Metadata Report for BODC Series Reference Number 1762328

• 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 Clark Ross Cruise AMT24 (JR20140922) Navigation and Bathymetry Data Quality Document

Navigation channels

Care should be taken regarding the positional information from 26/10/2014 01:22:00 to 26/10/2014 10:28:00. This is because the navigation sensors did not provide any data during this period with no reliable information available in the bridge log either. Data from an external source were inserted and flagged in order to provide additional complementary information to the Seapath 320+.

Data Access Policy

Open Data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

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 320+ Precise Heading, Attitude and Positioning Sensor

The Seapath 320+ is a navigational system that combines two Global Navigation Satellite System (GNSS) receivers with a MRU 5+ inertial sensor to provide high resolution and accuracy positional data. The inertial sensor employs linear accelerometers and unique microelectromechanical systems (MEMS)-type angular rate gyros to provide 0.01 RMS pitch and roll accuracy. The GNSS receivers can use multiple satellite constellations (GPS, GLONASS and Galileo, when available), and combine data from these to improve heading and positional measurements. In case of missing data from one GNSS receiver, the other receiver provides position and velocity, and the inertial sensor provides heading from its internal rate sensors.

The main characteristics are presented below, and the specification sheet can be accessed here Kongsberg Seatex Seapath 320+ .

Specifications

RRS James Clark Ross Cruise AMT24 (JR20140922) Navigation and Bathymetry Instrument Description Document

Instrumentation

The following instruments were used to generate the navigation and bathymetry dataset.

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.

RRS James Clark Ross Cruise AMT24 (JR20140922) Navigation and Bathymetry Processing Document

Originator's Data Processing

The navigation and bathymetric data were measured by several different instruments and the data were logged every second to the SCS system. Each instrument logged data to one individual in comma separated ACO format file and the header information was stored in corresponding TPL files. The transferred latitude and longitude navigation data originated from the Seatex Seapath 320+ GPS, as this was the best quality positional dataset out of the original files. The best quality bathymetry data were obtained from the EM122 Kongsberg Maritime multi-beam echo-sounder. The ship's orientation comes from the Sperry Marine Mk 37 gyrocompass. The ship's speed and direction over ground was calculated from the positional data during processing of the data.

The table below shows the original files delivered to BODC that contained the data in the final data series, along with start and end dates and times of each file.

BODC Data Processing

The ACO files provided by the originator were archived at BODC and transferred into internal BODC format using established BODC data banking procedures. The originators files contained many parameters that were not transferred because they were not relevant to the final data set; some were related with the instruments behaviour or acquisition checks. Several channels were re-derived by BODC.

The table below provides a description of the originators channels transferred, along with the BODC parameter codes and units assigned. Unit conversions were applied when data were supplied in knots and nautical miles. BODC processing procedures then included reduction through averaging, checking navigation channels for improbable values, working out speed over ground, and screening the data for anomalous values. All files were averaged to 60 second intervals.

Derived channels

Distance run was derived using the seatex latitude and longitude channels using the BODC Matlab function 'disrun'.

Ship's north and east velocity channels were derived using the seatex latitude and longitude channels, using the BODC Matlab function 'velcal'.

Sample Calibration

No sample calibrations were applied to these data.

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

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: