveying more remote regions further afield.
Figure 2.2 Multibeam coverage conducted by survey GA-0348 during Dec 2014 to Feb 2015, representing a total
of 27.3 km2. The small ‘unconnected’ areas of survey in Newcomb Bay are ‘in-fill’ areas, expanding onthe RANAAD coverage from 2013/14 season. Bathymetry contours and priority areas as shown in Figure 2.1 are not
shown for clarity.
6
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
Figure 2.3 The combined multibeam coverage from RAN-AAD survey conducted in 2013/14 (7.0 km2, HI545) and
GA-RAN-AAD (27.3 km2, GA-0348) conducted in 2014/15 (27.3 km2) with main geographic features labelled.
2.3.3 Access to Datasets
The multibeam bathymetry data collected on this survey can be sourced at Geoscience Australia under
GeoCat number 83224, entitled ‘Casey Station (Antarctica) Bathymetry Survey, GA-0348 / AAD 3326’.
Seafloor imagery (video and stills) collected during the survey can be sourced at Geoscience Australia
under GeoCat 83876, entitled ‘Casey Seafloor Imagery’. Copies of the bathymetry datasets may also be
obtained at the Australian Antarctic Data Centre on the Australian Antarctic Division web site.
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
7
3 Methodology
3.1 Multibeam system
Bathymetric data was acquired using Geoscience Australia’s Kongsberg EM3002D multibeam sonar
system. The EM3002D is a dual head system employing dynamically focused beams to gather high
resolution detail of the seafloor whilst maintaining a theoretical swath width up to 10 times the water
depth in coverage. In practice however, coverage of 4-6 times the water depth is more realistic to
achieve International Hydrographic Organization (IHO) Order 1a specifications using dual head
systems. The system operates the two sonar heads at different frequencies (293 and 307 kHz.). This
eliminates acoustic interference between the sonar heads. The multibeam product is comprised of two
overlapping swaths from the individual transducers mounted at approximately 40 degrees from the
horizontal.
During patch testing and equipment calibrations, it was noted that the starboard sonar transducer was
not performing optimally with considerable noise interference, the nature of which remained
unresolved during the survey. As a result the starboard head was partially decommissioned for the
remainder of the survey; see section A.6.1 of Appendix A.
3.2 Survey platform and survey operating parameters
The survey was conducted on the AAD workboat RV Howard Burton. The RV Howard Burton is an 8.5
m long science tender, equipped with twin 200hp 4 stroke outboard motors. A purpose built moonpool
allows the multibeam transducers to be raised and lowered, allowing access for maintenance, the
provision of incorporating a keel plate in order to operate the vessel at planing speeds for long transits,
and crucially, for the vessel to be recovered onto a trailer on a daily basis with minimal reconfiguration.
The setup of the vessel is shown in Figure 3.1 and Figure 3.2. During surveying the boat operational
speed was less than 7 knots, typically around 6-7 knots. GA Standard Operating Procedure for
Multibeam surveying recommends survey speed of 8-9 knots, and not less than 7 knots (Buchanan et
al., 2013) and these speeds are reasonable in average conditions and in charted areas. However, in
the hazardous waters off the Antarctic continent, some reduction in the recommended survey speeds
was necessary due to navigational hazards (sea-ice), and/or operations in uncharted areas.
3.3 Motion referencing unit and satellite positioning
The motion reference unit used was an Applanix POS MV 320 which supplied real-time motion data to
the Kongsberg Processing Unit (PU) and the proprietary Seafloor Information (SIS) acquisition
software and to all bathymetry data. The survey employed two independent Global Navigation Satellite
System (GNSS) based solutions for the Primary and Secondary positioning solutions. The Applanix
system used its default antennas to receive Marinestar G2 corrections which operated in parallel with
a high precision C-Nav 2050R Differential GPS system utilising a high-gain corrections antenna (see
Figure 3.1, Table 3.1).
8
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
The Applanix logs true heave data to its proprietary files, *.ATH, for subsequent re-application during
data post processing. The Applanix True Heave™ data (*.ATH file) significantly improves the heave
analysis and assists in reducing the effects of settling error and long period heave artefacts.
Figure 3.1 The RV Howard Burton approaching Casey Wharf for retrieval. Note the navigational GPS antennae
and the orange multibeam trolley. The sonar transducer heads are attached mechanically to the motion reference
unit (labelled) and the whole trolley lowered into the moonpool..The figure here shows the multibeam unit in a
partly lowered state. (Photo: D Forrest, IXSurvey).
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
9
Figure 3.2 The Multibeam trolley extended (left) and retracted (right). Note the Applanix motion reference unit at
the top of the multibeam mount and the hand winch for lowering and raising the transducer heads into position in
the moonpool. Data cables from the transducers and motion reference unit feed to the processing unit in the cabin
(out of view)
Table 3.1 GNSS systems used during survey
Positioning System
RTG Solution
Dates Used
Primary
Marinestar G2
30-DEC-2014 to 14-JAN-2015
Secondary
C-Nav
15-JAN-2015 to 30-JAN-2015
The POS MV and C-Nav equipment performed well throughout the survey with no faults or issues
experienced. The survey was referenced to the World Geodetic System 1984 (WGS84) zone 49
south. All data has been presented on the Universal Transverse Mercator (UTM) Projection.
3.4 Seafloor imagery and sampling
A Scielex™ drop camera system fitted with a co-linear mounted FIX NEO Light DX™ rated to 2000
lumen, with sufficient data cable for deployment to depth of 100 m was used during the survey
(Figure 3.3). A live feed monitor was positioned on the rear deck during camera deployments.
Although suitable for its intended use as a drop camera over a specific site, the camera was not
suitable for towed video transects necessary for benthic ecosystems assessments.
10
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
Figure 3.3 The drop camera provided by the Australian Antarctic Division. Drop camera in operation (left, photo
credit Glenn Johnstone, AAD). Camera-light package before deployment on rear deck of RV Howard Burton, note
the coiled orange data live feed cable and live feed monitor in black pelican case (right).
As a trial, a GO-PRO™Hero3 video camera in a waterproof casing (rated to 40 m) was attached to the
metal frame around the Valeport miniSVP instrument during several sound velocity profile
deployments to image the seafloor. This was successful to the 40 m depth limit of the GO-PRO™
casing and required no supplementary light source. This setup was also successfully deployed on the
shipek sediment sampler, up to depths of 40 m, and was so positioned as to image the seafloor at the
exact point of sample collection (Appendix Figure B.1).
Seafloor sampling (Figure 3.4) was undertaken using a mini shipek grab deployed by hand from the
