Metadata Report for BODC Series Reference Number 1052443

• 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 Total Angola Block 32 Tide Gauge Data Narrative

Narrative

Aanderaa WLR8 water level recorders were deployed on the Louro and Canyon moorings, offshore Angola.

Data Quality Information

The tide data from both moorings have gaps starting on April 21st 2011. The gap ends at the Louro site on April 23rd 2011 with an apparent datum shift of approximately 0.4 metres. The gap ends at the Canyon site on April 24th 2011 with an apparent datum shift of approximately 0.2 metres. For the remainder of the record, there is a a drift back to the pre-shift levels. It is possible that either both moorings were repositioned, or that there were differences in the pre-processing of the data before and after April 21st 2011. As a result, the quality of this tide data should be considered as quite poor.

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

Aanderaa Water Level Recorder - WLR8

As with the WLR models 5, 6 and 7, the WLR8 is a self-contained, high precision instrument for recording of the water level by precise measurement of hydrostatic pressure. The WLR8 is specifically designed to measure ocean water levels in deep seas. It has a pressure case which is able to operate down to 6,000 meters. The pressure sensor consists of an oscillating quartz crystal which shifts frequency with the force applied to it. Temperature is measured by a Fenwall thermistor.

The data from the WLR8 are stored in a solid-state data storage unit which can store up to 65,500 ten bit, PDC-4 coded words in a set of EEPROMs.

Specifications

Measuring System

A digital system based on counting pulses from a sensor with frequency output. Five channels are measured in sequence and a ten-bit binary word is produced for each channel.

Pressure

Temperature

The thermistor is a Fenwall GB32JM19

Conductivity

Conductivity Cell 4094 is used.

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

BODC Processing

Data were received by BODC in ASCII format files (Fugro format). They were reformatted to QXF format using BODC transfer function 400. The following table shows how the variables within the files were mapped to the appropriate BODC parameter codes:

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

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.

Data Activity or Cruise Information

Data Activity

SIMORC Total Canyon Current Meter and ADCP mooring.

The survey at this site was made up of a single mooring.

This mooring was deployed in a water depth of 1795 metres. (Nominal position of 7.40007°S 11.259305°E):

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Total - Angola Block 32 - Canyon

This fixed station is in Block 32, offshore Angola. A mooring was deployed at this site in January 2009 to cover a 12-month period of measurements of currents through the water column. Prior to the mooring deployment, a CTD dip was undertaken to check the actual water depth.

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: Canyon

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: Canyon, Angola Block 32

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.