Metadata Report for BODC Series Reference Number 1759855

• 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 Discovery D381A and D381B navigation quality control report

No data quality issues concerning navigation were found. (BODC assessment)

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

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.

RRS Discovery D381A and D381B navigation instrumentation

Instrumentation

The following scientific navigational and bathymetric systems were fitted.

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 Discovery D381A and D381B navigation processing procedures

Originator's Data Processing

The following is adapted from the Discovery 381 cruise report.

Navigation

The ship's primary position instrument is a Fugro SeaStar 9200G2 system. For cruise D381, the backup system was the Ashtech ADU5 3-D GPS system. Using the Fugro SeaStar 9200G2 system as its primary navigation source, the NMFSS Bestnav combined (10 second) cleaned navigation process was operational and working well.

Navigation and gyro data were transferred regularly from the RVS format file streams to pstar navigation files, e.g. abnv38102, gpC38101, gyr38101 or ash38101. The navigation file for the entire first leg was abnv38101 while the respective file for the second leg was abnv38102. The gpC data file for the first leg was gpC3811 while the file for the second leg was gpC3812. The gyro file for the first leg was gyr38101 while for the second leg it was gyr38102. The ashtech file for the first leg was ash38101 while for the second leg they were labelled in sequence as ash38102, ash38103 and so on. The latter each correspond to about one day's worth of data.

Processing scripts nav-, gyro-, gps-exec0 are summarized below:

• navexec0 transferred data from the RVS bestnav stream to PSTAR, calculated the ship's velocity, appended onto the absolute (master) navigation file and calculated the distance run from the start of the master file. Output: abnv3811, abnv3812.
• gyroexec0 transferred data from the RVS gyro stream to Pstar, a nominal edit was made for directions between 0-360° before the file was appended to a master file. Output: gyr38101, gyr38102.
• gpCexec0 transferred data from the RVS gps g2 stream to Pstar, edited out pdop (position dilution of precision) greater than 7 and appended the new file to a master file. The master file was averaged to create an additional 30 second file and distance run was calculated and added to both.

Heading

The ships attitude was determined every second with the ultra short baseline 3D GPS Ashtech ADU5 navigation system. The Ashtech data were used to calibrate the gyro heading information as follows:

• ashexec0 transferred data from the RVS format stream gps ash to pstar.
• ashexec1 merged the ashtech data from ashexec0 with the gyro data from gyroexec0 and calculated the difference in headings (hdg and gyro-Hdg); ashtech-gyro (a-ghdg).
• ashexec2 edited the data from ashexec1 using the following criteria:
• heading 0 < hdg < 360 (degrees) pitch -5 < pitch < 5 (degrees) roll -7 < roll < 7 (degrees) measurement RMS error 0.00001 < mrms < 0.01 baseline RMS error 0.00001 < brms < 0.1 ashtech-gyro heading -10 < a-ghdg < 10 (degrees)

The heading difference (a-ghdg) was then filtered with a running mean based on 5 data cycles and a maximum difference between median and data of 1 degree. The data were then averaged to 2 minutes and further edited for:

-2 < pitch < 2 0 < mrms < 0.004

The 2 minute averages were merged with the gyro data files to obtain spot gyro values. The ship's velocity was calculated from position and time, and converted to speed and direction. During ship manoeuvres, bad weather or around data gaps, there were spikes which were edited out manually (plxyed).

Files delivered to BODC

BODC Data Processing

Data were banked at BODC following standard banking procedures. During reformatting the data were split into two files for the two legs of the cruises D381A and D381B.

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

Screening

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). No gaps or improbable values were identified.

Ship Velocities

Ship velocities were calculated from the main latitude and longitude channels using standard BODC procedures.

Distance Run

Distance run was calculated from the main latitude and longitude channels, starting from the beginning of the file, using BODC standard procedures.

Calibration

No field calibrations have been applied to the data at BODC.

Project Information

Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study (OSMOSIS)

Background

The Ocean Surface Mixing, Ocean Sub-mesoscale Interaction Study (OSMOSIS) consortium was funded to deliver NERC's Ocean Surface Boundary Layer (OSBL) programme. Commencing in 2011, this multiple year study will combine traditional observational techniques, such as moorings and CTDs, with the latest autonomous sampling technologies (including ocean gliders), capable of delivering near real-time scientific measurements through the water column.

The OSMOSIS consortium aims to improve understanding of the OSBL, the interface between the atmosphere and the deeper ocean. This layer of the water column is thought to play a pivotal role in global climate and the productivity of our oceans.

OSMOSIS involves collaborations between scientists at various universities (Reading, Oxford, Bangor, Southampton and East Anglia) together with researchers at the National Oceanography Centre (NOC), Scottish Association for Marine Science (SAMS) and Plymouth Marine Laboratory (PML). In addition, there are a number of project partners linked to the consortium.

Scientific Objectives

• The primary goal of the fieldwork component of OSMOSIS is to obtain a year-long time series of the properties of the OSBL and its controlling 3D physical processes. This is achieved with an array of moorings (two nested clusters of 4 moorings, each centred around a central mooring) and gliders deployed near the Porcupine Abyssal Plain (PAP) observatory. Data obtained from this campaign will help with the understanding of these processes and subsequent development of associated parameterisations.
• OSMOSIS will attempt to create parameterisations for the processes which determine the evolving stratification and potential vorticity budgets of the OSBL.
• The overall legacy of OSMOSIS will be to develop new (physically based and observationally supported) parameterisations of processes that deepen and shoal the OSBL, and to implement and evaluate these parameterisations in a state-of-the-art global coupled climate model, facilitating improved weather and climate predictions.

Fieldwork

Three cruises are directly associated with the OSMOSIS consortium. Preliminary exploratory work in the Clyde Sea (September 2011) to hone techniques and strategies, followed by a mooring deployment and recovery cruise in the vicinity of the Porcupine Abyssal Plain (PAP) observatory (in late Summer 2012 and 2013 respectively). Additional opportunist ship time being factored in to support the ambitious glider operations associated with OSMOSIS.

Instrumentation

Types of instrumentation and measurements associated with the OSMOSIS observational campaign:

• Ocean gliders
• Wave rider buoys
• Towed SeaSoar surveys
• Microshear measurements
• Moored current meters, conductivity-temperature sensors and ADCPs
• Traditional shipboard measurements (including CTD, underway, discrete nutrients, LADCP, ADCP).

Contacts

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: