Seafloor Mapping Survey, Windmill Islands and Casey region ... · Record 2016/03 | GeoCat 87790....

Record 2016/03 | GeoCat 87790

Seafloor Mapping Survey, Windmill Islands and Casey region, AntarcticaGA-0348 Post Survey Report, December 2014 - February 2015

Carson, C. J., Forrest, D., Walker, G., the Deployable Geospatial Support Team, Post, A., Smith, J., Bartley, R. and Tracey, P.

APPLYING GEOSCIENCE TO AUSTRALIA’S MOST IMPORTANT CHALLENGES www.ga.gov.au

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. Geoscience Australia 2. IXSurvey Australia 3. Royal Australian Navy 4. 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 provided under a Creative Commons Attribution 4.0 International Licence. (http://creativecommons.org/licenses/by/4.0/legalcode)

Geoscience Australia has tried to make the information in this product as accurate as possible. However, it does not guarantee that the information is totally accurate or complete. Therefore, you should not solely rely on this information when making a commercial decision.

Geoscience Australia is committed to providing web accessible content wherever possible. If you are having difficulties with accessing this document please email [email protected].

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

http://creativecommons.org/licenses/by/4.0/legalcode

mailto:[email protected]

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 Appendix AA.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 Appendix BB.1.1 Sampling ..................................................................................................................................37 B.1.2 Sound velocity sensor and profile locations .............................................................................39

Acronyms used in report .....................................................................................................42 Appendix C

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 near-shore 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


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.


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) Location Comments

1 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


Priority area Area (km2) Location Comments

7 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 km2 of area (Figure 2.2) ranging from the intertidal zone (roughly 1 m) to 161 m of water depth, adding to the 7.0 km2 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 RAN-AAD coverage from 2013/14 season. Bathymetry contours and priority areas as shown in Figure 2.1 are not shown for clarity.


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.


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).


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).


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.


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.


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.


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.


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)


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 Comments

27-29 OCT-2014 Brisbane (IXSurvey offices)

Bench testing of multibeam hardware, operating software upgrades

10-14 NOV-2014 Kettering, TAS Sea-trials on RV Howard Burton and equipment testing

5-DEC-2014 Board RSV Aurora Australis (Voyage 2

Hobart to Casey)

Survey team depart Hobart, from Selfs Point after bunkering. Carson, Walker, Matthews, Cooksey and Lee on board

5-12 DEC-2014 RSV Aurora Australis Transit to Casey station, Antarctica

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 ‘Patch test’, UPS failure, replaced with a station unit for duration of survey, noted interference on starboard side sonar head

28-DEC-2014 Bailey Peninsula area Survey team field training

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

Survey data acquisition

01-JAN-2015 Casey Station stand down for New Year’s Day

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 Clarke Peninsula, Dahl Reef region



Date Location Comments

10-JAN-2015 Newcomb Bay Sampling and benthic video data acquisition ½ day only


12-JAN-2015 Seaward of Shirley 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


19-JAN-2015 Beall Reef region Survey data acquisition

20-JAN-2015 Casey RV Howard Burton deployed to transport technicians to Frazier Islands rookery, no survey. Conducted spectral analysis of macroalgae, section 3.5

21-JAN-2015 Newcomb Bay Survey data acquisition


23-JAN-2015 Seaward of Clarke Peninsula and Beall

Reefs area

Attempt to mapping shoals (location uncertain on charts), retreat due to poor sea conditions, revisit Beall Reef area

24-JAN-2015 O’Brien Bay and Beall Reef area

Sample acquisition ½ day only


26-JAN-2015 Casey Station stand down (Australia Day)

27-JAN-2015 Robertson Channel, Beall island area

Survey data acquisition, cut short by bad weather

28-JAN-2015 Newcomb Bay Sample acquisition in PM after poor weather in AM


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 Return to Australia, flight A319 FA06B Wilkins to Hobart, end survey


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.


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


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 north-west 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).


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 post-glacial geochronology investigations.


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.


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.


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.


Vessel calibrations and operational Appendix Aparameters

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


• 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) Remarks

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

Vessel Centre of Rotation 0.000 1.100 1.100 Estimated

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 post-processing 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.


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.


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

Date Roll Bias Pitch Bias Yaw Bias

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.


Appendix Table A.3 Final calibration values utilised in CARIS™ processing

Date applied from

Roll Bias Pitch Bias Yaw Bias

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)

05-JAN-2015

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

22-JAN-2015

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

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.


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).


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).


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


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.


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


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)


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)

LAT (2015)

RL = 0.0m

MSL (this analysis) = MSL (2015)

0.22m

1.7261m

0.74m

0.96m

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.


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.


Sample, video/camera and sound Appendix Bvelocity 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 28-Jan-2015.


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


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






19 GRAB 19/GR15 2231546 -66.295 110.502 65.0 green fine sandy mud


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



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




Station Sample_Type Sample_ID* sampleno Latitude Longitude Depth (m) Comments

32 GRAB / CAM 32/CAM10 - -66.293 110.377 39.8 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, GO-PRO™ footage

37 GRAB / CAM 37/CAM15 - -66.273 110.550 36.8 nil sample, GO-PRO™ 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


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.


Appendix Table B.2 Locations of sound velocity profile casts.

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


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


Acronyms used in report Appendix C

Appendix Table C.1 Acronyms or abbreviations utilised in the report

Acronym used in text Full Context

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 Position Dilution of Precision

POS MV Applanix™ Position Orientation System – Marine Vessel

QPS Quality Positioning Services™ (Fledermaus software)

RAN Royal Australian Navy

REF ≡ Factory Dimensional Control


http://en.wikipedia.org/wiki/Australian_Antarctic_Division

Acronym used in text Full Context

RL Reference Line

ROS Report of Survey

RP 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 Research Vessel (e.g. RV Howard Burton)

SAR Search and Rescue

SBES Single Beam Echo Sounder

SD Sounding Datum

SIPS Sonar Imaging Processing System (CARIS™)

SIS 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 ... · Record 2016/03 | GeoCat 87790....

Documents

Transcript of Seafloor Mapping Survey, Windmill Islands and Casey region ... · Record 2016/03 | GeoCat 87790....