Metadata Report for BODC Series Reference Number 953354

• 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

CH69 Sea surface navigation data quality report

Navigation was predominantly based on Decca and is hence prone to the inherent weaknesses in this system, particularly at dawn and dusk.

It should also be noted that no tidally corrected navigation data is available until 13:14:30 27/07/1990.

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

Kongsberg Simrad EA500 bathymetric echosounder

The EA500 is a bathymetric echosounder that can be used in water as deep as 10,000 m. It features triple frequency operation with a separate digitiser for each channel and high transmitted power with an instantaneous dynamic range of 160 dB. The instrument can operate with several pulses in the water simultaneously and has bottom tracking capabilities. A wide range of transducers (single beam, split beam or side-looking) is available and the ping rate is adjustable up to 10 pings per second. The split beam operation measures the athwartships inclination angle of the seabed.

This instrument was introduced in June 1989 and and replaced by the EA 600 in 2000.

Specifications

Further details can be found in the manufacturer's specification sheet.

Decca Navigator System

The Decca Navigator System (DNS) was a hyperbolic radio navigation system that operated by measuring the phase differences between continuous signals from master and slave stations. The differences were then related to hyperbolic lines printed on a chart (also known as lines of lattice). By plotting the readings from two pairs of hyperbolas at any particular instant, the user was able to plot their position instantly. The system operated from WWII until the UK transmitters were switched off at the end of March 2000.

The DNS consisted of groups of at least three shore based transmitter stations (or chains) which comprised one Master and two or three slave stations, usually located 80 to 110 km from the master station and positioned about 120° apart. The accuracy of this system depended on the distance to the baseline, time of day and seasonal effects.

The table below presents the general specifications for this system.

Specifications

Further details can be found here.

CH69 Sea surface navigation instrument details

Navigation was conducted by a Decca system and bathymetric depth was measured using a Simrad echo sounder with the transducer. Instrument details are given in the table below.

CH69 Sea surface Hydrography, Meteorology and Navigation Series

Instrumentation

A suite of parameters were logged from the non-toxic supply, the intake for which was located on the ship's hull, about 2m below the surface.

Operational procedure and data logging

Data were logged by the Research Vessels Services ABC data logging system. The data output units were sampled every 30 seconds by a microprocessor interface (the Level A) which passed time stamped data cycles to a Sun workstation (the Level C) via a buffering system (the Level B). Navigation was updated every two minutes and infilled by linear interpolation. Dissolved oxygen and probe temperature were logged at 15 minute intervals by a PC connected to the Endico controller and transferred to the Level C on floppy disk.

Data Processing

The raw data comprised ADC counts. These were converted into engineering units (degrees for latitude/longitude, volts for PAR meters, fluorometer, transmissometer and nutrients, mmho/cm for conductivity, degC for temperature, metres for bathymetry) by the application of laboratory determined calibrations and salinity was calculated using the algorithm in Fofonoff and Millard (1983). The data were submitted to BODC in this form.

CH69 Underway Navigation Series Processing Notes

Positional Data

Gaps when the Decca system was down or radio reception was too poor were infilled using SatNav fixes plus dead reckoning, based on an em-log below the ship's hull.

The cruise track was validated against digital coastline data and generally shows good agreement, even where the ship passed into the higher reaches of estuaries.

In addition to the true position, tidally corrected navigation is also included. This is the position that the water sampled at a given instant would have been when logging commenced (i.e. the time of the first data cycle). The correction was determined using a numerical model and gives good results in the open sea but is less reliable near the coast where topography dominates the tidal displacement.

Bathymetry

The bathymetric depth was measured using a Simrad echo sounder with the transducer.

Project Information

North Sea Project

The North Sea Project (NSP) was the first Marine Sciences Community Research project of the Natural Environment Research Council (NERC). It evolved from a NERC review of shelf sea research, which identified the need for a concerted multidisciplinary study of circulation, transport and production.

The ultimate aim of the NERC North Sea Project was the development of a suite of prognostic water quality models to aid management of the North Sea. To progress towards water quality models, three intermediate objectives were pursued in parallel:

• Production of a 3-D transport model for any conservative passive constituent, incorporating improved representations of the necessary physics - hydrodynamics and dispersion;
• Identifying and quantifying non-conservative processes - sources and sinks determining the cycling and fate of individual constituents;
• Defining a complete seasonal cycle as a database for all the observational studies needed to formulate, drive and test models.

Proudman Oceanographic Laboratory hosted the project, which involved over 200 scientists and support staff from NERC and other Government funded laboratories, as well as seven universities and polytechnics.

The project ran from 1987 to 1992, with marine field data collection between April 1988 and October 1989. One shakedown (CH28) and fifteen survey cruises (Table 1), each lasting 12 days and following the same track, were repeated monthly. The track selected covered the summer-stratified waters of the north and the homogeneous waters in the Southern Bight in about equal lengths together with their separating frontal band from Flamborough head to Dogger Bank, the Friesian Islands and the German Bight. Mooring stations were maintained at six sites for the duration of the project.

Alternating with the survey cruises were process study cruises (Table 2), which investigated some particular aspect of the science of the North Sea. These included fronts (nearshore, circulation and mixing), sandwaves and sandbanks, plumes (Humber, Wash, Thames and Rhine), resuspension, air-sea exchange, primary productivity and blooms/chemistry.

In addition to the main data collection period, a series of cruises took place between October 1989 and October 1990 that followed up work done on previous cruises (Table 3). Process studies relating to blooms, plumes (Humber, Wash and Rhine), sandwaves and the flux of contaminants through the Dover Strait were carried out as well as two `survey' cruises.

The data collected during the observational phase of the North Sea Project comprised one of the most detailed sets of observations ever undertaken in any shallow shelf sea at that time.

Data Activity or Cruise Information

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: