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Metadata Report for BODC Series Reference Number 294801

Metadata Summary

Data Description

Data Category CTD or STD cast
Instrument Type
Neil Brown MK3 CTD  CTD; water temperature sensor; salinity sensor; dissolved gas sensors
Instrument Mounting research vessel
Originating Country United Kingdom
Originator -
Originating Organization University of Wales, Bangor School of Ocean Sciences (now Bangor University School of Ocean Sciences)
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) -

Data Identifiers

Originator's Identifier CH24/F640
BODC Series Reference 294801

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1988-02-06 14:12
End Time (yyyy-mm-dd hh:mm) -
Nominal Cycle Interval 1.0 metres

Spatial Co-ordinates

Latitude 57.16330 N ( 57° 9.8' N )
Longitude 6.66330 W ( 6° 39.8' W )
Positional Uncertainty Unspecified
Minimum Sensor or Sampling Depth 1.0 m
Maximum Sensor or Sampling Depth 154.0 m
Minimum Sensor or Sampling Height 16.0 m
Maximum Sensor or Sampling Height 169.0 m
Sea Floor Depth 170.0 m
Sea Floor Depth Source -
Sensor or Sampling Distribution Variable common depth - All sensors are grouped effectively at the same depth, but this depth varies significantly during the series
Sensor or Sampling Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
Sea Floor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface


BODC CODERankUnitsTitle
CNDCPR011Siemens per metreElectrical conductivity of the water body by in-situ conductivity cell
DEPHPR011MetresDepth below surface of the water body by profiling pressure sensor and converted to seawater depth using UNESCO algorithm
PSALPR011DimensionlessPractical salinity of the water body by conductivity cell and computation using UNESCO 1983 algorithm
TEMPST011Degrees CelsiusTemperature of the water body by CTD or STD

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

Problem Reports

No Problem Report Found in the Database

Data Access Policy

Public domain data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."

Narrative Documents

Neil Brown MK3 CTD

The Neil Brown MK3 conductivity-temperature-depth (CTD) profiler consists of an integral unit containing pressure, temperature and conductivity sensors with an optional dissolved oxygen sensor in a pressure-hardened casing. The most widely used variant in the 1980s and 1990s was the MK3B. An upgrade to this, the MK3C, was developed to meet the requirements of the WOCE project.

The MK3C includes a low hysteresis, titanium strain gauge pressure transducer. The transducer temperature is measured separately, allowing correction for the effects of temperature on pressure measurements. The MK3C conductivity cell features a free flow, internal field design that eliminates ducted pumping and is not affected by external metallic objects such as guard cages and external sensors.

Additional optional sensors include pH and a pressure-temperature fluorometer. The instrument is no longer in production, but is supported (repair and calibration) by General Oceanics.


These specification apply to the MK3C version.

Pressure Temperature Conductivity

6500 m

3200 m (optional)

-3 to 32°C 1 to 6.5 S cm-1

0.0015% FS

0.03% FS < 1 msec


0.003°C < 30 msec

0.0001 S cm-1

0.0003 S cm-1 < 30 msec

Further details can be found in the specification sheet.

RRS Challenger Cruise 24/88 CTD Data Documentation


Documentation for the CTD data collected on RRS Challenger Cruise 24/88 (3 December 1988 - 15 December 1988) by the School of Ocean Sciences, University College of North Wales, Menai Bridge, U.K., under the direction of J.H. Simpson.

Data Collection

The instrument used was a Neil Brown Instruments System Mark III CTD. Observed parameters were pressure, temperature and conductivity. The instrument was lowered as slowly as possible, at about 1 m/s. In general the CTD was lowered to within 5-10 metres of the seabed, except on some slope stations when a rising slope prevented this. The data were logged on a BBC microcomputer.


There were some rogue calibration data points. On examination these were found to have been collected in areas of strong temperature or salinity gradients and have been omitted from the statistics.


The temperature calibration readings were made using digital thermometers (RMT4002). These gave very good agreement with the CTD sensor.

Mean temperature difference
(digital thermometer - CTD)
Standard Deviation 0.003
Variance 0.000
No. of Points 60
Temperature Calibration CTD temperature + 0.000 (°C)


Water samples for salinity determinations were taken on most casts; on some casts, particularly the deeper ones, more than one calibration sample was taken.

Mean salinity difference
(Water sample - CTD)
Standard Deviation 0.0036
Variance 0.0000
No. of Points 135
Salinity Calibration CTD salinity + 0.0168 (PSU)


There was an offset of 1.7 decibars, i.e.

Pressure = CTD pressure - 1.7 (decibars)

Data Processing

The University's mainframe computer was used for processing the data, using an in-house Pascal CTD package. The data were checked for erroneous readings and the up and downcasts were averaged. The calibration details were applied and the data were processed into 1m depth bins.


Mitchelson-Jacob, E.G., Hill, A.E. and Simpson, J.H. 1989.
A report on the CTD data collected west of Scotland during the winter of 1987-88 as part of the Scottish Coastal Current and Autumnal Circulation Experiment (ACE) programmes. School of Ocean Sciences, University College of North Wales. January 1989.

Project Information

No Project Information held for the Series

Data Activity or Cruise Information


Cruise Name CH24
Departure Date 1988-02-03
Arrival Date 1988-02-15
Principal Scientist(s)John H Simpson (University of Wales, Bangor School of Ocean Sciences)
Ship RRS Challenger

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:

Flag Description
Blank Unqualified
< 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.)
D Thermometric depth
E End of CTD Down/Up Cast
G Non-taxonomic biological characteristic uncertainty
H Extrapolated value
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
N Null value
O Improbable value - user quality control
P Trace/calm
Q Indeterminate
R Replacement value
S Estimated value
T Interpolated value
U Uncalibrated
W Control value
X Excessive difference

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Flag Description
0 no quality control
1 good value
2 probably good value
3 probably bad value
4 bad value
5 changed value
6 value below detection
7 value in excess
8 interpolated value
9 missing value
A value phenomenon uncertain
Q value below limit of quantification