Planned maintenance — 18th January 2018 12:00 to 22nd January 2018 09:00 [more]

Metadata Report for BODC Series Reference Number 1359758

Metadata Summary

Data Description

Data Category Bathymetry
Instrument Type
Kongsberg (Simrad) EM 120 multibeam echosounder  multi-beam echosounders
Ashtech GG24 Global Positioning System and Global Navigation Satellite System receiver  Global Navigation Satellite System receivers; NAVSTAR Global Positioning System receivers
Trimble 4000DS Global Positioning System receiver  Differential Global Positioning System receivers
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Prof Tim Jickells
Originating Organization University of East Anglia School of Environmental Sciences
Processing Status banked
Project(s) Atlantic Meridional Transect Phase2(AMT)

Data Identifiers

Originator's Identifier AMT12_PRODQXF_NAV
BODC Series Reference 1359758

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2003-05-13 12:24
End Time (yyyy-mm-dd hh:mm) 2003-06-15 10:54
Nominal Cycle Interval 60.0 seconds

Spatial Co-ordinates

Southernmost Latitude 50.31773 S ( 50° 19.1' S )
Northernmost Latitude 49.42640 N ( 49° 25.6' N )
Westernmost Longitude 53.68221 W ( 53° 40.9' W )
Easternmost Longitude 4.82058 W ( 4° 49.2' 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
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)
ALATTR01 1 Degrees Lat_TrimbleGPS Latitude north (WGS84) by Trimble GPS
ALONTR01 1 Degrees Lon_TrimbleGPS Longitude east (WGS84) by Trimble GPS
APEWTR01 1 Centimetres per second PlatformVelE_GPS Eastward velocity (over ground) of measurement platform by Trimble GPS
APNSTR01 1 Centimetres per second PlatformVelN_GPS Northward velocity (over ground) of measurement platform by Trimble GPS
HEADCM01 1 Degrees Platform_Heading Orientation (horizontal relative to true north) of measurement device {heading}
MBANUA01 1 Metres BathyDepES_1500 Sea-floor depth (below instantaneous sea level) {bathymetric depth} in the water body by echo sounder (SV=1500m/s)

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

RRS James Clark Ross Cruise AMT12 (JR20030512) - Underway Navigation and Bathymetry Data Quality Report

Bathymetry has only had rudimentary flagging applied and care should be taken using these data.

Further to this there are no additional known data quality issues.

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 .

Ashtech GG24 receiver

The GG24 is an all-in-view Global Positioning System (GPS) and Global Navigation Satellite System (GLONASS) receiver that blends GPS and GLONASS into a single position solution. This receiver uses all available satellites from both systems to obtain the best position information.

The three-dimensional position and velocity are calculated when tracking any combination of five satellites. Up to five independent measurements are determined every second, with no interpolation or extrapolation from previous solutions.


Parameter Values
Operating Temperature -30°C to 55°C
Sampling frequency up to 5 Hz
Receiver channels 12 L1 GPS + 12 L1 GLONASS
Real-Time Position Accuracy

3.2 m (autonomous)

35.0 m (differential)

Velocity Accuracy 0.1 knots

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

RRS James Clark Ross Cruise AMT12 (JR20030512) - Underway Navigation and Bathymetry Instrumentation Document

The following instruments were used for the navigation and bathymetry measurements:


Manufacturer Model Main Function Serial Number Comments
Trimble 4000DS Position (Latitude and Longitude) - -
Ashtec (GLONASS) GG24 GPS Heading - -
Simrad Kongsberg EM120 Bathymetry - -

Trimble 4000DS Global Positioning System receiver

The Trimble 4000DS Differential Surveyor is similar to the 4000RS (a Maxwell-based receiver that is oriented toward precision positioning applications. It is intended for use as a DGPS base station, generating RTCM-104 corrections). The 4000Ds can apply RTCM-104 corrections to the satellite data it receives in order to generate accurate position fixes in real time.

RRS James Clark Ross Cruise AMT12 (JR20030512) - Underway Navigation and Bathymetry Processing Document

Originator's Data Processing

The raw data were logged every second to the SCS logging system. The transferred latitude and longitude navigation data originated from the Trimble 4000DS Trimble Surveyor system using Marine Star differential corrections. Bathymetry was measured using a Kongsberg (Simrad) EM-120 multi-beam swath bathymetry echo sounder.

The data were submitted to BODC in ASCII output from the BAS SCS system for post-cruise processing and data banking.

BODC Data Processing


Data from the full-resolution SCS files were transferred to BODC's NetCDF format QXF under the BODC Underway Data System (BUDS). The transfer involved reducing the data to 60 second intervals.


Each data channel was inspected on a graphics workstation and any spikes or periods of dubious data were flagged. The power of the workstation software was used to carry out comparative screening checks between channels by overlaying data channels. A map of the cruise track was simultaneously displayed in order to take account of the oceanographic context.

Data processing, correction and calibration

Navigational data were available from three different systems on the JCR. These were screened in order to select the best quality data for the primary navigation channels. The data from the Trimble GPS system were consistently good and showed no spikes.

A program was run which located any null values in the latitude and longitude channels and checked to ensure that the ship's speed did not exceed 15 knots. No errors were found.

The ship's north and east velocity channels were derived using the Trimble GPS latitude and longitude channels, using the BODC Matlab function 'Velcal'.

Project Information

The Atlantic Meridional Transect - Phase 2 (2002-2006)

Who was involved in the project?

The Atlantic Meridional Transect Phase 2 was designed by and implemented by a number of UK research centres and universities. The programme was hosted by Plymouth Marine Laboratory in collaboration with the National Oceanography Centre, Southampton. The universities involved were:

What was the project about?

AMT began in 1995, with scientific aims to assess mesoscale to basin scale phytoplankton processes, the functional interpretation of bio-optical signatures and the seasonal, regional and latitudinal variations in mesozooplankton dynamics. In 2002, when the programme restarted, the scientific aims were broadened to address a suite of cross-disciplinary questions concerning ocean plankton ecology and biogeochemistry and the links to atmospheric processes.

The objectives included the determination of:

The data were collected with the aim of being distributed for use in the development of models to describe the interactions between the global climate system and ocean biogeochemistry.

When was the project active?

The second phase of funding allowed the project to continue for the period 2002 to 2006 and consisted of six research cruises. The first phase of the AMT programme ran from 1995 to 2000.

Brief summary of the project fieldwork/data

The fieldwork on the first three cruises was carried out along transects from the UK to the Falkland Islands in September and from the Falkland Islands to the UK in April. The last three cruises followed a cruise track between the UK and South Africa, only deviating from the traditional transect in the southern hemisphere. During this phase the research cruises sampled further into the centre of the North and South Atlantic Ocean and also along the north-west coast of Africa where upwelled nutrient rich water is known to provide a significant source of climatically important gases.

Who funded the project?

Natural Environment Research Council (NERC)

Data Activity or Cruise Information


Cruise Name JR20030512 (AMT12, JR102, JR88, JR90)
Departure Date 2003-05-12
Arrival Date 2003-06-17
Principal Scientist(s)Tim Jickells (University of East Anglia School of Environmental Sciences)
Ship RRS James Clark Ross

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