instrument deck on the RV Howard Burton via a removable section of the starboard gunwales. The
locations of sample and video sites are tabulated in Appendix Table B.1 and shown in Figure 3.5.
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
11
Figure 3.4 Deployment of the ‘cocked’ shipek grab sampler by hand from the starboard side of the Howard
Burton. Note loading frame at lower centre.
12
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
Figure 3.5 Location of sediment sample and video stations conducted during survey GA-0348. Refer to
Appendix Table B.1 for further details.
3.5 Macroalgae spectral analysis
Spectral measurements of the dominant macroalgae species present in the shallow-water near-shore
Casey region were collected as a subsidiary dataset. This work was conducted with a field portable
ASD FieldSpec® Pro Handheld. These analyses complement unpublished spectral analyses of
bedrock and sediments conducted in 2010 by University of Tasmania researcher, Dr A. Lucieer.
These measurements will be used to develop a reference spectral library for potential satellite-based
bathymetry determinations and other satellite remote sensing studies. No further data analysis or
interpretation was conducted either during the survey or on return to Australia.
Macroalgae was dredged from the seafloor, from the wharf and coastal outcrops in the immediate
area. These samples were placed on a white background (inverted plastic flour drum lid) and analysed
according to the following conditions. The instrument was fitted with a 7.5 degree foreoptic, acquisition
parameters were 20 repeat sample readings for the Spectrum (S), 20 readings for Dark Current (DC)
and 40 readings of White Reference (WR, a specific calibrated tile, Figure 3.6) to calibrate and to
optimise noise to signal ratio during readings (Figure 3.7). The local conditions during acquisition were
nil cloud, nil wind, air temperature -3° C. Data files are available from GA in *.ASD format.
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
13
The analyses were conducted on three genus of macroalgae common in the photic zone in the Casey
region, Monostroma sp, Palmaria sp and Himantothalus sp (identification by J. Stark, AAD, pers
comm).
Figure 3.6 Field set-up of the ASD FieldSpec® Pro Handheld during acquisition of macroalgae spectra, Casey
wharf. The white tile being analysed is the White Reference (WR). The dive vessel, RV Pagadroma, is in the
background. Facing northwest (20/01/2015)
Figure 3.7 Field set-up of ASD FieldSpec® Pro Handheld during analysis of Monostroma sp. (20/01/2015)
14
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
3.6 Survey log
Out of the 40 days from the effective start of survey (22 Dec 2014) to demobilisation of the RV Howard
Burton (30 Jan 2015), 21.5 days of survey were possible, with a total of 14.5 days lost due to
compulsory station stand-downs. The daily log of the survey operations are shown in Table 3.2.
Table 3.2 Daily operations log for survey duration
Date
Location
27-29 OCT-2014
Brisbane (IXSurvey
offices)
10-14 NOV-2014
Kettering, TAS
5-DEC-2014
Board RSV Aurora
Australis (Voyage 2
Hobart to Casey)
5-12 DEC-2014
RSV Aurora Australis
12-DEC-2014
Arrive Casey
Remain on RSV Aurora Australis due to limited space on
station
13-21 DEC-2014
RSV Aurora Australis,
Casey
Station resupply and refuelling operations, all expedition
personnel engaged
18-DEC-2014
Casey
Arrival of Forrest at Casey station via A319 Airbus flight FA04a
19-DEC-2014
Casey
Survey team transferred to Casey
22-DEC-2014
Casey
Station stand-down post resupply operations, completed fitting
RV Howard Burton with multibeam equipment
23-DEC-2014
Casey
RV Howard Burton in water at Casey wharf for ‘bar check’ and
navigation valuation DGPS check
24-DEC-2014
Casey
Meeting with station operations manager, arrange field training.
Station shutdown at 12:00 for Christmas
25-26 DEC 2014
Casey
Station stand down for Christmas and Boxing Day
27-DEC-2014
Newcomb Bay
28-DEC-2014
Bailey Peninsula area
29-DEC-2014
Newcomb Bay
Trouble shooting faulty starboard sonar head
30-DEC-2014
Newcomb Bay
‘patch test’ completed, commenced MBES survey data
acquisition
31-DEC-2014
Powell Cove, Noonan
Cove, Orton Reef
01-JAN-2015
Casey
02-JAN-2015
Newcomb Bay
Survey data acquisition, faulty sonar head issue unresolved
and decommissioned for duration of survey
03-JAN-2015
Newcomb Bay
Sampling and benthic video data acquisition ½ day only (no
work permitted after 12 noon Saturday)
04-JAN-2015
Casey
Station stand down
05-JAN-2015
Casey
High winds (>40 knots), no survey
06-09 JAN-2015
Comments
Bench testing of multibeam hardware, operating software
upgrades
Sea-trials on RV Howard Burton and equipment testing
Survey team depart Hobart, from Selfs Point after bunkering.
Carson, Walker, Matthews, Cooksey and Lee on board
Transit to Casey station, Antarctica
‘Patch test’, UPS failure, replaced with a station unit for duration
of survey, noted interference on starboard side sonar head
Survey team field training
Survey data acquisition
Station stand down for New Year’s Day
Clarke Peninsula, Dahl Survey data acquisition
Reef region
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
15
Date
Location
10-JAN-2015
Newcomb Bay
11-JAN-2015
Casey
12-JAN-2015
16
Comments
Sampling and benthic video data acquisition ½ day only
Station stand down
Seaward of Shirley
Survey data acquisition
Island and O’Brien Bay
13-15 JAN-2015
Beall Reef region
Survey data acquisition
16-JAN-2015
Casey
High winds, no survey
17-JAN-2015
various
Sample acquisition ½ day only
18-JAN-2015
Casey
Station stand down
19-JAN-2015
Beall Reef region
20-JAN-2015
Casey
21-JAN-2015
Newcomb Bay
Survey data acquisition
22-JAN-2015
Casey
High winds, no survey
23-JAN-2015
Seaward of Clarke
Peninsula and Beall
Reefs area
24-JAN-2015
O’Brien Bay and Beall
Reef area
25-JAN-2015
Casey
Station stand down
26-JAN-2015
Casey
Station stand down (Australia Day)
27-JAN-2015
Robertson Channel,
Beall island area
28-JAN-2015
Newcomb Bay
29-JAN-2015
Casey
High winds, no survey
30-JAN-2015
Casey
Demobilise RV Howard Burton, consign freight for return to
Australia as per AAD deadline
31-JAN-2015
Casey
Forrest finalising bathymetry datasets and report
1-4 FEB-2015
Casey
Final packing and preparation for RTA
4-FEB-2015
Casey-Wilkins
Survey data acquisition
RV Howard Burton deployed to transport technicians to Frazier
Islands rookery, no survey. Conducted spectral analysis of
macroalgae, section 3.5
Attempt to mapping shoals (location uncertain on charts),
retreat due to poor sea conditions, revisit Beall Reef area
Sample acquisition ½ day only
Survey data acquisition, cut short by bad weather
Sample acquisition in PM after poor weather in AM
Return to Australia, flight A319 FA06B Wilkins to Hobart, end
survey
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
4 Preliminary interpretation of seafloor features
The bathymetric data collected during this survey, combined with that collected during the RAN-AAD
survey in 2013/14, reveal the seafloor morphology in unprecedented detail. Our preliminary
interpretation of the submarine geomorphology reveals several dominant features. The major features
(Figure 4.1) can be simplified into the following domains:

Crystalline bedrock or basement ‘highs’ (Section 4.1)

Fault and channel systems (Section 4.2)

Glacio-submarine features (Section 4.3)

‘Deep’ isolated basins (Section 4.4)
Figure 4.1 Figure showing the selected locations of seafloor geomorphology examples discussed in the text.
Inserts a-d are shown in greater detail in Figure 4.2.
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
17
Figure 4.2 Insets a-d enlarged from Figure 4.1. a) Detail of bedrock high in the Dahl Reef region; b) and c) Two
areas dominated by parallel submarine moraine sets, a prominent northwest trending fault scarp and a ‘U-shaped’
channel system, Newcomb Bay region. Gibney Reef on the extreme right centre of inset b); d) Isolated marine
basin to the north-west of Shirley Island. For geographic names see Figure 2.3. Bathymetry colour scale as
Figure 4.1.
4.1 Bedrock ‘highs’
Bedrock highs (Figure 4.2a) are characterised by complex, rugose and variable topography comprised
of crystalline metamorphic basement rocks, and are predominately steep sided knolls that can form
small shoals and reefs (e.g. Gibney and Dahl reefs, see Figure 4.3). This morphology is typical of the
areas seaward (west) of Clark Peninsula and Newcomb Bay and the east-west trending bathymetric
high of the Beall Reefs-Granholm Rock region near Beall Island (Figure 2.3). These regions are
flanked by deep north-west and west-northwest trending channels. Bedrock highs do not appear to be
overlain by significant sediment coverage. Onshore regions, such as exposed on Bailey Peninsula
(Figure 4.4) are thought to represent analogous exposed areas with geomorphological characteristics
as the marine ‘bedrock highs’.
4.2 Channels
One of the most striking seafloor features evident in the bathymetric data are the north-west trending
channels and linear features that most likely represent brittle bedrock fault systems (Figure 4.2b and c).
These features are present on the north shore of Newcomb Bay, O’Brien Bay, in the bedrock highs along
the Beall Reef region and Robertson Channel. These sub-parallel basement bedrock faults, ‘fractures’ or
joints have in places (e.g. north Newcomb Bay, Figure 4.2b and c) been preferentially eroded and
18
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
widened locally by glacial action to form narrow (200-400 m wide) U-shaped channels, with profiles
characteristic of glacially eroded valleys seen in the terrestrial environment. A secondary set of
southwest to west-southwest trending linear features are characterised by broad eroded channels.
These features are less distinct than the northwest trending set of channels and are sub-parallel to the
regional high-grade gneissic fabric exhibited by the basement rocks exposed onshore. The broad
features are evident, for example, between Beall Island and Beall Reefs, the seaward end of Clark
Peninsula. The general orientation of the coastline and channels in the Casey region suggest that these
linear features fundamentally control the regional coastal and seafloor geomorphology.
4.3 Glacial submarine landforms
Within the northwest trending channels, particularly within O’Brien Bay and northern Newcomb Bay,
distinct raised narrow and curved (convex seaward) seafloor features are a prominent feature
(Figure 4.2b and c). These seafloor features, presumably formed by glacial or glacio-fluvial processes,
resemble ‘moraines’ deposited at the terminus of channelized outlet glaciers that likely formed when
the ice sheet locally extended seaward beyond its present day limits. Limited seafloor images show
heterogeneous rocky detritus, consistent with diamictite which is typical of terrestrial moraines. The
channels in which these features occur in Newcomb (Figure 4.2b and c) and O’Brien Bays trend northwest initially then open out into broader west-northwest trending channels and deeper basins further
seaward. The ‘moraines’ are particularly well developed in northern Newcomb Bay, and may be up to
25 m higher than the surrounding seafloor. Many smaller ‘moraines’, about 5-10 m high, are also
easily discernible in the bathymetry.
Figure 4.3. Gibney Reef, exposed during low tide, facing south-west, Shirley Island in the distance (ca. 3 km).
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
19
Figure 4.4. Examples of bedrock geomorphology above the shoreline as an analogue for submarine ‘bedrock
highs’. Bailey Peninsula, facing south.
4.4 Basins
Sediment-filled ‘enclosed’ basins are present in O’Brien Bay, Newcomb Bay and northwest of Shirley
Island. These basins are enclosed, in that there is minimal or no outlet for bottom drainage (e.g.
northwest Shirley Island), or have limited drainage through a single channel (O’Brien and Newcomb
Bays). One good example of an enclosed basin (Figure 4.2d), approximately 1.5 km2 in area, is
located 1 km to the northwest of Shirley Island. It is roughly 130-135 m deep, with two ‘spillways’ or
sills to the west, roughly 200 m wide and 100 m deep, over which is the only bottom drainage to the
open ocean. This basin may represent a good location for coring accumulated sediments for postglacial geochronology investigations.
20
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
5 Concluding remarks
Bathymetric maps of the seafloor based on high-resolution multibeam sonar data are increasingly
recognised within the marine science, operations and environmental management communities as
important, fundamental datasets. Multibeam sonar data of the seafloor is analogous to, and as equally
useful as, topographic maps, aerial photographs and satellite data that underpins our understanding of
the terrestrial environment.
This high-resolution sonar survey, combined with the RAN-AAD survey in 2013/14, provides
visualisation of the seafloor in unprecedented detail, and permits development of evidence-based
marine environment management protocols, better understanding of the benthic environment for
ecosystem assessments, and improved navigational charts to reduce risk to maritime operations. It
also provides scientists with a valuable foundation for a diverse range of marine science and glacial
history investigations.
This report provides the technical and operational precis of the survey. The multibeam data and
supplementary datasets collected on this survey can be sourced at Geoscience Australia under
GeoCat number 83224, ‘Casey Station (Antarctica) Bathymetry Survey, GA-0348 / AAD 3326’. Copies
of the data may also be obtained at the Australian Antarctic Data Centre on the Australian Antarctic
Division web site. Unabridged contractor reports, containing detailed technical settings, calibrations
and GNSS checks are available on request from Geoscience Australia. Full interpretation of the
datasets incorporating bathymetry, backscatter (for substrate physical composition determinations)
and water column (possible macro-algae distribution) is being undertaken and will be published
elsewhere.
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
21
6 Acknowledgements
The successful implementation of this survey involved numerous people during the planning and
deployment stages. The authors wish to thank Jodie Smith, Alix Post, Scott Nichol (Geoscience
Australia), David Donohue, David Field (IXSurvey), Peter Waring (RAN) and Rhonda Bartley, Phillip
Tracey, Rick Van Enden and AAD technical and support staff at AAD head office (Kingston). In
particular, we wish to thanks the technical support from Ian Atkinson, Nick Dando and the team in the
Science and Support Laboratories section at Geoscience Australia.
We also thank the AAD expeditioners at Casey Station, particularly the plant operators, workshop
‘diesos’ and Doug McVeigh (Casey electronics engineer) during 2014/15 summer season, without
whose assistance the survey would not have been possible.
Hydrographic coxswains, LSHSO Hannah Lee and ASHSO Glen Cooksey (RAN), exhibited
professional and astute seamanship as coxswains for the duration of the survey.
The authors thank Floyd Howard and Justy Siwabessy (Geoscience Australia) for their professional
and constructive reviews.
This record is published with the permission of the CEO, Geoscience Australia. GEOCAT 87790.
22
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
References
Buchanan, C., Spinoccia, M., Picard, K., Wilson, O. and Sexton, M. J., 2013. Standard Operation
Procedures for a Multibeam Survey: Acquisition & Processing. Geoscience Australia Canberra.
2013/33, 34 pp.
O'Brien, P. E., Atkinson, I., Bowden, R., Forrest, D. & Paddison, J., 2010. Coastal Seabed Mapping
Survey, Vestfold Hills, Antarctica, February-March 2010 (AAS 2201) - Post Survey Report.
2010/47, 34 pp.
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
23
Vessel calibrations and operational
parameters
A number of calibrations and checks were conducted during the pre-survey vessel mobilisation in
Kettering, Tasmania (10-14 November 2014) including:

Motion Sensor Performance and Vessel Offset Calculations

MBES Patch Test (with repeat Patch Test conduction during the course of the Survey)

Vessel Draft Gross Error Check

Squat (dynamic draft) Trials

Bar check
A.1 Motion sensor performance and vessel offsets
The RV Howard Burton utilises an Applanix POS MV motion reference system. This unit was
calibrated by Nicole Bergersen of Acoustic Imaging during the pre-survey seatrials.
The RV Howard Burton has a valid navigation frame of reference installed and output at the target on the
Inertial Motion Unit (IMU) on the POS MV. Because the IMU is securely attached to the same moonpool
frame structure as the EM3002 sonar it can be assumed that the factory dimensional control (REF)
conducted on the IMU target to geometric centre between the two EM3002D sonar head centres (a
vertical distance of 1.405 m) is well-controlled and therefore can be added to the following lever arms:

REF to Primary GNSS (PGNSS)

REF to IMU

REF to Secondary GNSS (SGNSS)

REF to Centre of Rotation (CoR)
All serial output from the Applanix POS MV is at the geometric centre of the sonar heads. With the
validation of the position and orientation reference frame the latitude, longitude, roll, pitch, heading
and heave readings being parsed out to the sonar and sonar acquisition software are valid.
The lever-arm offset distances were checked manually by tape measure on site at Casey station, and
no reason was found to alter the initial values
A.1.1 Offset summary
Survey systems and software occasionally refer to different coordinate reference systems. In this
setup the following coordinate reference systems are used:

Applanix: X:+ve Fwd ,Y: +ve Starboard, Z:+ve Down

SIS: X:+ve Fwd ,Y: +ve Starboard, Z:+ve Down
24
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica

CARIS™: Y:+ve Fwd ,X: +ve Starboard, Z:+ve Down

Vessel: Y:+ve Fwd ,X: +ve Starboard, Z:+ve Up
To avoid confusion the offset values relative to the Vessel coordinate reference system are tabulated
below (Appendix Table A.1):
Appendix Table A.1 Vessel Coordinate System Offsets utilised during pre-survey sea trials and the main survey
Offset
X(m)
Y(m)
Z(m)
REF – Geometric centre (between sonar heads)
0.000
0.000
0.000
Defined
Primary GNSS (port Antenna)
-0.89
0.97
4.12
Phase centre
Secondary GNSS
0.91
0.99
4.13
Derived
Auxiliary GNSS
0.00
0.99
4.105
Phase centre
IMU
0.00
0.00
1.405
Phase centre
Waterline
-----
-----
0.750
Variable
0.000
1.100
1.100
Estimated
Vessel Centre of Rotation
Remarks
All offsets were entered in the respective configuration files within the POS MV and SIS software
packages to enable real time QC of corrected data during survey operations. The same vessel offsets
(with respective reference frame sign conventions) were used in CARIS™ HIPS for the postprocessing of all bathymetric data.
A.2 Multibeam echosounder (MBES) patch tests
Patch Tests were conducted on RV Howard Burton on 11 and 12 November 2014 to determine the
angular bias between the MBES transducers and the Motion Reference Unit (POS MV). An area of flat
seafloor in general depths of 20 m and containing a relatively steep slope were found, approximately
1.5nm NE of Kettering Marina, Tasmania, and were selected as the pre-survey patch test location
(Appendix Figure A.1).
Two further patch tests (on-site) were also conducted at Casey station immediately prior to
commencement (30/12/2014) of survey operations and near the completion of the survey (22/01/2015).
The first on-site Patch Test was also conducted on RV Howard Burton on 30 December 2014. An area
of flat seafloor in general depths of 60 m and an area containing a relatively steep slope were found,
approximately 1 km north of the boat ramp at Casey Station. These areas centred around 16°16.17’S
110°32.40’E were selected as the patch test location.
A second on-site Patch Test was conducted on RV Howard Burton on 22 January 2015 to confirm the
angular bias between the MBES transducers and the Motion Reference Unit (POS MV). A more
defined feature, in deeper water was used to test Pitch and Yaw, and a flatter site was chosen to
confirm Roll angles. The new sites were still in Newcomb Bay approximately 0.9-1.6 km north of the
boat ramp at Casey Station, centred around 66°16.00’S 110° 32.00’E.
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
25
Appendix Figure A.1 MBES Patch Test and pre-survey sea trials locations, Kettering, Tasmania. (Base figure
extracted from Australian Hydrographic Service chart AUS 173, D’Entrecasteau Channel, 1:75 000 Aug 2008).
A.2.1 Methodology
The procedure described in the CARIS™ Technical Note MBES Calibration 01.03.07 has been
observed for this project and is summarised below. The use of the dual head EM3002D MBES in
requires a slightly different patch test procedure from a single head system this is expanded as
follows:

Pitch Bias:
To resolve the pitch angular bias, two coincident lines run in opposite directions at
the same speed over a conspicuous object are compared in a similar manner in the HIPS
Calibration Tool. For best results, this test is conducted in deeper water to improve the angular
sensitivity of the derived values.

Yaw Bias:
The procedure to determine yaw bias is different for a single and dual head
transducer. For a dual system, the error may be different between the two heads – it is therefore
necessary to run calibration lines that will allow for the detection of the independent bias values.
Two lines must be run in different directions at opposite sides of a conspicuous feature, so that the
same feature is observed by the same beams of the transducer. This involves running different
lines for each transducer. Any apparent shift in the position of the object seen in the outer section
of the swath will indicate yaw bias.

Roll Bias:
Similar to the test for yaw, the test for roll bias requires treating the MBES
transducers separately. A set of reciprocal lines is run; one offset for the other so that the same
strip of seafloor is covered by the same transducer and a cross section (‘slice’) is compared across
the two lines. Any angular miss-match is attributable to roll bias.
26
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
A.2.2 Environmental conditions
Sea conditions were good for the duration of the Kettering pre-survey and on-site patch tests. SV dips
were conducted immediately prior to testing and subsequently applied during post-processing. True
Heave, through Applanix *.ATH files was also applied. The data was tide corrected using predicted
tide values for Hobart (Kettering pre-survey patch test) and Casey (for on-site patch test). The
recorded MBES data was relatively clean and requiring only minimal spike removal.
A.2.3 Results
A summary of the patch testing conducted are presented as follows:

Table of calibration values derived from the patch test;

MBES Calibration Forms (detailed reports available on request)
Appendix Table A.2 Multibeam Echosounder Patch test summary results
Roll Bias
Pitch Bias
Yaw Bias
Date
Port
Starboard
Port
Starboard
Port
Starboard
12-NOV-2014
0.18°
-0.16°
0.40°
0.40°
0.35°
-0.20°
30-DEC-2014
0.15
-0.15
-0.07
0.00
-0.60
-0.60
22-JAN-2015
-0.07
NA
-0.07
NA
0.20
NA
The second on-site Patch Test (22 Jan 2015) confirmed the veracity of values for Pitch and Roll
derived from earlier Patch Tests. In the case of Yaw, a 0.8 degree variance was found, it was
determined that the second test, which used a more prominent feature, and had the advantage of
better line planning and driving, gave the more robust result. Therefore, the values for the second test
were applied in post-processing to the entire data set by applying the later values to the original vessel
file. Unfortunately, a second patch could not be conducted on the STBD head due to failure of the
head. The initial values therefore remained relevant for the three and a half days in which that head
was operating.
A.2.4 CARIS™ offsets
The raw position used by SIS, was in effect the final position for the survey data. No further offset
values were entered into CARIS™. Patch Test calibration values were entered in CARIS™ HIPS
vessel file for the post-processing of raw survey data (.ALL). It should be noted that waterline offset
values entered into SIS are not carried through for bathymetric processing in HIPS, so in effect the
online values used in SIS do not influence the final processed bathymetry. To that end the waterline
offsets were entered into the CARIS™ HIPS vessel file (.HVF).The following calibration values were
the final values applied in CARIS™ HIPS.
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
27
Appendix Table A.3 Final calibration values utilised in CARIS™ processing
Roll Bias
Pitch Bias
Yaw Bias
Date applied
from
Port
Starboard
Port
Starboard
Port
Starboard
30-DEC-2014
0.15°
-0.15°
-0.07°
0.00°
0.20°
-0.60°
A.3 Vessel draft gross error check
As a check on the inputted offsets and vessel draft inputs a comparison was conducted between the
depths recorded to the Kongsberg *.all files and a physically measured depth at the time of recording.
A leadline was lowered to the seafloor while the vessel was alongside, and the survey system was
pinging. The resulting values were within 2 cm of one another.
A.4 Squat trial data
A.4.1 Methodology
The RV Howard Burton conducted operations to acquire Dynamic Draft or ‘Squat’ data on two
occasions. Squat is the phenomenon where a change in vessel speed leads to vertical displacement
of the vessel, which is a function of the hull design and speed through the water. These tests were
conducted on the 06 January and 22 January 2015. On each occasion the vessel was driven at
speeds ranging from 2 to 8 knots. The data from these runs was captured in POS MV files. No GNSS
post processing software was available on site. The lines were recorded with the aim that later post
processing of the GPS solution will generate data with enough resolution in the Z-axis to confirm the
limited squat behaviour observed on board.
Appendix Table A.4 Squat trial runs
Date (UTC)
Line
Average speed (kts)
0129_20150105_230309_HowardBurton_GA-0348
2.5
0129_20150105_230309_HowardBurton_GA-0348
4.6
0129_20150105_230309_HowardBurton_GA-0348
6.0
0129_20150105_230309_HowardBurton_GA-0348
8.2
0510_20150122_041343_HowardBurton_GA-0348
2.1
0510_20150122_041343_HowardBurton_GA-0348
4.0
0510_20150122_041343_HowardBurton_GA-0348
6.3
0511_20150122_042011_HowardBurton_GA-0348
7.9
05-JAN-2015
22-JAN-2015
A.4.2 Results
There was almost no evidence of squat observed on board the RV Howard Burton, and the data was
processed without the use of dynamic draft tables. It was determined that any movement in the Z-axis
due to squat was negligible and was discounted in the processing workflow. The data is however
available to determine squat values for application at a later date if required.
28
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
A.5 Bar check
As a confirmation of accurate bathymetric measurement, a Bar Check was conducted on 22 Dec 2014
alongside the wharf at Casey Station.
A.5.1 Methodology
The bar (a 3 m length of tube steel – wrapped in bubble wrap to improve detection) was suspended at
2 m below the water level, on calibrated/measured chain below the transducers. The beam angle of
the system was reduced to 20 degrees on each head and a gate placed on the return detection (0.5 –
2.3 m) data recorded while the bar height was monitored.
A.5.2 Preliminary results
Initially a discrepancy was found, as the data returned a consistently shallower depth than expected. It
was found that the chain had wrapped around the bar on one side, consequently raising the bar and
giving a reading that was shoaler than expected.
Once rectified, the system returned the expected 2.00 m below the water surface.
A.5.3 Processed results
The line data from the barcheck was processed through HIPS 8.1 in the same way that the survey
data is processed. (The exception in this case is that a zero tide function was used instead of real
world tides). This ensures that no gross errors are inherent in the processing stream. The resulting
data set was confirmed at 2.00 m.
On 20 January 2015 a second barcheck was undertaken. The following results confirm that data
acquisition and processing continued to compute accurate Z-values.
A.6 Equipment defects and issues
A.6.1 Kongsberg EM3002 starboard transducer
Following vessel trials during initial mobilisation phase at Kettering (TAS), all systems were functioning
well. It was noted however, that although the Kongsberg system passed all BIST tests, Head 548
(STBD) had a higher noise evaluation than Head 547 (PORT).
Upon mobilisation at Casey Station, all systems seemed to be functioning well and at the conclusion
of the bar check – every confidence was that the system was working as expected.
Upon proceeding to sea, it was apparent that when operating in waters deeper than 50 m, this higher
noise level was quite pronounced on the STBD sonar head. Beyond 60 m this resulted in evident
‘tearing’ of the data, and beyond 100 m all data outside the noisy part of the swath became unusable.
An image displaying this ‘tearing’ type effect is shown below (Appendix Figure A.2).
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
29
Appendix Figure A.2 Screen grab from Kongsberg SIS acquisition software illustrating the starboard sonar
transducer noise in 65m of water on 29/12/2014. The upper portion of the screen shows the ‘waterfall’ image, a
rendition of the sonar signal from both transducers as viewed from behind the vessel; in the water column looking
forward (the seafloor is the strong reflector running horizontally along the base of the image). Note the marked
‘ray’ of interference present in the starboard transducer. The bottom image is the imaged seafloor viewed from
above and behind, facing in the direction of vessel headway, showing the ‘tear’ in the imaged seafloor caused by
the interference.
Fault finding commenced initially with the rebooting of the entire Hydrographic Survey System (HSS).
This was soon followed by re-seating the Beam Forming and Signal Processing (BSP) cards and
cleaning the electrical contacts, still to no effect. The spare transducer cable was run to the STBD
head (548) however, the noise was still evident. Finally, the BSP boards were swapped around. The
noise remained pronounced and on the same head (STBD). Noise interference from the vessel was
ruled out through tests conducted whilst both the engines and the generator were shut down.
Discussions with Kongsberg representatives in Norway, Senior Surveyors at IXSurvey, and Ian
Atkinson (GA) concurred that the head itself (which has undergone refurbishment before), was at fault
and no repair would be possible in-situ.
The work-around that was developed involved simply reducing the swath during operations in waters
