Title

NESP Biodiversity Hub Hunter Marine Park Towed Video Imagery

Data Quality Statement

Name: Data Quality Statement

Protocol: WWW:DOWNLOAD-1.0-http--download

Description:

Data quality statement for NESP Biodiversity Hub Hunter Marine Park Towed Video Imagery

Function: download

Code

c16ffe39-fb1d-4ace-8a6f-efa73a4939a6

Name

ISO 19115

Edition

2016

Code identifying the spatial reference system

4283

Topic category

Title

ANZLIC Search Words

Reference date

2008-05-16

NSW Place Name

Port Stephens Great Lakes Worimi

Coordinate reference system

Authority code

urn:ogc:def:cs:EPSG::

Code identifying the coordinate reference system

5711

End position

N/A

Contact info

Contact position

Data Broker

Organisation name

NSW Department of Climate Change, Energy, the Environment and Water

Telephone number

131555

Email address

data.broker@environment.nsw.gov.au

Web address

https://www.nsw.gov.au/departments-and-agencies/dcceew

Responsible party role

pointOfContact

Lineage

Video surveying was undertaken following the recommendations detailed in 'Field Manuals for Marine Sampling to Monitor Australian Waters' ( https://www.nespmarine.edu.au/field-manuals-marine-sampling-monitor-australian-waters). Details of the NSW DPIE towed video system and equipment are provided in 'SeaBed NSW: Standard Operating Procedures of multibeam surveying' (https://www.environment.nsw.gov.au/-/media/OEH/Corporate-Site/Documents/Research/Our-science-and-research/seabed-nsw-standard-operating-procedures-multibeam-surveying-190101.pdf). XYZ positional accuracy of the still imagery is better than XY (3 degrees of slant range [eg. 2.6m radius @ 100m]; <1m POS MV GPS G2 and POS to USBL offset) and Z (~0.2m based on USBL and tow-fish camera P-sensor with 0.54m offset). Imagery was obtained during the period 21 October 2019 – 31 October 2020 using a DSLR still camera (Towed Digital Stills - TDS) and forward looking live-feed (fibre) video (Towed Digital Video - TDV). TDS were captured at 2s intervals along 80-90 x 200m transects and characteristically ~1m from the seabed with dual green lasers (spaced 100mm) for measuring seabed distance (horizontal). TDS were re-labelled using NSW DPIE naming convention (NSWDPIE_TDS_NESP_Hunter_Location_Site_transectnumber_Dateyyyymmdd_TimeUTChhmmss). Image (JPG) time-stamping in UTC extracted from associated EXIF (Exchangeable Image File Format) metadata; Transect metadata file (CSV) for each transect contains the following columns: 1) Filename (as above); 2) Timestamp yyyy-mm-dd hh:mm:ss in UTC; 3) Latitude_TDS (Y GPS coordinate of TDS from USBL); 4) Longitude_TDS (X GPS coordinate of TDS from USBL); 5) Depth_TDS (Z stills camera depth in metres = derived from Pressure-sensor on TDV + physical offset TDS to TDV Pressure-sensor (0.54m); 6) Latitude_Ship (vessel Y coordinate); 6) Longitude_Ship (vessel X coordinate); 7) Sounder_Ship (raw vessel depth sounder output in metres); 8) COG_Ship (vessel heading in degrees); 9) SOG_Ship (vessel speed over ground in knots); 10-12) Roll_SHIP, Pitch_SHIP, Yaw_SHIP of Ship; 13) Depth_USBL (Z offset calculated from USBL transponder to transceiver using slant range); 14) Bearing_USBL (direction from vessel to USBL in degrees); 15) Flag (Numerical data flag of range 1 – 3 indicating source of positional data, method outlined in ‘Absolute External Positional Accuracy’, NaN = True fish position). Image and image metadata records (generated in csv format) were uploaded to NSW SEED Amazon Web Service for access and annotation in Squidle+.

Limitations on public access

Effective date

2020-07-16

Explanation

Water column imagery has been edited out of the dataset provided here but available upon request.

Effective date

2020-07-16

Explanation

Where drop-outs of GPS positioning of the tow fish occurred, an interpolated value was calculated as described in the Lineage statement above. Forward looking video and recorded tow-fish parameters (i.e. roll/pitch/heave) are also available but not provided with this digital still dataset.

Effective date

2020-05-18

Explanation

As the imagery is acquired using a moving platform some images may or may not capture part of the same section of seabed in subsequent images. Survey speed of ~1kt (0.51m/s); image capture rate 1 image every 2 seconds; and approximate area of seabed captured in each image (0.5 - 2m2); 2 laser pointers denote a horizontal distance of 10cm where visible. nb: tow-fish roll, pitch and heave values are recorded by the video camera and saved within the video data file.

Effective date

2020-05-18

Explanation

XY position of fish is determined by relative position of USBL transponder (fish) to transceiver (vessel). GPS position is G2 quality (<0.4-0.5m XYZ in realtime equiv. RTK) and is relative to the vessels Centre of Mass (reference frame 0:0:0) with a 2.4m forward offset (X = -1.5) from transceiver to COM entered in the USBL software (Y = 0). USBL heading offset is checked following each installation (nominally 23 degrees from centreline) and USBL (Tracklink, USA) precision is 3 degrees of slant range value. Original still image time-stamping is synched with computer UTC (<1s) but image naming convention utilises USBL/Video text feed based on POS MV time ss:mm:hh dd:mm:yyyy (UTC) output. The Tracklink USBL system suffers from drop outs (noise, power) for fish positioning and so when dropouts occurred the following protocol was followed when processing and interpolating positioning data: 1. Extract raw USBL data and partition into transects: interpolate (running average) where gaps are <10s: marked as FLAG 1 in the metadata file; 2. Extract GPS and Fish position (and other data) aligned with timestamps for each image (image to USBL time offset <1s); 3. Import ship and fish positions into Arc, then identify outlier points using 4m radius filter for successive UBSL fish position fixes; delete values and interpolate (running average) where gap is <10s; mark as FLAG 1 in metadata file. 4. Determine a median and SD of layback for true fish fixes and generate new fish position values over periods of 10s and as calculation of the new fish position relies on the last fish position there is likely to be an increase in positional error for the assumed fish-position over time. To rectify this, we applied an incremental (linear) offset/adjustment to ensure that the end of the ‘drop-out’ period aligned with next available USBL fish position in the sequence (i.e. when USBL positioning returned); marked as FLAG 3.

Effective date

2020-07-16

Explanation

No non-quantitative attributes are provided here

Contact position

Data Broker

Organisation name

NSW Department of Climate Change, Energy, the Environment and Water

Telephone number

131555

Email address

data.broker@environment.nsw.gov.au

Web address

https://www.nsw.gov.au/departments-and-agencies/dcceew

Responsible party role

pointOfContact

Contact position

Data Broker

Organisation name

NSW Department of Climate Change, Energy, the Environment and Water

Telephone number

131555

Email address

data.broker@environment.nsw.gov.au

Web address

https://www.nsw.gov.au/departments-and-agencies/dcceew

Responsible party role

pointOfContact