Metadata Report for BODC Series Reference Number 1902179

• 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

BAS Long Term Monitoring and Survey Program James Clark Ross Cruise JR20071029 (JR184) Underway Navigation Data Quality Report

Bathymetry

N flags were applied to absent values. M flags applied throughout the cruise period when dropouts or reflection from the surface was identified in 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 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.

Kongsberg Seatex Seapath 200 GPS and Gyrocompass

The Seapath 200 is a highly accurate, real-time heading, attitude and position information system that integrates the best signal characteristics of Inertial Measurement Units (IMU) and Global Positioning System (GPS), using a differential GPS method to acquire this data.

The high-rate motion data is obtained from the Seatex MRU5 inertial sensor and two fixed baseline GPS carrier-phase receivers. The raw data is integrated in a Kalman filter in the Seapath Processing Unit. The IMU contains an accurate linear accelerometer and Bosch Coriolis force angular rate gyros (CFG).

This system is equipped to utilise up to six different DGPS reference stations, it checks for consistency within measurements from the different sensors to ensure reliability and rejects noisy data or reports its inaccuracy. The data is available through various output protocols, RS-232, RS-422 and Ethernet.

This instrument is no longer in production; the main characteristics are presented below, and the specification sheet can be accessed here Kongsberg Seatex Seapath 200 .

Specifications

Sperry Marine MK-37 Gyrocompass

A family of instruments that contain a controlled gyroscope which seeks and aligns itself with the meridian and points to true north. They use the properties of the gyroscope in combination with the rotation of the earth and the effect of gravity. The effects of varying speed and latitude are compensated for by the use of manually operated controls. Models MOD I, MOD O, MOD D, MOD D/E are all with an analog output Step or/and Syncro. MOD VT is the latest model with NMEA Data output as well.

Further specifications for MOD VT can be found in the manufacturer's specification document.

Further information for MOD D/E can be found in the user manual.

BAS Long Term Monitoring and Survey Cruise RRS James Clark Ross JR20071029 (JR184) Underway Navigation Instrumentation Document

Navigation data were obtained through different instruments, but as the Seatex provides the position information for the multibeam system, it is considered by the originator, as a primary source of data so, unlike the other positioning streams, this stream was processed. Unprocessed data from the different navigation streams is available upon request.

The following table presents the instruments that collected data during the cruise:

BAS Long Term Monitoring and Survey Cruise RRS James Clark Ross JR20071029 (JR184) Underway Navigation Processing Procedures Document

Originator's Data Processing

Four files with processed data and one file with raw data were received at BODC. Data collection started on 29 October 2007 and ended on 20 November 2007.

The originator's procedures implemented throughout the cruise consisted of data retrieval from the previous 24h and logging those into subdirectories on the ship's intranet system.

Navigation instruments were located on the ship's monkey island, above the bridge.

Data processing was carried out at BAS on selected data streams. The ship has four positioning systems, but as the Seatex GPS provides the input latitude and longitude for the multibeam positioning, it is considered as a primary source of data, so processing was carried out on this stream but not on the others.

The processing procedures carried out by the originator include:

• check for duplicate dates and times
• standardising time
• check for gaps in data
• check data against defined thresholds
• interpolation and flagging
• unit conversion

Files delivered to BODC

* Note that although the filename is EM120, the instrument is actually a EM122.

BODC Data Processing

Parameter codes defined in BODC's parameter dictionary were assigned to originator's variables. No unit conversion was applied as the originator's units are equivalent to the units defined on the BODC vocabulary. Data were loaded into BODC's database using established data banking procedures.

jr184_seatex_exactsec

jr184_gyro_exactsec

ea600

Position

Processing and screening procedures including checks on positional channels. No speed fails or gaps were found in the data. Once ALATGP01 and ALONGP01 were considered good, screening was performed on the remainder navigation channels.

Distance run

Distance travelled data were rederived from the position channels. M flags applied during channel creation and reflect the cycles flagged in the originator's position data.

Ship's velocities

Northward and eastward velocities were derived from ALATGP01 and ALONGP01. During screening procedures, M flags were applied to anomalous data and N flags to null cycles.

Ship's orientation

HEADCM01 was screened and M flags applied to cycles were sudden changes in ship's orientation were considered anomalous.

Bathymetry

Both bathymetry channels were screened and N flags applied to absent data. M flags were applied to all instances where dropouts or reflection were identified in the data. The two channels were compared and the single beam echosounder channel (MBANZZ01) has more data and less flags overall and therefore the multibeam channel was not included in the final file.

Project Information

No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Western Core Box

The British Antarctic Survey undertakes cruises to determine krill biomass as part of the ongoing assessment of the status of the marine ecosystem in the region of South Georgia. This unique time series, known as the Western Core Box, which has taken place since 1996 is funded by Natural Environment Research Council (NERC) British Antarctic Survey Long Term Monitoring programme.

The survey area is located in an on and off shelf survery area (figure.1), which comprises of an acoustic grid survey of 8 transects each of 80 km in length. Standard data collection includes underway biological echosounder acoustic transaects, CTD profiles, stratified and targetted RMT8 hauls of macrozooplankton and micronekton and a set of moorings which provide temporal coverage and a year round set of observations.

The specific aims of the WCB are:

• To quantify the interannual variability and long-term change in the mesoscale distribution and abundance of Antarctic krill.
• To quantify the the interannual variability and long-term change in the mesoscale distribution and abundance of other plankton/micronekton.
• To examine interannual varaibility in the context of environmental variability (climate variability).
• To examine prey availiability in the context of predator and fishery demand.

Figure 1. Western Core Box Survey Area (BAS, 2017).

A list of Western Core Box cruises are shown below.

References

British Antarctic Survey (2017). POETS-WCB. Available at: https://www.bas.ac.uk/project/poets-wcb/ [Accessed 2017].

Related Fixed Station activities are detailed in Appendix 1

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:

Appendix 1: Western Core Box

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.