Metadata Report for BODC Series Reference Number 1749246

• 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

UK Ocean Acidification RRS Discovery Cruise D366 Underway Navigation and Bathymetry Data Quality Report

Navigation

The navigation data channels (ALATGP01 and ALONGP01) have been through BODC quality control screening. Three gaps of less than ten minutes have been filled by interpolation. Overall the data for the cruise duration appear good.

Bathymetry

The bathymetric data channel has been through BODC quality control screening. There are extensive periods of large-scale noise that hide the real bathymetry in the channel. Where possible some periods have been flagged to remove the noise. Users should use caution when interpreting the bathymetric depth channel.

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.

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.

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.

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.

Trimble 4000DS Global Positioning System receiver

The Trimble 4000DS Differential Surveyor is similar to the 4000RS (a Maxwell-based receiver that is oriented toward precision positioning applications. It is intended for use as a DGPS base station, generating RTCM-104 corrections). The 4000Ds can apply RTCM-104 corrections to the satellite data it receives in order to generate accurate position fixes in real time.

UK Ocean Acidification RRS Discovery Cruise D366 Underway Navigation and Bathymetry Instrumentation

The instruments used to collect the navigation and bathymetry datasets are displayed in the table below.

UK Ocean Acidification RRS Discovery Cruise D366 Underway Navigation and Bathymetry Data Processing Document

Originator's Data Processing

During the cruise there was a dual logging system in place on the RRS Discovery. Data from the various instruments were logged to the RVS Level-C system (Sun Solaris 10 UNIX Workstation discovery1) and also as NetCDF (binary) through the Ifremer Techsas data logging system.

Processing was carried out using the RVS software suite. The following routines were run on the navigation and bathymetry data channels to produce files named after the routine that generated them:

• RELMOV - Relmov is the relative motion file for this cruise. This was generated using the ships gyro and ships Chernikeef Log data to extract a movement in a given direction. This was then used by bestnav when and where necessary to calculate fixes if GPS fixes were not available.

• BESTNAV - Bestnav uses all 3 GPS Systems logged and creates a best suite stream by providing an as complete account of the ships track as possible. This is done by reading all 3 GPS streams with gps_g2 being primary, gps_4000 as secondary and gps_ash as tertiary. The system looks for gaps of a certain length in the primary and when it finds those gaps it requests that the next gps down fill in the gaps. If no GPS data is available it asks RELMOV to fill in until data is available again. Then the system calculates back over itself to ensure that the extrapolated positions are correct using the GPS data available around the gap.

• BESTDRF - Bestdrf is a product of bestnav. When run bestnav uses the relmov data which contains a predicted vn and ve based upon direction and speed through the water. The Bestdrf file is the accurate drift velocity of what actually occurred based on the GPS changes between each record.

• PRODEP - Prodep is an automated process that accessed the bestnav position fix data and then uses a pre programmed Carter tables of corrections and corrects the echo sounder data for that given time.

Files delivered to BODC

BODC Data Processing

Reformatting

The RVS files were transferred into internal BODC format by merging the files into a single binary file using time as the primary linking key. The time span of the file was from 06/06/2011 08:08:50 to 09/07/2011 12:55:50, with a sampling interval of 60 seconds.

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

gyro

bestnav

prodep

Screening

Each data channel was inspected on a graphics workstation and any spikes or periods of dubious data were flagged. The power of the workstation software was used to carry out comparative screening checks between channels by overlaying data channels. A map of the cruise track was simultaneously displayed in order to take account of the oceanographic context.

Data Processing

Navigation channels

Both the bestnav and gp_g2 data channels were transferred to BODC format and comparison of the channels indicated the bestnav channel was of better quality. The bestnav navigation channels were checked using BODC Matlab routine 'navcheck' and one gap of nine minutes was identified. The gap was removed by interpolating the data using BODC Matlab routine 'navint'. There were no speed check failures. The latitude (ALATGP01) and longitude (ALONGP01) channels were screened though no further flags were applied.

Velocity and distance run channels

The north-south (APNSGP01) and east-west (APEWGP01) ship's velocities were calculated from the latitude and longitude using the BODC Matlab routine 'velcal'. Distance run (DSRNCV01) was then calculated using the BODC Matlab routine 'disrun'.

Calibrations

No calibration against sample data or manufacturer's calibrations were applied to the navigation channels.

Project Information

UKOARP Theme B: Ocean acidification impacts on sea surface biology, biogeochemistry and climate

The overall aim of this theme is to obtain a quantitative understanding of the impact of ocean acidification (OA) on the surface ocean biology and ecosystem and on the role of the surface ocean within the overall Earth System.

The aims of the theme are:

• To ascertain the impact of OA on planktonic organisms (in terms of physiological impacts, morphology, population abundances and community composition).
• To quantify the impacts of OA on biogeochemical processes affecting the ocean carbon cycle (both directly and indirectly, such as via availability of bio-limiting nutrients).
• To quantify the impacts of OA on the air-sea flux of climate active gases (DMS and N₂O in particular).

The main consortium activities will consist of in-situ measurements on three dedicated cruises, as well as on-deck bioassay experiments probing the response of the in-situ community to elevated CO₂. Most of the planned work will be carried out on the three cruises to locations with strong gradients in seawater carbon chemistry and pH; the Arctic Ocean, around the British Isles and the Southern Ocean.

Weblink: http://www.oceanacidification.org.uk/research_programme/surface_ocean.aspx

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: