Metadata Report for BODC Series Reference Number 1809811

• 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 D376 navigation quality control report

Quality control report

Bathymetry

As part of the Matlab processing, the originator has removed spikes.

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 Simrad EA500 bathymetric echosounder

The EA500 is a bathymetric echosounder that can be used in water as deep as 10,000 m. It features triple frequency operation with a separate digitiser for each channel and high transmitted power with an instantaneous dynamic range of 160 dB. The instrument can operate with several pulses in the water simultaneously and has bottom tracking capabilities. A wide range of transducers (single beam, split beam or side-looking) is available and the ping rate is adjustable up to 10 pings per second. The split beam operation measures the athwartships inclination angle of the seabed.

This instrument was introduced in June 1989 and and replaced by the EA 600 in 2000.

Specifications

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

Fugro SeaSTAR 9200-G2 Receiver

The SeaSTAR 9200-G2 is a dual frequency (L1/L2) receiver that incorporates global positioning system (GPS) and global navigation satellite system (GLONASS) reception capability while tracking the Fugro L-Band satellite broadcast of Differential Global Satellite Navigation System (DGSNS) corrections. These corrections can also be received via internet, as a backup.

The SeaSTAR 9200-G2 can be used in conjunction with other services as HP (GPS network solution), XP (GPS or orbit and clock solution) and G2 (Composite GPS/GLONASS orbit and clock solution). These are also dual frequency carrier phase solutions, which allows for a decimeter level accuracy.

The 72 channels received by the SeaSTAR include GPS- L1 C/A code and L1/L2/L2C full cycle carrier, GLONASS- L1/L2 full cycle carrier, Satellite Based Augmentation System (SBAS) and the Fugro L-Band service.

Specifications

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

RRS Discovery D376 navigation instrumentation

Instrumentation

The following scientific navigational and bathymetric systems were fitted.

Please note that no information on the type of Gyrocompass used on cruise D376 was supplied to BODC and therefore BODC have assumed that the instrumentation was the same as used on D379.

RRS Discovery D376 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 the Trimble 4000 differential GPS, the Ashtech GPS and Seastar 9200. 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 AshHeading or Heading > 360 or <0 were removed. Heading readings from the gyrocompass between 23/06/2012 18:37:09 and 24/06/2012 00:10:33 were noisey and were also removed. Subsequent comparison of the headings recorded by the ships gyro and the AshTech GPS revealed a median offset of -0.622 degrees (gyro > AshTech).

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 EA500) 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:

D376_NAV1_1sec.mat

D376_NAV2_1sec.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 these gaps were present due to a crash in the TECHSAS system. During BODC processing, these gaps were linearly interpolated to remove them.

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 EA500 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: