Metadata Report for BODC Series Reference Number 1192041

Metadata Summary

Data Description

Data Category Bathymetry
Instrument Type
Kongsberg (Simrad) EM 120 multibeam echosounder  multi-beam echosounders
Trimble Applanix POSMV global positioning system  Differential Global Positioning System receivers; inertial navigation systems; Kinematic 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) RAPIDMOC

Data Identifiers

Originator's Identifier EASTERNBOUNDARY
BODC Series Reference 1192041

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2011-09-11 19:15
End Time (yyyy-mm-dd hh:mm) 2011-09-12 06:30
Nominal Cycle Interval -

Spatial Co-ordinates

Southernmost Latitude 27.74808 N ( 27° 44.9' N )
Northernmost Latitude 28.01182 N ( 28° 0.7' N )
Westernmost Longitude 13.76087 W ( 13° 45.7' W )
Easternmost Longitude 13.42910 W ( 13° 25.7' 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 -


BODC CODE Rank Units Short Title Title
ACYCAA01 1 Dimensionless Record_No Sequence number
ALATGP01 1 Degrees Lat_GPS Latitude north (WGS84) by unspecified GPS system
ALONGP01 1 Degrees Lon_GPS Longitude east (WGS84) by unspecified GPS system
MBANZZ01 1 Metres BathyDepES_ISL Sea-floor depth (below instantaneous sea level) {bathymetric depth} in the water body by echo sounder

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

Kongsberg EM120 Multibeam Echosounder

The EM120 is a low frequency (12 kHz) multibeam echosounder with full ocean depth capability designed for bathymetric surveys. It measures water depth by monitoring the travel time of an acoustic signal that is transmitted from the ship, reflected off the seabed and received back at the ship.

The main system units of the EM120 are transducer arrays (separate for reception and transmission), preamplifier unit, transceiver unit and operator unit. Sub-bottom profiling capability is an optional extra. For both transmit and receive arrays standard beamwidth is 1° or 2°, and 4° beamwidth is available for the receive array.

The system has 191 beams with pointing angles automatically adjusted according to achievable coverage or operator defined limits. The beam spacing is normally equidistant, corresponding to 1% of depth at 90° angular coverage, 2% at 120° and 3% at 140°. The transmit fan is split into several individual sectors, each of which is corrected independently for vessel roll, pitch and yaw, which places all soundings on a "best fit" to a line perpendicular to the survey line.

The EM120 supersedes the EM12 and was itself superseded by the EM122 in 2008.


Frequency 12 kHz
Maximum ping rate 5 Hz
Range sampling rate 2 kHz
Swath coverage sector up to 150°
Swath width up to 5.5 x water depth
Depth resolution 10 to 40 cm
Depth range 20 to 11,000 m
Pulse length 2, 5 and 15 ms
Number of beams 191
Beam width

1° x 1°
1° x 2°
2° x 2°
2° x 4°

Beam spacing (at angular coverage)

1% of depth at 90°
2% of depth at 120°
3% of depth at 140°

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

Trimble Applanix Position and Orientation Systems for Marine Vessels (POSMV)

The Position and Orientation Systems for Marine Vessels (POSMV) is a real time kinematic (RTK) and differential global positioning system (DGPS) receiver for marine navigation. It includes an inertial system that provides platform attitude information. The instrument provides accurate location, heading, velocity, attitude, heave, acceleration and angular rate measurements.

There are three models of Applanix POSMV, the POS MV 320, POS MV Elite and the POS MV WaveMaster. POS MV 320 and POS MV WaveMaster are designed for use with multibeam sonar systems, enabling adherence to IHO (International Hydrographic Survey) standards on sonar swath widths of greater than ± 75 degrees under all dynamic conditions. The POS MV Elite offers true heading accuracy without the need for dual GPS installation and has the highest degree of accuracy in motion measurement for marine applications.


POS MV 320
Componenet DGPS RTK GPS Outage
Position 0.5 - 2 m 1 0.02 - 0.10 m 1 <2.5 m for 30 seconds outages, <6 m for 60 seconds outages
Roll and Pitch 0.020° 0.010° 0.020°
True Heading 0.020° with 2 m baseline
0.010° with 4 m baseline
- Drift <1° per hour (negligible for outages <60 seconds)
Heave 5 cm or 5% 2 5 cm or 5% 2 5 cm or 5% 2
POS MV WaveMaster
Accuracy DGPS RTK GPS Outage
Position 0.5 - 2 m 1 0.02 - 0.10 m 1 <3 m for 30 seconds outages, <10 m for 60 seconds outages
Roll and Pitch 0.030° 0.020° 0.040°
True Heading 0.030° with 2 m baseline - Drift <2° per hour
Heave 5 cm or 5% 2 5 cm or 5% 2 5 cm or 5% 2
POS MV Elite
Accuracy DGPS RTK GPS Outage
Position 0.5 - 2 m 1 0.02 - 0.10 m 1 <1.5 m for 60 seconds outages DGPS, <0.5 m for 60 seconds outage RTK
Roll and Pitch 0.005° 0.005° 0.005°
True Heading 0.025° 0.025° Drift <0.1° per hour (negligible for outages <60 seconds)
Heave 3.5 cm or 3.5% 2 3.5 cm or 3.5% 2 3.5 cm or 3.5% 2

1 One Sigma, depending on quality of differential corrections
2 Whichever is greater, for periods of 20 seconds or less

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

JC064 Swath Bathymetry data processing

Originator's processing

RRS James Cook 's Kongsberg EM120 swath system (serial number 203) was used. A historical sound velocity profile derived from mooring data was used rather than gathering a currect sound velocity profile using the CTD or sound velocity profiler. Time limitations meant that no checks were made to the calibration of the swath bathymetry system before the surveys were carried out.

Eastern Boundary Glider site

The water depth was approximately 1000m. To maximise data coverage the beam width was set to ±70°, giving a swath width of 4000 to 5000m. The survey speed was initially 6 knots but increased to 8 then 9 knots on the last line to meet a time deadline. The sea conditions were calm. Additional data were incorporated from a line when the ship made passage to the area earlier in the day. No tidal corrections was applied to the data as it was suggested that tidal variations in this area are minimal, particularly when compared with the depth of the water.

Enough suitable data were collected to check the pitch and roll alignment of the EM120. For a pitch trench between lines 018 and 020, the Caris calibration module showed no pitch error. For the roll calibration, overlapping data between lines 024 and 026 were used. The Caris calibration module identified a roll error of +0.86°. However, when applied this estimate was deemed to great. A manual adjustment of the error to +0.30° gave the best fit. The data were manually cleaned using Caris' swath editor. Spikes in the data were marked as rejected, taking care to not remove real features. The depths were produced from an Uncertainty BASE surface. A geo-referenced TIFF image file was produced along with a gridded xy-depth text file, with depths at 25m intervals.


A dedicated survey at MAR0 was not performed and the data from the EM120 running continuously at the mooring site was used. As the vessel was either sat on station under DP control or steaming slowly during mooring operations there was a large number of overlapping data points. These were cleaned using swath and TPU order 2 filters, and some manual editing in the swath editor. A CUBE surface was used as its hypothesis as this was found to generate the most accurate surface from the overlapping data points. A geo-referenced TIFF image file was produced along with a gridded xy-depth text file.

BODC processing

The data were received in ASCII format in 2 files covering the MAR0 mooring site and the operational area of the SeaGlider Bellatrix within the Eastern Boundary Array of the RAPIDMOC mooring array.

Once the submitted data files are safely archived, the data undergo reformatting and banking procedures:

Parameter Mapping

The following describes the parameters contained in the originator's files and their mapping to BODC parameter codes.

Identifier Unit Definition BODC Parameter code Description Unit Unit conversion Comments
lat o Latitude north ALATGP01 Latitude north (WGS84) by unspecified GPS system o - Transferred
lon o Longitude west ALONGP01 Longitude east (WGS84) by unspecified GPS system o *-1 Transferred
depth m Depth MBANZZ01 Sea-floor depth (below instantaneous sea level){bathymetric depth} in the water column by echo sounder m - Transferred

Project Information

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:


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)

RAPID- Will the Atlantic Thermohaline Circulation Halt? (RAPID-WATCH)

RAPID-WATCH (2007-2014) is a continuation programme of the Natural Environment Research Council's (NERC) Rapid Climate Change (RAPID) programme. It aims to deliver a robust and scientifically credible assessment of the risk to the climate of UK and Europe arising from a rapid change in the Atlantic Meridional Overturning Circulation (MOC). The programme will also assess the need for a long-term observing system that could detect major MOC changes, narrow uncertainty in projections of future change, and possibly be the start of an 'early warning' prediction system.

The effort to design a system to continuously monitor the strength and structure of the North Atlantic MOC is being matched by comparative funding from the US National Science Foundation (NSF) for the existing collaborations started during RAPID for the observational arrays.

Scientific Objectives

This work will be carried out in collaboration with the Hadley Centre in the UK and through international partnerships.

Mooring Arrays

The RAPID-WATCH arrays are the existing 26°N MOC observing system array (RAPIDMOC) and the WAVE array that monitors the Deep Western Boundary Current. The data from these arrays will work towards meeting the first scientific objective.

The RAPIDMOC array consists of moorings focused in three geographical regions (sub-arrays) along 26.5° N: Eastern Boundary, Mid-Atlantic Ridge and Western Boundary. The Western Boundary sub-array has moorings managed by both the UK and US scientists. The other sub-arrays are solely led by the UK scientists. The lead PI is Dr Stuart Cunningham of the National Oceanography Centre, Southampton, UK.

The WAVE array consists of one line of moorings off Halifax, Nova Scotia. The line will be serviced in partnership with the Bedford Institute of Oceanography (BIO), Halifax, Canada. The lead PI is Dr Chris Hughes of the Proudman Oceanographic Laboratory, Liverpool, UK.

All arrays will be serviced (recovered and redeployed) either on an annual or biennial basis using Research Vessels from the UK, US and Canada.

Modelling Projects

The second scientific objective will be addressed through numerical modelling studies designed to answer four questions:

Data Activity or Cruise Information


Cruise Name JC064
Departure Date 2011-09-10
Arrival Date 2011-10-09
Principal Scientist(s)Stuart A Cunningham (National Oceanography Centre, Southampton)
Ship RRS James Cook

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