deeper than 50 m, and severely reducing the swath in waters greater than 100m deep. This resulted in
a swath with no greater than that of a single head mounted normally, but with the benefit of 320
beams in the same arc. This was at the expense of clarity on the water column, but as this was to be
the case in all future data acquisition, it was considered satisfactory.
On the morning of 7 January (local), the noise on the STBD sonar head was noticeably worse upon
system start-up. After some trials and investigations it was deemed counterproductive to continue
surveying in dual head mode in any but the shallowest of depths. An image displaying the increased
noise levels experienced is shown below (Appendix Figure A.3).
30
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
Appendix Figure A.3 Screen grab from Kongsberg SIS processing software illustrating the starboard sonar
transducer noise in 100m of water on 6/01/2015 (UTC)
Keeping in mind the intention to survey shoal and explore unsurveyed bays in the future, operations
continued using PORT head only but without reconfiguring the system to a single head mount. Lines
were subsequently run in order to achieve 200% coverage with only the PORT head, mounted at 40
degrees in the dual head configuration.
This configuration remained until demobilisation of the vessel. Only on very few occasions, working in
very shallow depths was the STBD head brought online again (and this only to guarantee no data
‘holidays’ in shoals where limited passes were possible).
The Starboard transducer has been returned to Kongsberg (Norway) for diagnosis and repair.
A.6.2 Uninterruptible power supply (UPS)
At the commencement of survey operations the system UPS failed. The Casey electronics workshop
examined the UPS, and it was found to be clogged with dust, and an electrical short circuit was
suspected during the start-up. The unit was irreparable on site. The delays caused by this malfunction
were prior to having permission to begin survey operations, and as a replacement UPS unit was
generously loaned to the project by the Casey electronics workshop, no survey time was lost.
A.6.3 240 volt petrol generators
The 240 volt power supply on the RV Howard Burton was provided by an AAD supplied petrol
powered generator (Honda 30kVA) in order to supply power to the multibeam and navigational
systems. The generator that was trialled in Kettering during the pre-mobilisation phase, failed during
survey. Failure occurred at the end of the survey day, after the transducers were brought inboard. A
replacement generator was loaned to the survey team from the Station mechanical workshops and
survey operations began the next day with no downtime.
The new vessel generator (a similar Honda 30kVA unit) was subsequently found to shut off during port
turns, probably due to a protective automated float switch cut-off. In these events the UPS unit did
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
31
take over powering the HSS but emitted no audible warnings and would subsequently shut-down at
the end of its battery life. After several occurrences the generator was remounted and the problem no
longer occurred.
A.6.4 SIS acquisition software
A frustrating problem with the HSS was the SIS acquisition system grid functionality. The grid failed
(‘locked up’) on several occasions and in some cases survey was suspended while the problem was
rectified, typically by a re-boot of the equipment.
A.7 Operational settings and parameters
A.7.1 Geodetic control
No new geodetic control was established for this project. The survey employed two independent
Global Navigation Satellite System (GNSS) based solutions for the Primary and Secondary positioning
solutions.
The survey was referenced (Appendix Table A.5) to the World Geodetic System 1984 (WGS84). All
data has been presented on the Universal Transverse Mercator Projection (UTM).
Appendix Table A.5 Geodesy parameter for the duration of survey
Parameter
Value
Horizontal Datum
WGS 84
Projection
Universal Transverse Mercator, Zone 49 South
Spheroid
WGS84
Latitude of Origin
00° 00'.000 S
Origin Longitude
110° 00'.000 E
False Easting
500 000.000mE
False Northing
10 000 000.000mN
A.7.2 Vessel draft and squat corrections
Vessel draft was measured regularly on board Howard Burton and applied online to the .ALL files via
SIS and during post processing trough CARIS™ HIPS.
It should be noted that while the waterline (draft measurement) can be, and is, entered into the SIS
acquisition system, this value only affects the online gridded data. Vessel draft must still be entered
into the CARIS™ processing software in order to achieve correct results.
A.7.2.1 Squat
No corrections for squat were applied in post processing within CARIS™ HIPS.
32
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
A.7.3 Backscatter
Backscatter data acquired by the Kongsberg EM3002D MBES is embedded in the Kongsberg .ALL
files. The .ALL file format contains the backscatter record when accessed via a suitable post
processing software package such as CARIS™ HIPS and SIPS, or QPS Fledermaus.
In order to facilitate the backscatter processing process, settings within SIS that affect the quality of
backscatter remained unchanged throughout the survey. The frequency of each head remained the
same; 293kHz and 307kHz. The pulse length used was always 150µs. The absorption coefficients
were calculated by the salinity method, and the salinity was assumed to be at 35ppt at all times. All
SVPs were processed through SIS at the time of acquisition in order to have the software create the
associated .ABS files. These files are located in the SVP folder of each day’s raw data.
In accordance with project specifications, no processing of recorded backscatter data has been
conducted as part of the survey. It is rendered in a raw state and will be processed in the future.
A.7.4 Tides & sounding datum
Observed tidal data from the Casey Station tide gauge was downloaded on a daily basis and used for
the reduction of soundings. The tidal model utilised in CARIS™ for the survey was a simple single
station model.
A.7.4.1 Casey tidal station
The following information is supplied by AAD Technical Support on the Casey Tidal Station.
A 250 mm diameter stainless steel tube is enclosed in the wharf (Appendix Figure A.4,
Appendix Figure A.5); the bottom of this tube communicates with the ocean via a 1 m long horizontal
leg. The whole of the inside of this tube is lined with a double walled ABS, foam filled insulator.
Two high precision pressure gauges are positioned at known heights, 2 meters apart within this tube.
Also in this tube are two heat traces and four thermistors. Power and data cables run from the tube
back to the wharf Site Hut some 20 m distant.
In the Site Hut, signals from the pressure sensors and thermistors are processed, logged and
transmitted via a network connection.
The wharf gauges are accessible for downloading via the network. Both gauges stream 30 second
and 3 minute average data.’
Details of the Casey tide gauge equipment are tabulated in Appendix Table A.6.
Appendix Table A.6 Casey Tide gauge information
Area
Detail
Owner / Operator
Australian Antarctic Division
Gauge Type.
2x Paroscientific Digiquartz pressure sensors
Data interval
10-minute
Gauge Time Zone
UTC
Remarks
Continuous data
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
33
The following map extract and photographs show the general location of the site.
Appendix Figure A.4 Tide gauge location at Casey wharf, pink circle upper right of figure, (base map - AAD map
catalogue number 14294 ‘Casey Station Limits’)
Appendix Figure A.5 Casey Tide Gauge at northwest corner of wharf (photo courtesy of D Forrest)
34
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
A.7.4.2 Sounding datum
Sounding Datum details are shown in Appendix Figure A.6. No levelling or further checks were
conducted on the gauge as part of the survey.
The tidal levels and datum specified for sounding reductions are shown below:

Mean Sea Level (MSL) is 0.22 m above Zero Reference Level (RL in Appendix Figure A.6).

Lowest Astronomical Tide (LAT) is 0.74 m below ZRL

MSL is 0.96 m above LAT
Top of Rod (TG RM)
1.7261m
MSL (this analysis) = MSL (2015)
0.22m
RL = 0.0m
0.96m
0.74m
LAT (2015)
Appendix Figure A.6 Sounding Datum relationships
Note:

Tide gauge reference mark (Top of Rod) is 1.7261 m above zero reference level. The upper
sensor is 0.5492 m below RL = 0.0m and the lower sensor is 2.5557 m below RL = 0.0 m. Refer to
Casey_Wharf_dimension.txt for details.

Tidal prediction datum for Casey (ID #20120) is LAT, which is 0.96 m below MSL (2015) and
should be used for sounding reductions.

Tidal datum’s for 2014 adopts 0.98 m below MSL as the prediction datum, and the change was
instigated for 2015 to remove the long term mean sea level variation. As less than 4 hours of
survey data was gathered prior to 1 Jan 2015, the 2015 datum has been used to reduce all data.
A.7.4.3 Application of tidal data and survey datum
All initial MBES data processing was conducted using LAT as the sounding datum. On completion of
the project, the data was re-tided to the MSL datum (the GA reference datum for bathymetric surveys),
remerged in HIPs and new base surfaces created.
MSL is the final datum for all products. All ASCII data is referenced to the MSL datum.
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
35
A.7.4.4 Possible approaches to improve tidal accuracy
The accuracy of the single station model in use obviously decreases with distance from the tide station
(Casey Wharf). Although it is undoubtedly possible to improve the accuracy of the tidal model through
increasing the number of tidal stations, work involved with such options would be significant and not
necessarily worth the effort considering that even with the current tidal regime all processed MBES
data is within specifications.
The exception to this might possibly be the use of GNSS heights in combination with a refined geoidal
model which would reduce or even remove the reliance on terrestrial base tidal observations and
effectively remove the requirement for a tidal model and associated sources of error. To this end the
‘Process – Compute GPS Tide’ function was run in CARIS™ HIPS in order to facilitate this type of tidal
analysis in future post processing.
36
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
Sample, video/camera and sound
velocity profile locations
B.1.1 Sampling
B.1.1.1 Sample and video nomenclature
All samples are labelled according to the Geoscience Australia standard naming format for marine
samples as follows: survey ID, station number, sample type code, sample number, subsample (if any).
Sample types for this survey is either GR (= SHIP grab sampler) or CAM (video camera imagery). No other
sample types were collected (for further details on the sampling, the reader is referred to section 3.4).
For example at station 3 (Appendix Table B.1), a seafloor grab sample and video footage was taken at
that single site. The full sample identification for the grab sample at this site is GA0348/03/GR02. This
translates to, at station 3, a SHIPEX grab was taken and was the second SHIPEX sample taken
during the survey. No subsamples were taken.
Similarly, at station 03, the video imagery identification is GA-0348/03/CAM03, indicating that at this
site, the video was the third camera footage sequence taken on the survey.
The column ‘sampleno’ is the GA generated sample number for the sediment samples following return
GA to facilitate archiving and internal laboratory processing.
In a number of sites (e.g. station 4) a grab sample was attempted, but no sample was retrieved due to
a predominately rocky bottom, an example of which can see seen in Appendix Figure B.1.
Appendix Figure B.1 Image taken on a SHIPEX grab sampler with a GO-PRO™ showing the seafloor, preventing
collection of material at many sites due to the course-grained rocky armour. Site GA-0348/36/CAM14, UTC 28Jan-2015.
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
37
Appendix Table B.1 Samples and video locations for survey GA-0348
Station
Sample_Type
Sample_ID*
sampleno
Latitude
Longitude
Depth
(m)
Comments
1
CAM
01/CAM01
-
-66.258
110.463
30.0
nil sample
2
GRAB / CAM
02/GR01,
02/CAM02
2231530
-66.253
110.535
3.4
medium sand
3
GRAB / CAM
03/GR02,
03/CAM03
2231532
-66.255
110.526
25.0
sandy silt, anoxic
4
GRAB
nil return
-
-66.262
110.540
18.0
nil sample
5
GRAB / CAM
05/GR03,
05/CAM04
2231534
-66.261
110.553
7.0
sandy with cobbles
6
CAM
06/CAM05
-
-66.253
110.501
17.4
GO-PRO™ footage
7
CAM
07/CAM06
-
-66.254
110.520
34.4
GO-PRO™ footage
8
GRAB / CAM
08/GR04,
08/CAM07
2231536
-66.262
110.529
62.0
brown muddy fine
sand
9
GRAB / CAM
09/GR05,
09/CAM08
2231538
-66.269
110.538
64.5
green silty mud,
broken molluscs
10
GRAB / CAM
10/GR06,
10/CAM09
2231540
-66.246
110.461
58.2
poor yield, some
cobbles
11
GRAB
nil return
-
-66.245
110.520
46.0
nil sample
12
GRAB
12/GR08
2231542
-66.266
110.513
40.0
gravel, pebbles,
coarse sand
13
GRAB
13/GR09
2231544
-66.270
110.466
62.8
poor yield, fine sand
14
GRAB
nil return
-
-66.294
110.513
34.4
nil sample
15
GRAB
nil return
-
-66.295
110.512
63.2
nil sample
16
GRAB
nil return
-
-66.286
110.492
28.2
nil sample
17
GRAB
nil return
-
-66.291
110.479
94.1
nil sample
18
GRAB
nil return
-
-66.290
110.442
48.2
nil sample
19
GRAB
19/GR15
2231546
-66.295
110.502
65.0
green fine sandy
mud
20
GRAB
nil return
-
-66.297
110.510
72.0
nil sample
21
GRAB
21/GR17
2231548
-66.308
110.463
40.0
fine sandy mud
22
GRAB
22/GR18
2231550
-66.296
110.444
53.0
angular pebbles
23
GRAB
23/GR19
2231552
-66.298
110.452
98.0
sandy mud
24
GRAB
nil return
-
-66.295
110.453
48.0
nil sample
25
GRAB
nil return
-
-66.301
110.471
20.0
nil sample
26
GRAB
26/GR22
2231554
-66.303
110.474
13.0
greenish fine sandy
mud
27
GRAB
nil return
-
-66.275
110.520
10.0
nil return
28
GRAB
28/GR24
2231556
-66.276
110.516
17.0
angular pebbles
29
GRAB
29/GR25
2231558
-66.277
110.521
30.0
fine sandy silt
30
GRAB
nil return
-
-66.293
110.377
50.5
nil return
31
GRAB
nil return
-
-66.293
110.379
53.3
nil return
38
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
Station
Sample_Type
Sample_ID*
sampleno
Latitude
Longitude
Depth
(m)
Comments
32
GRAB / CAM
32/CAM10
-
-66.293
110.377
39.8
nil return
33
GRAB / CAM
33/CAM11
-
-66.305
110.453
31.9
nil return
34
GRAB / CAM
34/CAM12
-
-66.305
110.454
39.6
nil return
35
GRAB / CAM
35/GR31,
35/CAM13
2231560
-66.272
110.562
39.0
green mud
36
GRAB / CAM
36/CAM14
-
-66.277
110.525
27.0
nil sample, GOPRO™ footage
37
GRAB / CAM
37/CAM15
-
-66.273
110.550
36.8
nil sample, GOPRO™ footage
38
GRAB / CAM
38/GR34
2231562
-66.276
110.551
37.0
green muddy silt
39
GRAB / CAM
39/GR35
2231564
-66.271
110.561
40.0
green silty mud
40
GRAB
40/GR36
2231566
-66.266
110.544
82.1
green silty mud with
molluscs
41
GRAB
41/GR37
2231568
-66.265
110.506
70.0
medium sand
42
GRAB
nil return
-
-66.262
110.518
74.0
nil return
B.1.2 Sound velocity sensor and profile locations
Fifty one sound velocity profile casts through the water column were measured using an Applied
Microsystems Valeport miniSVP sound velocity profiler. The unit was battery powered and deployed
and retrieved from the rear of the RV Howard Burton manually via rope. The locations and date and
time (UTC) of the ‘dips’ are listed in Appendix Table B.2)
B.1.2.1 Sound velocity characteristics
Sound velocity (SV) proved more variable than expected. Early sounding operations were conducted
in the small shallow bays on the northern shore of Newcomb Bay. Strong variation between the hull
Sound Velocity Sensor (SVS) and the surface sound speed of the initial profiles prompted several dips
in those areas. Observation of considerable ‘melt water’ entering the bay in torrents corresponded to
very slow sound speed velocities in the first meter or two of the water column. The result was that the
SV of the water column that in some areas required many more sound velocity dips to maintain survey
accuracy requirements. In total, 49 SV dips were conducted during MBES operations. Constant
vigilance with regard to spatial and temporal variation in SV profiles resulted in good correlation of
data. Where there was excessive freshwater discharge concentrated in small bays, pockets of highly
variable SV were created. In these areas some artefacts where noticed in the processed seafloor
surfaces. Judicious use of the refraction editor on three lines in a previously unsurveyed bay in the
vicinity of Orton reef has removed the greater part of this artefact. The lines in question were 0054,
0055 and 0056. The result was that all data is within the accuracy requirements for the survey.
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
39
Appendix Table B.2 Locations of sound velocity profile casts.
40
UTC date
UTC time
Latitude
Longitude
27-Dec-2014
01:56
-66.268
110.537
30-Dec-2014
03:11
-66.267
110.537
30-Dec-2014
04:32
-66.262
110.549
30-Dec-2014
05:18
-66.262
110.551
30-Dec-2014
22:07
-66.262
110.550
30-Dec-2014
23:44
-66.261
110.552
30-Dec-2014
23:51
-66.262
110.550
30-Dec-2014
23:58
-66.264
110.549
31-Dec-2014
00:07
-66.264
110.535
31-Dec-2014
02:13
-66.254
110.525
31-Dec-2014
03:40
-66.254
110.474
01-JAN-2015
21:56
-66.259
110.502
01-JAN-2015
22:50
-66.256
110.476
01-JAN-2015
23:46
-66.265
110.491
02-JAN-2015
04:34
-66.265
110.467
02-JAN-2015
05:30
-66.278
110.483
05-JAN-2015
23:30
-66.254
110.512
06-JAN-2015
05:25
-66.251
110.488
06-JAN-2015
21:29
-66.270
110.508
07-JAN-2015
05:04
-66.235
110.445
07-JAN-2015
21:56
-66.244
110.480
07-JAN-2015
23:41
-66.249
110.511
08-JAN-2015
05:14
-66.254
110.520
08-JAN-2015
21:19
-66.250
110.512
09-JAN-2015
00:50
-66.233
110.518
09-JAN-2015
03:23
-66.297
110.447
09-JAN-2015
04:00
-66.265
110.457
11-JAN-2015
22:11
-66.256
110.474
12-JAN-2015
2:54
-66.271
110.442
12-JAN-2015
03:09
-66.278
110.475
12-JAN-2015
05:02
-66.278
110.414
12-JAN-2015
22:13
-66.276
110.476
12-JAN-2015
22:51
-66.278
110.413
13-JAN-2015
03:51
-66.284
110.412
13-JAN-2015
04:16
-66.285
110.476
13-JAN-2015
21:27
-66.279
110.450
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
UTC date
UTC time
Latitude
Longitude
13-JAN-2015
22:01
-66.286
110.410
14-JAN-2015
04:58
-66.298
110.363
14-JAN-2015
21:55
-66.286
110.474
14-JAN-2015
23:07
-66.290
110.363
15-JAN-2015
01:09
-66.295
110.433
19-JAN-2015
05:34
-66.287
110.471
20-JAN-2015
21:06
-66.275
110.529
20-JAN-2015
23:19
-66.273
110.550
21-JAN-2015
02:34
-66.271
110.556
22-JAN-2015
06:02
-66.275
110.529
22-JAN-2015
21:58
-66.232
110.367
23-JAN-2015
01:34
-66.299
110.466
26-JAN-2015
21:34
-66.290
110.393
26-JAN-2015
23:07
-66.283
110.469
27-JAN-2015
00:41
-66.270
110.561
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
41
Acronyms used in report
Appendix Table C.1 Acronyms or abbreviations utilised in the report
Acronym used in text
AAD
Australian Antarctic Division
AHO
Australian Hydrographic Office
ASPA
Antarctic Specially Protected Area
ASV
Antarctic Survey Vessel (e.g. ASV Wyatt Earp)
ATH
Applanix True Heave
BIST
Built In Self-Test (Kongsberg™ systems check)
BM
Bench Mark
BSP
Beam Forming and Signal Processing
CD
Chart Datum
CoG
Centre of Gravity
COTS
Commercial off the Shelf
CRP
Common Reference Point
CSAR
CARIS™ Spatial Archive file format
DGST
Deployable Geospatial Support Team
GA
Geoscience Australia
GIS
Geographic Information System
GNSS
Global Navigation Satellite System
HIPS
Hydrographic Information Processing System (CARIS™)
HSS
Hydrographic Survey System
IHO
International Hydrographic Organisation
IMU
Inertial Motion Unit
INS
Inertial Navigation System
IXSurvey
IXSurvey Australia Pty Ltd (contracted to GA for duration of survey)
LAT
Lowest Astronomical Tide
MBES
Multi Beam Echo Sounder
MRU
Motion Reference Unit
MSL
Mean Sea Level
PDOP
POS MV
42
Full Context
Position Dilution of Precision
Applanix™ Position Orientation System – Marine Vessel
QPS
Quality Positioning Services™ (Fledermaus software)
RAN
Royal Australian Navy
REF
≡ Factory Dimensional Control
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
Acronym used in text
RL
ROS
RP
Full Context
Reference Line
Report of Survey
Reference Point (See CRP)
RSV
Research and Supply Vessel (e.g. RSV Aurora Australis)
RTG
Real Time GIPSY (a proprietary real-time GPS correction methodology)
RV
SAR
SBES
SD
SIPS
SIS
Research Vessel (e.g. RV Howard Burton)
Search and Rescue
Single Beam Echo Sounder
Sounding Datum
Sonar Imaging Processing System (CARIS™)
Seafloor Information System (Kongsberg™ acquisition software)
STBD
Starboard
STW
Set to Work
SV
Sound Velocity
SVP
Sound Velocity Profile
TPU
Total Propagated Uncertainty
UTC
Universal Time Coordinated
UPS
Uninterruptible Power Supply
WCD
Water Column Data
WGS
World Geodetic System 1984
ZRL
Zero Reference Line
Seafloor Mapping Survey, Windmill Islands and Casey region, Antarctica
43