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Metadata Report for BODC Series Reference Number 33748

Metadata Summary

Data Description

Data Category Offshore sea floor pressure series
Instrument Type
Institute of Oceanographic Sciences MkII bottom pressure recorder  sea level recorders
Instrument Mounting fixed benthic node
Originating Country United Kingdom
Originator -
Originating Organization Institute of Oceanographic Sciences Bidston Laboratory (now National Oceanography Centre, Liverpool)
Processing Status banked
Online delivery of data Download available - Ocean Data View (ODV) format
Project(s) JONSDAP 1973

Data Identifiers

Originator's Identifier 735/973/251
BODC Series Reference 33748

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1973-09-08 12:07
End Time (yyyy-mm-dd hh:mm) 1973-10-21 11:51
Nominal Cycle Interval 900.0 seconds

Spatial Co-ordinates

Latitude 52.45160 N ( 52° 27.1' N )
Longitude 3.24160 E ( 3° 14.5' E )
Positional Uncertainty 0.1 to 0.5 n.miles
Minimum Sensor or Sampling Depth 35.0 m
Maximum Sensor or Sampling Depth 35.0 m
Minimum Sensor or Sampling Height 0.0 m
Maximum Sensor or Sampling Height 0.0 m
Sea Floor Depth 35.0 m
Sea Floor Depth Source -
Sensor or Sampling Distribution Fixed common depth - All sensors are grouped effectively at the same depth which is effectively fixed for the duration of 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
AADYAA011DaysDate (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ011DaysTime (time between 00:00 UT and timestamp)
PRSTPS011DecibarsPressure (measured variable) exerted by the water body plus atmosphere by fixed in-situ pressure sensor

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

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

IOS Off-Shore Pressure Recorder Mark II

This instrument was developed by Marconi Space and Defence Systems Limited in conjunction with I.O.S. Bidston. The data logger can sample a maximum of 20 input channels at periodic intervals and record their values by means of an incremental tape recorder in a computer compatible format. Any input channel is capable of sampling either D.C. or frequency modulated A.C. inputs - the FM inputs can be sampled for periods of 15/64, 15/16, 3.75, 15 or 60 seconds or continuously (i.e. the integrating time is virtually equal to the sampling period of the data from the channels).

The number of channels scanned can be truncated to less than 20 and the sampling interval can be 1.875, 3.75, 7.5, 15, 30 or 60 minutes. Sensor packs used with the logger incorporate both a pressure and a temperature sensor and are completely self contained units with their own sensor electronics and power supplies. Different types of pressure sensor based on either strain gauge, vibrating wire or quartz crystal systems have been used on the tide gauge. A brief description of each is given below.

  1. The strain gauge sensor has been developed using a Bell and Howell type 4-306 transducer and operates as a phase shift oscillator whose frequency is controlled by the ratio of output to input voltage of the transducer Wheatstone bridge network.

  2. The vibrating wire sensor consists of a tungsten wire stretched between a rigid frame and a diaphragm and mounted in a magnetic field. Any movement of the diaphragm due to a change of pressure will increase or decrease the tension of the wire and hence change its natural frequency of oscillation. The wire is connected in the feedback loop of an amplifier and thus makes a variable frequency oscillator where frequency is a function of pressure. To achieve temperature compensation for the coefficient of expansion of the wire, the coefficient of expansion of the supporting frame is designed to balance the expansion of the wire. These sensors are manufactured by Vibroton and Ocean Applied Research.

  3. Two types of quartz crystal pressure sensor have been used. The Digiquartz pressure sensor consists of a convoluted bellow linked to a 40kHz quartz crystal resonator coupled by piezoelectric action to an electronic resonator. The Hewlett Packard Oceanographic sensor consists of a 5MHz quartz resonator coupled by piezoelectric action to an electronic oscillator and mounted in an oil filled case adjacent to a pressure case containing the electronic circuitry. A second closely matched quartz crystal resonator is mounted in the pressure case and is therefore not exposed to hydrostatic pressure and is used for temperature compensation by heterodyning the frequency outputs of the two crystals.

The data logger and batteries are housed in a 56cm diameter aluminium sphere with sufficient space for the sensor batteries, acoustic release electronics and ancillary sensor electronics. The sphere and a number of sensor packs are mounted in an aluminium sub-frame which in turn is protected by a heavy steel outer frame. The Mk II tide gauge is usually deployed using a U-shaped mooring (i.e. buoy or pellet float to wire rope to tide gauge to ground line to anchor to wire rope to buoy), but W-shaped moorings are used in conjunction with either current meters or thermistor chains. A W-shaped mooring comprises pellet float to pellet line to sub- surface buoy to current meter or thermistor line to anchor weight to ground line to tide gauge to ground line to anchor weight to wire rope to surface buoy.

IOS Calibration and Data Processing of Off-Shore Tide Gauge Data

Calibration of pressure/frequency sensors and thermistors are carried out using the facilities and staff at I.O.S. Bidston with the exception of pre 1975 pressure/frequency sensors, which were calibrated in the pressure chamber at I.O.S. Wormley.

The data are copied from the logger magnetic tape to 9 track magnetic tape and disk. The data are either listed or plotted as an initial check. A program is then used to check the data from the temperature sensor channels, calculate and plot the temperature values and store them (if temperature sensor channels are available).

A second program performs a similar function for the pressure sensor channel, using the pressure frequency coefficient to convert each pressure frequency to the frequency at the reference temperature and calculating the pressures using the pressure frequency calibration. The data values, generally at 15 minute intervals, but occasionally at 10 minute intervals, of pressure are then plotted and stored. If waterhead is required, it may be computed by subtracting atmospheric pressure and applying the hydrostatic relation:-

H = P / ( d * g )
H = waterhead (cm)
P = pressure (0.01 mb)
d = density (kg/m3)
g = gravitational acceleration (m/s2)

Station WE (Southern North Sea) Data Processing Notes

Clock gained 6 seconds over 58 days, 23.25 hours; the cycle interval and time values have been corrected.

Instrument characteristics and calibration factors

OSTG Mk II, logger 02, sensor VIB 1/3
Original sampling interval 15 minutes
Integration period 900s
Temperature coefficient 11.3cm/°C
Pressure sensitivity at 14.9°C 0.036Hz/cm

To convert pressure to elevation the following values should be used:

Density (from CTD casts) 1025.48kg/m3
Gravitational acceleration constant 9.813m/s2

Large sandwave in vicinity of OSTG position on launch.

Project Information

Joint North Sea Data Acquisition Project for 1973 (JONSDAP 73)

This was the second phase of the cooperative data collection programme JONSDAP which was begun in 1970 by the countries bordering the North Sea. This phase, JONSDAP 73, was a programme of tide and current measurement in the Southern Bight of the North Sea from September to October 1973.

Other JONSDAP exercises

The first JONSDAP achieved the systematic collection of data from moored stations and coastal observation sites in the North Sea in the period 1971 to 1973. The third, JONSDAP 76, consisted of two intensive measurement programmes:

  1. FLEX, the Fladen Ground Experiment, to study the development of the thermocline and the dynamics of the plankton bloom.
  2. INOUT, concerned with the general circulation of the North Sea and the storm surge problem.

Data Activity or Cruise Information

No Data Activity or Cruise Information held for the Series

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
B nominal value
Q value below limit of quantification