Metadata Report for BODC Series Reference Number 1903785

• 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

Bathymetry

The single-beam (MBANZZ01) contains significantly more noise than the multi-beam channel. However, much of the periods with absent value recordings appear to mirror those observed in the multibeam channel. Flags were assigned to the absent values, unrealistic noisy data and where records in the channel moves away from the baseline bathymetry. The high level of noise and the abundance of absent values exceed 50% and therefore the channel was not retained.

RRS James Cook JC165 Navigation Quality Control Report

Position

Position channels look good. Two gaps just at the start and end of the dataset, which can be trimmed off at the end of processing. flags were automatically applied to this.

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 bathymetry channels show similar patterns with the single-beam and the multi-beam following GEBCOâ??s trend. The quality of the multi-beam dataset is moderate containing some noise and periods with only absent value readings. Flags have been assigned to the absent values and to the unrealistic noisy values.

The single-beam contains significantly more noise than the multi-beam channel. However, much of the periods with absent value recording appear to mirror those observed in the multibeam channel. The high level of noise and the abundance of absent values appears to exceed 50% of the data.

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 EM122 12kHz Multibeam Echosounder

The EM122 is designed to perform seabed mapping to full ocean depth with a high resolution, coverage and accuracy. Beam focusing is applied both during reception and transmission. The system has up to 288 beams/432 soundings per swath with pointing angles, which are automatically adjusted according to achievable coverage or operator defined limits.

This model uses both Continuous Wave and Frequency Modulated sweep pulses with pulse compression on reception, in order to increase the maximum useful swath width. The transmit fan is split in several individual sectors, with independent active steering, in order to compensate for the vessel movements.

In multiplying mode, two swaths per ping cycle are generated, with up to 864 soundings. The beam spacing is equidistant or equiangular and the transmit fan is duplicated and transmitted with a small difference in along track tilt, which takes into account depth coverage and vessel speed, to give a constant sounding separation along track. In high density mode, more than one sounding per beam can be produced, such that horizontal resolution is increased and is almost constant over the whole swath.

The EM122 transducers are modular linear arrays in a Mills cross configuration with separate units for transmit and receive. If used to deliver sub-bottom profiling capabilities with a very narrow beamwidth, this system is known as SBP120 Sub-Bottom Profiler.

The specification sheet can be accessed here Kongsberg EM122.

Specifications

EM122 versions

RRS James Cook JC165 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 James Cook JC165 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-POSMV_GPS.gps

yyyymmdd-000000-gyro-POSMV_GYRO.gyr

yyyymmdd-000000-sb_depth-EM122_DEPTH.depth

yyyymmdd-000000-EA600-EA640_DEPTH.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. Both the EA640 single-beam echo-sounder and EM122 multibeam echo-sounder follow GEBCOâ??s trend. Unrealistic noisy values and absent data were flagged using BODC in-house EDSERPLO software. The EM122 multibeam echo-sounder data is a quality source of bathymetry.

Calibration

No field calibrations have been applied.

Project Information

Marine LTSS: CLASS (Climate Linked Atlantic Sector Science)

Introduction

CLASS is a five year (2018 to 2023) programme, funded by the Natural Environment Research Council (NERC) and extended until March 2024.

Scientific Rationale

The ocean plays a vital role in sustaining life on planet Earth, providing us with both living resources and climate regulation. The trajectory of anthropogenically driven climate change will be substantially controlled by the ocean due to its absorption of excess heat and carbon from the atmosphere, with consequent impacts on ocean resources that remain poorly understood. In an era of rapid planetary change, expanding global population and intense resource exploitation, it is vital that there are internationally coordinated ocean observing and prediction systems so policy makers can make sound evidence-based decisions about how to manage our interaction with the ocean. CLASS will underpin the UK contribution to these systems, documenting and understanding change in the marine environment, evaluating the impact of climate change and effectiveness of conservation measures and predicting the future evolution of marine environments. Over the five-year period CLASS will enhance the cost-effectiveness of observing systems by migrating them towards cutting edge autonomous technologies and developing new sensors. Finally, CLASS will create effective engagement activities ensuring academic partners have transparent access to NERC marine science capability through graduate training partnerships and access to shipborne, lab based and autonomous facilities, and modelling capabilities.

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: