Metadata Report for BODC Series Reference Number 749758

• 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

SIMORC Data Quality Report: Angola Block 17 Current PH1_300

Direction data are noisy on the 21-23 June 2002, on the 13 July 2002 and on the 6- 8 Aug 2002 (it seems to be the same in all the water column). For bin 20, the speed is noisy. Speed data appears to be of good quality.

Data Access Policy

SIMORC data access conditions

The data collated and held at BODC on behalf of the SIMORC project are restricted. However, the data will be available to download from the Official SIMORC Website, as part of the project protocol. The data set will initially include data from the oil companies TOTAL, Shell and BP.

Narrative Documents

RD Instruments 300kHz Workhorse Sentinel Acoustic Doppler Current Profiler

Specifications

The manufacturer's specification document can be found here

BODC Processing

Data were received by BODC in ASCII format files. These were reformatted to the internal QXF format using BODC transfer function 409. The following table shows how the variables within the file were mapped to the appropriate BODC parameter codes:

Following transfer to QXF, the data were screened using BODC's in-house visualisation software, EDSERPLO.

Originator processing notes

TOTAL Angola Girassol C50247/2827/R1, current processing

The raw RDI binary data files provided were subjected to Fugro GEOS standard rigorous quality control procedures. The main features of the routine ADCP data quality control procedures are outlined in this section. Quality control procedures applied to both instruments from both phases during post processing included but were not limited to the following:

• Production of quality control plots to inspect the general quality of the data and evaluate the effectiveness of each individual quality control procedure.
• Preliminary quality control including the error-flagging of records with current speeds less than 0.0m.s^-1.
• Error-flagging of records with less than 25% good pings.
• False start and end times were applied to the data sets to remove invalid data recorded during instrument deployment and recovery.

Both instruments from both phases were subject to inspection of data quality by an experienced oceanographer in order to identify and manually remove any remaining anomalous values. Only one such spike was removed.

Extra processing for phase 1 to 3:

• Application of the magnetic declination of 6.17°W.
• 75kHz ADCP data from both phases and 300kHz ADCP data from phase 1 were error-flagged where error velocity exceeded 0.08m.s^-1 or fell below -0.08m.s^-1. Limits of 0.02m.s^-1 and -0.08m.s^-1 were applied to the 300kHz ADCP data from phase 2. Different limits were required due to a negative bias in the measured error velocity at all depth levels. This may be due to inhomogeneous characteristics of the water column or an instrument fault, but the measured data appeared reliable. In practice very little invalid data were removed on the basis or error velocity, which was generally clean for both instruments during both phases.
• 300kHz ADCP data from both phases was error-flagged where vertical velocity exceeded 0.03m.s^-1 or fell below -0.03m.s^-1.

Extra processing for phase 4 to 6:

• Application of the magnetic declination of 6.2°W.
• 75kHz BB ADCP data from Phase 4 and 300kHz WH ADCP data from all phases were error-flagged where error velocity exceeded 0.08ms-1 or fell below -0.08ms-1.
• Overlaid plots of echo amplitude and current speed were inspected but no evidence was found of a suspected contamination of horizontal velocities by the movement of biological scatterers.

The Fugro GEOS data at all available measurement depths were loaded into MATLAB for preparation. Gaps in the data were then filled by linear interpolation.

All interpolation was linear and performed on two orthogonal velocity components, as this is considered more appropriate than interpolation of speed and direction separately. The interpolation was performed in stages so that the consequences could be carefully assessed. This interpolation successfully filled all gaps in the data except those associated with service visits.

The data from the 300kHz and 75kHz ADCPs were recorded at 10-minute and 30-minute intervals respectively. Data have been splined onto a regular time base.

General Data Screening carried out by BODC

BODC screen both the series header qualifying information and the parameter values in the data cycles themselves.

Header information is inspected for:

• Irregularities such as unfeasible values
• Inconsistencies between related information, for example:
  • Times for instrument deployment and for start/end of data series
  • Length of record and the number of data cycles/cycle interval
  • Parameters expected and the parameters actually present in the data cycles
• Originator's comments on meter/mooring performance and data quality

Documents are written by BODC highlighting irregularities which cannot be resolved.

Data cycles are inspected using time or depth series plots of all parameters. Currents are additionally inspected using vector scatter plots and time series plots of North and East velocity components. These presentations undergo intrinsic and extrinsic screening to detect infeasible values within the data cycles themselves and inconsistencies as seen when comparing characteristics of adjacent data sets displaced with respect to depth, position or time. Values suspected of being of non-oceanographic origin may be tagged with the BODC flag denoting suspect value; the data values will not be altered.

The following types of irregularity, each relying on visual detection in the plot, are amongst those which may be flagged as suspect:

• Spurious data at the start or end of the record.
• Obvious spikes occurring in periods free from meteorological disturbance.
• A sequence of constant values in consecutive data cycles.

If a large percentage of the data is affected by irregularities then a Problem Report will be written rather than flagging the individual suspect values. Problem Reports are also used to highlight irregularities seen in the graphical data presentations.

Inconsistencies between the characteristics of the data set and those of its neighbours are sought and, where necessary, documented. This covers inconsistencies such as the following:

• Maximum and minimum values of parameters (spikes excluded).
• The occurrence of meteorological events.

This intrinsic and extrinsic screening of the parameter values seeks to confirm the qualifying information and the source laboratory's comments on the series. In screening and collating information, every care is taken to ensure that errors of BODC making are not introduced.

Project Information

System of Industry Metocean data for the Offshore and Research Communities (SIMORC)

The EU-funded SIMORC project is a collaborative effort between MARIS (Netherlands), BODC (UK), the International Association of Oil and Gas Producers (OGP) and IOC-IODE to provide a harmonised and quality controlled metocean data set from data collected by oil and gas producers, accessible through the SIMORC protocol.

ELF EXPLORATION ANGOLA, offshore ocean monitoring, Block 17

ELF ANGOLA required ocean monitoring services from March 2001 to July 2004. MeteoMer measured the following parameters :

• Waves (Directional Datawell waverider)
• Motion of the Floating Production, Storage and Offloading (FPSO) vessel (Hippy 80 - Datawell)
• Motion of the Single Buoy Mooring (Hippy 80 - Datawell)
• Wind of the FPSO (VAISALA Marine Automated Weather Station)
• Current profiles (ADCP RDI 300 khz and 75 khz)

Data Activity or Cruise Information

Data Activity

SIMORC: TOTAL Data, Angola, Block 17, ADCP Current 22/05/2002 - 21/08/2002 Data Activity

This site is part of the Total facility.

The generic position of the site is 7.6985 °S, 11.65383 °E with a water depth of 1500 m.

6 current moorings, consisting of 2 or 1 ADCP, were deployed during this study.

This particular mooring has been set from a vessel by Meteomer on behalf of Total in the Angola Block 17 Girassol and consisted of the following ADCPs.

For details of the 5 other moorings refer to series: 749783, 749802, 749826, 749851, 749863.

Related Data Activity activities are detailed in Appendix 1

Fixed Station Information

Fixed Station Information

SIMORC: Total Angola, Block 17 Girassol, Fixed Station Document

This site is part of the Total facility.

The moorings deployed lie within a box bounded by co-ordinates 7.7° S, 11.65° E at the southwest corner and 7.67° S, 11.6825° E at the northeast corner.

The GIRASSOL platform, Block 17, offshore Angola consists of a Floating Production, Storage and Offloading vessel (FPSO) and a Single Buoy Mooring (SBM).

Various deployments were taken from or near this station over a number of years.

Between September 1997 and October 1998

A current meter mooring occupied this site. In addition to time series data obtained from the moored instruments, CTD profiles were conducted following the deployment and prior to the recovery of the mooring to be used for calibration purposes.

Between March 2001 and July 2004

Wind, current and wave data have been collected on behalf of Total on the Girassol field.

Related Fixed Station activities are detailed in Appendix 2

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: SIMORC TTL Angola Block17 ADCP May 2002

Related series for this Data Activity 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.

Appendix 2: ANGOLA GIRASSOL

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.