Metadata Report for BODC Series Reference Number 1114344


Metadata Summary

Data Description

Data Category Platform orientation and velocity
Instrument Type
NameCategories
Gyrocompass  platform attitude sensors
Trimble 4000AX Global Positioning System receiver  NAVSTAR Global Positioning System receivers
Ashtech ADU2 Global Positioning System receiver  NAVSTAR Global Positioning System receivers
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Dr Stuart Cunningham
Originating Organization National Oceanography Centre, Southampton
Processing Status banked
Project(s) Rapid Climate Change Programme
RAPIDMOC
 

Data Identifiers

Originator's Identifier D304.QXF_NAV
BODC Series Reference 1114344
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2006-05-12 00:01
End Time (yyyy-mm-dd hh:mm) 2006-06-04 19:01
Nominal Cycle Interval 120.0 seconds
 

Spatial Co-ordinates

Southernmost Latitude 23.78100 N ( 23° 46.9' N )
Northernmost Latitude 28.46400 N ( 28° 27.8' N )
Westernmost Longitude 50.42750 W ( 50° 25.7' W )
Easternmost Longitude 13.35983 W ( 13° 21.6' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth -
Maximum Sensor Depth -
Minimum Sensor Height -
Maximum Sensor Height -
Sea Floor Depth -
Sensor Distribution -
Sensor Depth Datum -
Sea Floor Depth Datum -
 

Parameters

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)
ALATGP01 1 Degrees Lat_GPS Latitude north (WGS84) by unspecified GPS system
ALONGP01 1 Degrees Lon_GPS Longitude east (WGS84) by unspecified GPS system
APDAGP01 1 Degrees True CMG_GPS Direction of motion (over ground) of measurement platform {course made good} by unspecified GPS system
APEWGP01 1 Centimetres per second PlatformVelE_GPS Eastward velocity (over ground) of measurement platform by unspecified GPS system
APNSGP01 1 Centimetres per second PlatformVelN_GPS Northward velocity (over ground) of measurement platform by unspecified GPS system
APSAGP01 1 Metres per second GPS Speed (over ground) of measurement platform by unspecified GPS system
DSRNCV01 1 Kilometres Cmpval Distance travelled
HEADCM01 1 Degrees Platform_Heading Orientation (horizontal relative to true north) of measurement device {heading}
 

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

Ashtech Global Positioning System receivers (ADU series)

The ADU series of Global Positioning System (GPS) receivers are designed to give real-time three-dimensional position and attitude measurements. Attitude determination is based on differential carrier phase measurements between four antennas connected to a receiver, providing heading, pitch and roll, along with three-dimensional position and velocity.

The ADU2 model receives information from 48 channels, while the upgraded model (ADU5) uses 56 channels. The ADU5 also features a unique Kalman filter with user selectable dynamic modes to match operating conditions. It also incorporates signals from Satellite Based Augmentation Systems (SBAS) and features an embedded 2-channel 300 kHz beacon receiver for easy differential GPS (DGPS) operations.

Specifications

Parameter ADU2 ADU5

Operational Temperature range:
Antenna
Receiver


-40°C to 65°C
-20°C to 55°C


-40°C to 65°C
-20°C to 55°C

Sampling frequency 5 Hz 5 Hz
Receiver channels 48 56

Accuracy:
Heading
Pitch/Roll


0.2° rms (dynamic) - 0.4° rms (static)
0.4° rms (dynamic) - 0.8° rms (static)


0.02° to 0.2° rms
0.04° to 0.4° rms

Circular Error Probability:
Autonomous
Differential


5.0 m
1.0 m


3.0 m
0.4 to 1.0 m

Further details can be found in the manufacturer's specification sheets for the ADU2 and ADU5 .

RAPID Cruise D304 Navigation Instrumentation

Sensor Serial number Last calibration date
Trimble GPS4000 DS Surveyor - -
Ashtech ADU-2 multi antenna GPS with attitude - -
Ashtech GPS G12 integral to the Fugro Seastar DGPS receiver - -
Ashtech GG24+ GPS/Glonass receiver - -
Simrad EA500 Precision echosounder - -

RAPID Cruise D304 Navigation Data Processing

Data processing procedures

Originator's processing

Data were taken from the ship's TECHSAS streams and formatted into PSTAR netCDF format. All times were defined as seconds from 00:00:00 01/01/2006.

Data were removed that were not in the correct chronological order. Data from the Ashtech GPS is used to correct the heading given by the gyro compass. The differences are calculated and then cleaned to produce a correction. This is then applied to the heading from the gyro compass. Further information on originator's processing can be obtained in the D304 cruise report.

BODC processing

All 1 second navigational data were transferred from PSTAR format into BODC internal format (a netCDF subset) to allow use of the in-house visualisation tool (EDSERPLO). The following table shows the mapping of variables from the originator's files to standardised BODC parameters, along with unit conversions where applicable.

Parameter Originator Units BODC Parameter code Units Comments
Latitude ° (+ve N) ALATGP01 ° (+ve N) -
Longitude ° (+ve E) ALONGP01 ° (+ve E) -
Ship's direction of motion over ground ° true APDAGP01 ° true -
Eastward velocity over ground ms -1 APEWGP01 cms -1 Unit conversion: *100
Northward velocity over ground ms -1 APNSGP01 cms -1 Unit conversion: *100
Ship's speed over ground ms -1 APSAGP01 ms -1 -
Distance travelled km DSRNCV01 km Computed at BODC
Ship's heading ° HEADCM01 ° Orientation of vessel by Gyro-compass

Each data channel was visually inspected and any spikes or periods of dubious data flagged as suspect. The capabilities of the screening software allows comparative screening checks between channels.

Navigation was checked for gaps and improbable ship speeds at BODC. Improbable speeds were found where the latitude and longitude data had unrealistic values. Some improbable speeds occurred where the latitude and longitude had been constant for a while preceding the high speed. On inspection, it appeared that the GPS data were sticking at constant values and then suddenly jump back to being correct. The periods of constant latitude and longitude were flagged null and, along with any gaps, linearly interpolated over.

Distance run was recalculated using the clean latitude and longitude at BODC.

Bathymetric depth data were not supplied by the originator.

References

Rayner, D., et al 2007. RV Ronald H. Brown Cruise RB0602 and RRS Discovery Cruise D304, RAPID mooring cruise report March and May 2006. Southampton, UK, National Oceanography Centre, Southampton, 165pp. (National Oceanography Centre Southampton Cruise Report, 16)


Project Information

Rapid Climate Change (RAPID) Programme

Rapid Climate Change (RAPID) is a £20 million, six-year (2001-2007) programme of the Natural Environment Research Council (NERC). The programme aims to improve our ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.

Scientific Objectives

Projects

Overall 38 projects have been funded by the RAPID programme. These include 4 which focus on Monitoring the Meridional Overturning Circulation (MOC), and 5 international projects jointly funded by the Netherlands Organisation for Scientific Research, the Research Council of Norway and NERC.

The RAPID effort to design a system to continuously monitor the strength and structure of the North Atlantic Meridional Overturning Circulation is being matched by comparative funding from the US National Science Foundation (NSF) for collaborative projects reviewed jointly with the NERC proposals. Three projects were funded by NSF.

A proportion of RAPID funding as been made available for Small and Medium Sized Enterprises (SMEs) as part of NERC's Small Business Research Initiative (SBRI). The SBRI aims to stimulate innovation in the economy by encouraging more high-tech small firms to start up or to develop new research capacities. As a result 4 projects have been funded.


Monitoring the Meridional Overturning Circulation at 26.5N (RAPIDMOC)

Scientific Rationale

There is a northward transport of heat throughout the Atlantic, reaching a maximum of 1.3PW (25% of the global heat flux) around 24.5°N. The heat transport is a balance of the northward flux of a warm Gulf Stream, and a southward flux of cooler thermocline and cold North Atlantic Deep Water that is known as the meridional overturning circulation (MOC). As a consequence of the MOC northwest Europe enjoys a mild climate for its latitude: however abrupt rearrangement of the Atlantic Circulation has been shown in climate models and in palaeoclimate records to be responsible for a cooling of European climate of between 5-10°C. A principal objective of the RAPID programme is the development of a pre-operational prototype system that will continuously observe the strength and structure of the MOC. An initiative has been formed to fulfill this objective and consists of three interlinked projects:

The entire monitoring array system created by the three projects will be recovered and redeployed annually until 2008 under RAPID funding. From 2008 until 2014 the array will continue to be serviced annually under RAPID-WATCH funding.

The array will be focussed on three regions, the Eastern Boundary (EB), the Mid Atlantic Ridge (MAR) and the Western Boundary (WB). The geographical extent of these regions are as follows:

References

Baehr, J., Hirschi, J., Beismann, J.O. and Marotzke, J. (2004) Monitoring the meridional overturning circulation in the North Atlantic: A model-based array design study. Journal of Marine Research, Volume 62, No 3, pp 283-312.

Baringer, M.O'N. and Larsen, J.C. (2001) Sixteen years of Florida Current transport at 27N Geophysical Research Letters, Volume 28, No 16, pp3179-3182

Bryden, H.L., Johns, W.E. and Saunders, P.M. (2005) Deep Western Boundary Current East of Abaco: Mean structure and transport. Journal of Marine Research, Volume 63, No 1, pp 35-57.

Hirschi, J., Baehr, J., Marotzke J., Stark J., Cunningham S.A. and Beismann J.O. (2003) A monitoring design for the Atlantic meridional overturning circulation. Geophysical Research Letters, Volume 30, No 7, article number 1413 (DOI 10.1029/2002GL016776)


Data Activity or Cruise Information

Cruise

Cruise Name D304
Departure Date 2006-05-12
Arrival Date 2006-06-06
Principal Scientist(s)Torsten Kanzow (National Oceanography Centre, Southampton)
Ship RRS Discovery

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