Metadata Report for BODC Series Reference Number 1918944

• 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

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.

Ashtech GG24 receiver

The GG24 is an all-in-view Global Positioning System (GPS) and Global Navigation Satellite System (GLONASS) receiver that blends GPS and GLONASS into a single position solution. This receiver uses all available satellites from both systems to obtain the best position information.

The three-dimensional position and velocity are calculated when tracking any combination of five satellites. Up to five independent measurements are determined every second, with no interpolation or extrapolation from previous solutions.

Specifications

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

Ashtech Global Positioning System receivers (ADU series)

The ADU series of Global Positioning System (GPS) receivers are designed to give real-time three-dimensional position and attitude measurements. Attitude determination is based on differential carrier phase measurements between four antennas connected to a receiver, providing heading, pitch and roll, along with three-dimensional position and velocity.

The ADU2 model receives information from 48 channels, while the upgraded model (ADU5) uses 56 channels. The ADU5 also features a unique Kalman filter with user selectable dynamic modes to match operating conditions. It also incorporates signals from Satellite Based Augmentation Systems (SBAS) and features an embedded 2-channel 300 kHz beacon receiver for easy differential GPS (DGPS) operations.

Specifications

Further details can be found in the manufacturer's specification sheets for the ADU2 andADU5.

Furuno GPS/WAAS Navigator GP32

The GP32 is an advanced GPS navigator with a Wide Area Augmentation System (WAAS) receiver which can receive up to 12 discrete GPS channels, all-in-view, and also has DGPS capabilities.

The WAAS applies correction data by means of geostationary satellites. The reference stations on earth monitor the GPS constellation and route GPS error data to the WAAS satellite via the master earth station.

This equipment is comprised of a compact unit designed for coastal activities with several display modes, e.g. Plotter, Nav Data, Steering, Highway, Speedometer and two other costumisable modes. The data can be viewed in WGS-84 or other geodetic systems.

Specifications

The equipment's specification sheet can be accessed Furuno GP32

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 and Monitoring Survey James Clark Ross Cruise JR20101221 (JR245, JR246, JR247) Underway Navigation Instrumentation Document

The instruments used to collect these dataset are presented in the table below. The Seatex is the primary source of positioning, therefore is the only positioning data stream included in the final file. The Chernikeef Mk5 Aquaprobe for ships speed and Kongsberg EM122 multibeam echosounder have not be included in the final file and are therefore not listed below. All instruments were located on the ship's monkey island, above the bridge.

BAS Long Term and Monitoring Survey James Clark Ross Cruise JR20101221 (JR245, JR246, JR247) Underway Navigation Processing Procedures Document

Originator's Data Processing

Data processing was completed by the originator in Unix and Matlab using modified versions of programs developed by Mike Meredith (BAS) and then read over into netCDF format. Procedures included data loading and visual checks for the positioning streams. The originator sent one file with processed data, including: ship's position, north and eastward velocities, course and speed made good, travelled distance and heading. This file covers a period from 20 December 2010 00:00 hours to 15 December 2011 00:00.

Bathymetry and ship's heading had to be retrieved from files processed at the BAS Polar Data Centre (BAS-PDC) as it was either not processed by the originator or the data sent by the originator could not be converted to a format compatible with BODC's specifications.

The procedures applied by the originator include:

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

Files delivered to BODC

BODC Data Processing

The files mentioned above were selected for data banking as they contain the best version of processed position and unprocessed heading and bathymetry. Data were banked at BODC following standard data banking procedures, including reduction through averaging, checking navigation channels for improbable values, working out speed over ground, and screening the data for anomalous values.

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

The file also contained smg, cmg,heading_av, pitch and roll however these parameters were not transferred as they were derived by the originator or could be extracted from a more accurate source.

Screening

All the reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag, missing data by both setting the data to an appropriate value and setting the quality control flag.

Position (ALATGP01 and ALONGP01)

A check was run on the position data and several gaps were identified. All gaps were interpolated and an appropriate flagged applied to all affected cycles. The data interpolated for the gap identified from 30 December 2010 14:06:00 hours to 30 December 2010 14:59:0 hours should be used with caution.

Ship's velocities (APEWGP01 and APNSGP01)

Ship's eastward and northward velocities were calculated from the main latitude and longitude channels. No gaps were identified and for those cycles where the position data were interpolated, the ship's velocities channels were assigned an M flag.

Distance Run (DSRNCV01)

Distance run was calculated from the main latitude and longitude channels, starting from the beginning of the cruise. M flags were applied automatically to the same cycles where the position data were interpolated.

Bathymetry (MBANZZ01)

Bathymetry data from both the echosounder and multibeam were loaded and screened. The multibeam bathymetry was almost entirely null so it was decided that the echosounder was a better source. M flags were applied to noisy data and cycles were values had dropped to zero were nullified and an appropriate flag was applied.

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: