Metadata Report for BODC Series Reference Number 41331

Metadata Summary

Data Description

Data Category Offshore sea floor pressure series
Instrument Type Tide gauge (unspecified)
Instrument Mounting fixed benthic node
Originating Country United Kingdom
Originator -
Originating Organization Institute of Coastal Oceanography and Tides (now National Oceanography Centre, Liverpool)
Processing Status banked
Project(s) -

Data Identifiers

Originator's Identifier M2SPC/PDFH4
BODC Series Reference 41331

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1972-07-16 02:07
End Time (yyyy-mm-dd hh:mm) 1972-08-17 13:51
Nominal Cycle Interval 900.0 seconds

Spatial Co-ordinates

Latitude 36.67660 N ( 36° 40.6' N )
Longitude 14.24490 W ( 14° 14.7' W )
Positional Uncertainty 0.1 to 0.5 n.miles
Minimum Sensor Depth 212.0 m
Maximum Sensor Depth 212.0 m
Minimum Sensor Height 0.0 m
Maximum Sensor Height 0.0 m
Sea Floor Depth 212.0 m
Sensor Distribution Fixed common depth - All sensors are grouped effectively at the same depth which is effectively fixed for the duration of the series
Sensor 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 CODE Rank Units Short Title Title
AADYAA01 1 Days Date(Loch_Day) Date (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ01 1 Days Time(Day_Fract) Time (time between 00:00 UT and timestamp)
PPSSRL01 1 Decibars RelBotPress Pressure (measured variable) exerted by the water body by fixed in-situ pressure sensor and corrected using co-located air pressure data expressed to unspecified datum by subtraction of a constant

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

Type 1 Off-Shore Tide Gauge

This instrument was developed at I.O.S. Wormley. It incorporates a seabed mounted pressure transducer interfaced to a 12 channel Normalair-Garret data logger housed in a 56cm diameter aluminium pressure sphere. The frequency modulated (FM) transducer consists of a diaphragm which when flexed by changing hydrostatic pressure varies the gap of a parallel plate timing capacitor in an LC oscillator circuit. The pressure casing enclosing the transducer circuitry is evacuated so that absolute rather than relative pressure is measured. The frequency output is divided down to about 100Hz and is counted over a period of 890 seconds to average out the unwanted fluctuations due to waves: this sampling period gives 50dB (99.999 p. cent) attenuation of energy from 10 second period waves, but only 0.006dB (0.14 p. cent) attenuation of semi diurnal tidal energy.

The integration period of 890 seconds and the subsequent 10 second scanning and recording sequence are controlled by 900 second pulses from a crystal clock. The reading from each channel is recorded serially in either 3 or 4 decade BCD on 0.25 inch magnetic tape and a parity bit is added during each scan by the digital serializer. A synchronizing signal is recorded on a second track of the tape to assist in translating the magnetic tape during the data processing.

The sphere containing the data logger and interfacing electronics is mounted in a tripod frame made of tubular steel with the pressure transducer mounted on the base of the framework and beneath the sphere. The tripod is supported on a disposable heavy ballast frame consisting of welded girders and the two frames are connected by 3 corrodible magnesium alloy links and a pyrotechnic release mechanism. The recorders are deployed as pop up moorings and released by acoustic release.

Data Processing Notes

Clock gained 56 seconds over 32 days 11 hours 44 minutes 4 seconds; the cycle interval and time values have been corrected.

Instrument Characteristics

Station M2

OSTG Mark I Number 5
Sensors OSC 1/2 (BODC Series Ref. 41331)
FM HEAD 22 no data available
Nominal sampling interval 900 seconds
Integration period 890 seconds

IOS Data Processing of Off-Shore Pressure Recorder Data

Data processing comprises 2 stages:-

  1. Instrumental drift and depth are removed, thus the drift free series is produced with an artificial mean of zero.

  2. Generally the pressure values have been obtained by integration and averaging over the sampling interval, followed by logging; hence the time value assigned to a data cycle has been chosen as the mid-point between the start and end time of each interval. Some pressure records have been sample rate reduced from the basic time step of the recorder to produce either hourly or 15 minute values, incorporating any timing corrections due to clock error.

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