Metadata Report for BODC Series Reference Number 750796
No Problem Report Found in the Database
TOTAL GABON CTD Data Quality Report
The originator did not specify whether the salinity data were calibrated or uncalibrated.
Users are advised to use only the downcast data between the 'B' and 'E' flags, as the upcast data does not have any quality control flags.
The time channel was not provided and the duration of the measurement can be estimated as 20 minutes maximum considering that the maximum depth is equal to 225 m..
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.
Valeport Self Recording CTD Model 604
CTD Unit and Auxiliary Sensors
The Valeport Model 604 CTD measures pressure, temperature, conductivity and sound speed data.
|Conductivity||Pressure balanced inductive coils||0.1 to 60 mS/cm||±0.05 mS/cm||0.003 mS/cm||100 ms|
|Temperature||Fast PRT||-5 to +35 degC||± 0.02 degC||0.002 degC||100 ms (60 ms without guard)|
|Temperature [optional]||Slow PRT||-5 to +35 degC||±0.02 degC||0.002 degC||250 ms|
|Pressure||Strain Gauge||1000, 2000 or 3000 dBar||±0.1% FS||0.005% FS||20 ms|
|Salinity||Derived [SAL78]||±0.07 PSU||0.003 PSU|
|Speed of Sound||Derived [user selectable formula]||± 0.25 m/s||0.02 m/s|
|Density Anomaly Gamma||Derived [EOS80]||±00.06 kg/m3||0.01 kg/m3|
Further details can be found in the manufacturer's specification sheet
Data were received by BODC in comma separated value ASCII format files. These were reformatted to the internal QXF format using BODC transfer function 414. The following table shows how the variables within the file were mapped to the appropriate BODC parameter codes:
|Original parameter name||Original Units||Description||BODC Parameter Code||BODC Units||Comments|
|Temp||degrees Celsius||TEMPST01||degrees Celsius|
* The originator was not clear whether this measurement is pressure (db) or depth (m). The equation used to calculate the sound velocity (Medwin's formula) required depth in meters.
Approximate water depths were taken from the General Bathymetric Chart of Oceans (GEBCO), as they were not provided by the originator.
Following transfer to QXF, the data were screened using BODC's in-house visualisation software, EDSERPLO.
For all the series and in all the channels, the downcast was delimited by flagging 'B' the beginning of the down cast and 'E' the end of the down cast.
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.
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.
Complete Cruise Metadata Report is available here
No Fixed Station Information held for the Series
The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:
|<||Below detection limit|
|>||In excess of quoted value|
|A||Taxonomic flag for affinis (aff.)|
|B||Beginning of CTD Down/Up Cast|
|C||Taxonomic flag for confer (cf.)|
|E||End of CTD Down/Up Cast|
|G||Non-taxonomic biological characteristic uncertainty|
|I||Taxonomic flag for single species (sp.)|
|K||Improbable value - unknown quality control source|
|L||Improbable value - originator's quality control|
|M||Improbable value - BODC quality control|
|O||Improbable value - user quality control|
|0||no quality control|
|2||probably good value|
|3||probably bad value|
|6||value below detection|
|7||value in excess|
|A||value phenomenon uncertain|
|Q||value below limit of quantification|