Metadata Report for BODC Series Reference Number 1816198

• 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 James Cook JC088 navigation quality control report

Quality control report

Bathymetry

As part of the Matlab processing, the originator has removed spikes. Depth errors appeared during 06:00:00 GMT and 07:26:24 GMT on 19/07/2013. The incorrect depths were blanked (NaN) and filled with the respective gebco depths.

Navigation

No data quality issues concerning navigation were found. (BODC assessment)

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

Kongsberg EA600 Single Beam Echosounder

The 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.

The EA600 replaced the EA500 in 2000.

Specifications

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

RRS James Cook JC088 navigation instrumentation

Instrumentation

The following scientific navigational and bathymetric systems were fitted.

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 James Cook JC088 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 research vessels. Data were additionally logged into the RVS Level-C format files.

Each Level-C file was read into Matlab so that further processing, calibration and quality control could be performed on selected variables.

GPS data were logged from up to three GPS sources: POSMV 3.8, Seapath 200 and AshTech ADU5. Ship's gyrocompass readings and echosounder depth were also logged. Data from all instruments were logged to the RVS Level-C system. Standard navigation processing steps were then carried out using the relmov, bestnav and prodep programs.

Any headings in either POSMV or Heading > 360 or <0 were removed. Subsequent comparison of the headings recorded by the ships gyro and the POSMV GPS revealed a median offset of -0.52 degrees (gyro > POSMV).

Corrected depths were obtained from the processing routine prodep. The programme corrects the raw depths recorded by the hull mounted, single beam echo sounder (Simrad EA600) for local variations in sound velocity using values from the Carter tables published by the Hydrographic Office. These tables divide the world's oceans into areas of similar water masses and provide depth corrections for each area. The program uses a navigation file to find the position of each depth record and applies the relevant correction.

The Matlab navigation and bathymetry files provided to BODC were used for BODC processing. Data were additionally logged into the RVS Level-C format files and TECHSAS which have been archived at BODC.

For more detailed information on the Originator's underway data processing, please see the cruise report

Files delivered to BODC

BODC Data Processing

Underway data files were merged into a single file using time as the primary linking key. Data were banked using BODC standard banking procedures. Data resolution were reduced to 60 second intervals.

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

JC88_NAV1_1s.mat

JC88_NAV2_1s.mat

Screening

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 gaps in the positional data and which were linearly interpolated to remove them during BODC processing.

Ship Velocities

Ship velocities were calculated from the main latitude and longitude channels using standard BODC procedures creating channels - APEWGP01 and APNSGP01.

Distance Run

Distance run was calculated from the main latitude and longitude channels, starting from the beginning of the file, using BODC standard procedures creating channel - DSRNCV01.

Bathymetry

The EA600 echo-sounder has been corrected for local sound velocities. Bathymetry data were screened independently as well as against GEBCO bathymetry measurements.

Calibration

No field calibrations have been applied to the data at BODC.

Project Information

Fluxes Across Sloping Topography of the North East Atlantic (FASTNEt)

Background

The FASTNEt consortium was funded to deliver NERC's Ocean Shelf Edge Exchange Programme. Commencing in October 2011, this four year study aims to couple established observational techniques, such as moorings and CTDs, with the very latest in autonomous sampling initiatives - including use of Autosub Long Range and gliders. With the aid of novel model techniques, these observations will be utilised to construct a new paradigm of Ocean/Shelf exchange.

Shelf edge regions mark the gateway between the world's deep oceans and shallower coastal seas, linking terrestrial, atmospheric and oceanic carbon pools and influencing biogeochemical fluxes. Shelf edge processes can influence near-shore productivity (and fisheries) and ultimately affect global climate.

FASTNEt brings together researchers from multiple UK organisations. Further collaboration has been established with five Project Partners: the UK Met Office, Marine Scotland Science, Agri-Food and Biosciences Institute, Marine Institute Ireland and Scripps Institution of Oceanography.

Scientific Objectives

• To determine the seasonality of physical gradients and exchange across the shelf edge by deploying new observational technologies (gliders, Autosub Long Range) and established techniques (long term moorings, drifters)
• To quantify key exchange mechanisms and to collect new data targeted at testing and improving high resolution models of the shelf edge, by carrying out detailed process studies in contrasting regions of the shelf edge of the NE Atlantic margin
• To develop a new parameterisation of shelf edge exchange processes suitable for regional-scale models, using improved resolution numerical, and new empirical models constrained by the observations
• To test the new parameterisations in a regional model in the context of making an assessment of inter-annual variability of ocean-shelf exchange.

Fieldwork

Three survey sites on the UK shelf edge have been selected for FASTNEt. These are a) the Celtic Sea shelf edge, b) Malin shelf and c) North Scotland shelf. Fieldwork is centred around two research cruises. The first, to the Celtic Sea, on RRS Discovery in June 2012. The second cruise visits the Malin shelf on RRS James Cook, during summer 2013. In addition to these dedicated cruises, opportunist cruise activity to the North Scotland shelf has been agreed with project partner Marine Scotland Science. Autonomous technologies will complement observations made during the cruises and provide knowledge of seasonal and inter-annual variability in exchange processes.

Instrumentation

Types of instruments/measurements:

• Gliders
• Autosub Long Range
• Drifter buoys
• Scanfish
• Microstructure profilers
• Moored CTD/CT loggers and ADCPs
• Shipboard measurements: CTD, underway, nutrients (and other discrete sampling), LADCP, ADCP.

Contacts

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: