Metadata Report for BODC Series Reference Number 1635041

• 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

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

Datawell Directional Waverider Buoy

General

The Datawell Datawell Directional Waverider is a 90cm diameter spherical buoy which measures wave height, period and direction. The directional measurement is based on a translational principle so that horizontal motions rather than wave slopes are measured. Consequently the measurement is independent of buoy roll motions and a relatively small spherical buoy may be used. A single point vertical mooring ensures adequate symmetrical horizontal buoy response to resolve small motions at low frequencies. Two 15m lengths of rubber cord are normally included in the mooring. Data are transmitted to a shore based station and/or an Argos satellite.

Sensors

• Heave-pitch-roll sensor Hippy40
• Three axis fluxgate compass
• Two fixed "x" and "y" accelerometers
• Temperature sensor

Principles of Measurement

The Directional Waverider measures vertical accelerations by means of an accelerometer placed on a gravity stabilised platform. This platform is formed by a disk which is suspended in the fluid within a plastic sphere placed in the bottom of the buoy. Two vertical coils are wound around the plastic sphere and one small horizontal coil is placed on the platform. The pitch and roll angles are defined by the amount of coupling between the fixed coils and the coil on the platform. This coupling is measured. The result of the measurement gives the sine of the angles between the coil axes (x and y axes) and the horizontal plane (=platform plane). The fluxgate compass measures the components of the Earth's magnetic field in the direction of the x, y and z axes. All of these measurements define the buoy's position with respect to fixed (north, south and vertical) coordinates.

A transformation matrix of the relation between vector components in buoy coordinates and fixed coordinates is formed. The acceleration of the buoy is measured in the x and y directions (two fixed accelerometers) and in the vertical direction (accelerometer mounted on a stabilised platform).

With the help of the transformation matrix and these measured accelerations, the accelerations in the north-south and east-west directions can be calculated. All the analogue outouts of the sensors are filtered using a low-pass filter with a cut-off frequency of 1.5Hz. At this frequency, the buoy's motions are already strongly attenuated due to the small wavelengths compared to the buoy's dimensions (geometric attenuation).

The filter outputs are sampled at a rate of 3.84Hz. As transformation calculations are performed at this rate by the on-board processor, the three accelerations are available at the same rate. By means of further digital processing, the acceleration data are filtered (low-pass 10th order filter with a cut-off at 0.6Hz) and double integrated to give three translation signals in the frequency range 0.033Hz - 0.6Hz (3dB) (0.05Hz - 0.55Hz 0.31dB). These translation signals are transmitted over the radio link in real time.

A complete spectrum is calculated every half hour. Parameters are calculated at each of 64 frequency points (0.025Hz - 0.100HZ at 0.005Hz intervals and 0.110Hz to 0.580Hz at 0.010Hz intervals). The parameters calculated at each frequecny point are: mean direction, angle of spread, second harmonics of angular energy distribution check factor and relative power density.

Reference

Datawell bv, Zomerlustraat 4, 2012 LM Haarlem, the Netherlands (1995). Operation and Service Manual for "Directional Waverider" from serial no. 30109 and including 30076, 30101, 30106, 30108.

BODC Processing

Data were received by BODC in Excel spreadsheets. These were then stabilised into text files and reformatted to QXF format using BODC transfer function 518. 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.

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 Ichthys Brunei Bay wave buoy deployment.

There was one wave survey at this site.

This directional waverider buoy was deployed in a water depth (defined as the Lowest Astronomical Tide) of 22 metres. (Nominal position of 14° 24.659'S, 124° 57.6671'E):

Related Data Activity activities are detailed in Appendix 1

Cruise

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:

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: Ichthys Brunei DWR

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.