Metadata Report for BODC Series Reference Number 1964964

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

Problem Reports

No Problem Report Found in the Database

RRS Discovery DY090 Navigation Quality Control Report

Position

Position channels look good. There was a gap just at the start of the dataset but this got trimmed off at the end of processing. Flags were automatically applied to this also.

Heading

Heading channel looks good. There are some large fluctuations within the permitted maximum and minimum parameter values and there are some parts of the datasets where absent values have been recorded. These absent values were automatically flagged.

Bathymetry

The Multibeam channel contains no data and therefore does not compare to GEBCO.

The Single Beam channel looks very good overall with only approximately 15% of the data flagged. It contains some noisy patches and some drop-outs but still compares well with GEBCO. The noisy patches and drop outs were flagged accordingly. There are also some absent values recorded at the beginning and the end of the single beam channel which will be trimmed off.

Data Access Policy

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

Narrative Documents

RRS Discovery Cruise DY090 Underway Document

Cruise Details

Kongsberg EA640 Single Beam Echosounder

The EA640 single beam echosounder comprises a standard EA600 (fitted with a standard transducer) and an additional, non-standard 10 kHz transducer.

The standard EA600 is a single beam echosounder with full ocean depth capability designed for bathymetric surveys. It measures water depth by monitoring the travel time of an acoustic signal that is transmitted from the ship, reflected off the seabed and received back at the ship.

The main components of the system are hull-mounted transducers linked to general purpose transceivers (GPTs). Up to four GPTs, each controlling one or more transducers, may be operated simultaneously. The GPT generates a signal, which is transmitted into the water column as an acoustic pulse by the transducer array, and the returning echo is recorded by the GPT. GPTs are in turn linked to a combined display and processor, where adjustments (such as sound-speed corrections) may be applied to the data. Available frequencies span from 12 to 710 kHz, and each GPT may operate at a separate frequency. A variety of transducers is available for water depths up to 11,000 m.

The EA600 stores all data internally but has a USB port which allows the possibility of connecting a CD-ROM/DVD drive to read and write the data. All echo data can be stored as files: bitmap, sample, depth or sidescan data.

In deeper waters, the EA600 supports a multipulse function, allowing for a higher pinger rate. While on passive mode, the pinger is normally attached to a device, with the purpose of tracking and displaying its current depth.

Specifications for a standard EA600 echosounder

Further details can be found in the manufacturer's specification sheet for the standard EA600 system.

RRS Discovery DY090 Navigation Instrumentation

Instrumentation

Trimble Applanix Position and Orientation Systems for Marine Vessels (POSMV)

The Position and Orientation Systems for Marine Vessels (POSMV) is a real time kinematic (RTK) and differential global positioning system (DGPS) receiver for marine navigation. It includes an inertial system that provides platform attitude information. The instrument provides accurate location, heading, velocity, attitude, heave, acceleration and angular rate measurements.

There are three models of Applanix POSMV, the POS MV 320, POS MV Elite and the POS MV WaveMaster. POS MV 320 and POS MV WaveMaster are designed for use with multibeam sonar systems, enabling adherence to IHO (International Hydrographic Survey) standards on sonar swath widths of greater than ± 75 degrees under all dynamic conditions. The POS MV Elite offers true heading accuracy without the need for dual GPS installation and has the highest degree of accuracy in motion measurement for marine applications.

Specifications

POS MV 320

POS MV WaveMaster

POS MV Elite

¹ One Sigma, depending on quality of differential corrections
² Whichever is greater, for periods of 20 seconds or less

Further details can be found in the manufacturer's specification sheet.

RRS Discovery DY090 Navigation Data Processing Procedures

Originator's Data Processing

The data were logged by the TECHSAS (TECHnical and Scientific sensors Acquisition System) system into daily NetCDF files. The TECHSAS system is used as the main data logging system on NMF-SS operated reserach vessels. The daily TECHSAS NetCDF navigation and bathymetry files provided to BODC were used for BODC processing. Data were additionally logged into the RVS Level-C format files which have been archived at BODC.

Files delivered to BODC

BODC Data Processing

Data were banked at BODC following standard banking procedures. Data were averaged to 60 second intervals.

The originator's variables were mapped to appropriate BODC parameter codes as follows:

yyyymmdd-000000-position-Applanix_GPS_DY1.gps

yyyymmdd-000000-gyro-GYRO1_DY1.gyr

yyyymmdd-000000-EA600-EA640_DY1.EA600

All the reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag.

Position

A check was run on positional data to identify gaps and improbable values (through the calculation of speed). There were drop outs in the positional data at the start and end of the file. These were flagged and trimmed after processing was complete.

Ship Velocities

Ship velocities were calculated from the main latitude and longitude channels using standard BODC procedures.

GEBCO

GEBCO bathymetry was added to the file using the main latitude and longitude channels.

Distance Run

Distance run was calculated from the main latitude and longitude channels, starting from the beginning of the file, using BODC standard procedures.

Bathymetry

Bathymetry data were screened independently as well as against GEBCO bathymetry measurements. The EA640 single-beam echo-sounder compares well and follows GEBCO's trend. There is no Multibeam data and therefore nothing to compare to GEBCO. Unrealistic noisy values and absent data were flagged using BODC in-house EDSERPLO software. The EA640 single-beam dataset is a quality source of bathymetry.

Calibration

No field calibrations have been applied.

Project Information

Controls over Ocean Mesopelagic Interior Carbon Storage: COMICS

COMICS is a four-year collaborative research project that aims to quantify the flow of carbon in the ocean?s ?twilight? zone in order to accurately model global climate change. This ?twilight? zone is the part of the ocean between 100m and 1000m below the sea surface, where only a small amount of light from the sun can still penetrate.

By investigating carbon dynamics in the ocean interior, COMICS will help to improve predictions of future global climate change.

The COMICS project is led by the National Oceanography Centre and is a collaboration between the British Antarctic Survey and the universities of Queen Mary London, Liverpool, Oxford and Southampton. The project received funding from the Natural Environmental Research Council and runs between April 2017 and 2021.

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

No Fixed Station Information held for the Series

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: