Metadata Report for BODC Series Reference Number 1762193

Metadata Summary

Data Description

Data Category Bathymetry
Instrument Type
Simrad EA500 echosounder  single-beam echosounders
Ashtech ADU5 Global Positioning System receiver  Differential Global Positioning System receivers
Kongsberg Seatex Seapath 200 Global Positioning System receiver and Gyrocompass  platform attitude sensors; Differential Global Positioning System receivers
Trimble Applanix POSMV global positioning system  Differential Global Positioning System receivers; inertial navigation systems; Kinematic Global Positioning System receivers
Kongsberg Seatex Differential Positioning Sensor 116  Differential Global Positioning System receivers
Sperry Marine NAVIGAT X MK 1 digital gyrocompass  platform attitude sensors
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Mr John Seddon
Originating Organization National Marine Facilities Sea Systems
Processing Status banked
Project(s) Oceans 2025 Theme 10 SO1:AMT

Data Identifiers

Originator's Identifier JC053_PRODQXF_NAV
BODC Series Reference 1762193

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2010-10-12 10:40
End Time (yyyy-mm-dd hh:mm) 2010-11-22 21:10
Nominal Cycle Interval 60.0 seconds

Spatial Co-ordinates

Southernmost Latitude 48.10750 S ( 48° 6.4' S )
Northernmost Latitude 50.75433 N ( 50° 45.3' N )
Westernmost Longitude 56.12467 W ( 56° 7.5' W )
Easternmost Longitude 1.36100 W ( 1° 21.7' 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
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
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
DSRNCV01 1 Kilometres Cmpval Distance travelled
HEADCM01 1 Degrees Platform_Heading Orientation (horizontal relative to true north) of measurement device {heading}
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

AMT RRS James Cook Cruise JC053 AMT20 Navigation and Bathymetry Data Quality Document

The navigation data have been through BODC quality control screening. The gaps of less than ten minutes have been filled by interpolation. Overall the navigation data for the cruise duration appear good.

The bathymetry channel has been flagged to remove the most obvious suspect data but for many periods the variation was large and frequent. The data became visibly noisier after 6th November 2010.

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.


Operational range 1, 5, 10, 15, 25, 50, 100, 150, 250, 500, 750, 1000, 2500, 5000 and 10000 m
Phasing 0 to 10000 m in 1 m increments (manual or automatic)
Non saturated instantaneous input range -160 to 0 dB
Output power regulation 0 to 20 dB relative to full power
Noise figure 10 dB
Operating temperature 0 to 55°C
Ping rate max 10 pings per second (adjustable)

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

AMT RRS James Cook Cruise JC053 AMT20 Navigation and Bathymetry Instrument Description Document

Instrument Type
Ashtech ADU5 GPS based attitude measuring system GPS
Seapath 200 GPS unit GPS
Applanix POSMV GPS unit GPS
DPS116 GPS unit GPS
Ship's Gyrocompass Gyro compass
Simrad EA500 Precision Echo Sounder Echosounder

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.


Parameter ADU2 ADU5

Operational Temperature range:

-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


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:

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 .

Kongsberg Seatex Differential Positioning Sensor 116

A 14-channel, all-in-view, L1 GPS receiver which primarily utilises the free, WAAS, EGNOS and MSAS Satellite Based Augmentation Systems (SBAS) for differential corrections (DGPS). It is also capable of simultaneous DGPS from a wide variety of other reference stations (Multiref), resulting in improved accuracy. Simultaneous reception and use of correction signals in MF and UHF frequency bands, Inmarsat standard A, B and M terminals and SeaSTAR Spot, are possible.

DGPS position accuracy with SBAS service < 1.5 m, 95% CEP (*)
0.6 m, 1θ (*)
DGPS position accuracy (Multiref) < 1 m, 95% CEP (**)
0.4 m, 1θ (**)
Velocity accuracy 0.05 m/s, 95% CEP (**)
0.02 m/s, 1θ (**)
Output rate 1 Hz

(*) Accuracy specifications are based on real-life tests conducted using WAAS and an open view to the sky in Houston, Texas.

(**) Accuracy specifications are based on real-life tests conducted under low multipath conditions and an open view to the sky in Trondheim, Norway. Tests at different locations under different conditions may produce different results.

Full specifications can be found here .

Kongsberg Seatex Seapath 200 GPS and Gyrocompass

The Seapath 200 is a highly accurate, real-time heading, attitude and position information system that integrates the best signal characteristics of Inertial Measurement Units (IMU) and Global Positioning System (GPS), using a differential GPS method to acquire this data.

The high-rate motion data is obtained from the Seatex MRU5 inertial sensor and two fixed baseline GPS carrier-phase receivers. The raw data is integrated in a Kalman filter in the Seapath Processing Unit. The IMU contains an accurate linear accelerometer and Bosch Coriolis force angular rate gyros (CFG).

This system is equipped to utilise up to six different DGPS reference stations, it checks for consistency within measurements from the different sensors to ensure reliability and rejects noisy data or reports its inaccuracy. The data is available through various output protocols, RS-232, RS-422 and Ethernet.

This instrument is no longer in production; the main characteristics are presented below, and the specification sheet can be accessed here Kongsberg Seatex Seapath 200 .


Scale factor error in pitch, roll and heading 0.2% RMS
Heave motion periods 1 to 25 s

0.05° RMS (4 m baseline)

0.075° RMS (2.5 m baseline)

Roll and Pitch 0.03° EMS (± 5° amplitude)
Heave 5 cm or 5%, whichever is highest

0.7 RMS or 1.5 m (95% CEP) with DGPS

0.15 m EMS or 0.4 m (95% CEP) with Searef 100 corrections

Velocity 0.03 m s -1 RMS or 0.07 m s -1 (95% CEP) with DGPS

Sperry Marine NAVIGAT X MK 1 digital gyrocompass

A digital gyrocompass for use in marine navigation. The system comprises a gyrosphere supported in fluid, suspended at a single point. The centering pin retaining arrangement can be mounted in an additional gimbal system for high speed applications (Mod 7). The system can drive up to 12 analogue repeaters and has 7 independent serial outputs and 2 dependent 6 steps/° heading outputs. The NAVIGAT X MK1 was the first of the Sperry Marine range of heading sensors, which comprises the NAVIGAT 3000 fibreoptic gyrocompass, the NAVIGAT X MK 1 and the NAVIGAT X MK 2 digital gyrocompasses.


Heading accuracy <0.1° secant latitude (linear mean settle point error)
<0.1° secant latitude (static)
<0.4° secant latitude (dynamic)
Freedom of pitch and roll ±40° (Mod 10)
±90° (Mod 7)

Detailed specifications can be found in the manufacturer's data 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.

AMT RRS James Cook Cruise JC053 AMT20 Navigation and Bathymetry Processing Procedures Document

Originator's Data Processing

Navigation and bathymetry (HPPLAT)

During the cruise there was a dual logging system in place on the RRS James Cook. Data from the various instruments were logged to the RVS Level-C system and also as NetCDF (binary) through the Ifremer Techsas data logging system. In addition to the GPS systems the following instruments were logged during the cruise:

1) Chernikeef EM speed log (logged to RVS format as log_chf)
2) Ships Gyrocompass (logged to RVS format as gyro)
3) Simrad EA600 Precision Echo Sounder (logged to RVS format as ea600m)

Processing was carried out using the RVS software suite. The following routines were run on the navigation and bathymetry data channels to produce files named after the routine that generated them:
RELMOV - Relmov is the relative motion file for this cruise. This was generated using the ships gyro and ships Chernikeef Log data to extract a movement in a given direction. This was then used by bestnav when and where necessary to calculate fixes if GPS fixes were not available.
BESTNAV - Bestnav uses all 3 GPS Systems logged and creates a best suite stream by providing an as complete account of the ships track as possible. This is done by reading all 3 GPS streams with gps_g2 being primary, gps_4000 as secondary and gps_ash as tertiary. The system looks for gaps of a certain length in the primary and when it finds those gaps it requests that the next gps down fill in the gaps. If no GPS data is available it asks RELMOV to fill in until data is available again. Then the system calculates back over itself to ensure that the extrapolated positions are correct using the GPS data available around the gap.
BESTDRF - Bestdrf is a product of bestnav. When run bestnav uses the relmov data which contains a predicted vn and ve based upon direction and speed through the water. The Bestdrf file is the accurate drift velocity of what actually occurred based on the GPS changes between each record.

Filename Data type Start Calendar Day Start Time Finish Calendar Day Finish Time Data Interval
bestnav RVS Level-C processed 2010-10-12 10:40:50 2010-11-22 21:10:00 10 seconds
ea600m RVS Level-C raw 2010-10-12 19:02:09 2010-11-22 21:10:09 1 second

BODC Data Processing

Navigation and bathymetry from processed RVS format files, along with meteorological and underway seawater data from the raw RVS files were transferred to BODC's NetCDF format (QXF) under the BODC Underway Data System (BUDS). This transfer involved reducing the data by averaging to 60 second intervals. Directional data were reduced by averaging using a unit circle.

Navigation and bathymetry (HPPLAT)

The bestnav data were transferred as used as the source for cruise navigation data. A description of the channels present in the files, units, whether they were transferred, BODC parameter code and units, and if a unit conversion was applied during the transfer are detailed in the table below:

bestnav Channels Description Units BODC Parameter Code Units Conversion Factor
lat Latitude Degrees +ve N ALATGP01 Degrees +ve N *1
lon Longitude Degrees +ve E ALONGP01 Degrees +ve E *1
vn northwards velocity knots APNSGP01 cm s -1 *51.44
ve eastwards velocity knots APEWGP01 cm s -1 *51.44
mode mode that the GPS was operating in. 0 indicates an invalid fix, 1 a GPS fix and 2 a DGPS fix - not for transfer - -
cmg Course made good Degrees True APDAGP01 Degrees True *1
smg Speed made good knots APSAGP01 m s -1 *0.514
dist_run Distance run Nautical miles DSRNCV01 km *1.852
Heading Ship's heading Degrees true HEADCM01 Degrees true *1
ea600m Channels Description Units BODC Parameter Code Units Conversion Factor
depth Bathymetric depth m MBANZZ01 m *1

Once the data in the RVS navigation file 'bestnav' were transferred to the BODC QXF format, a Matlab program ('navcheck') 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. There were a few small gaps (<5 minutes) in the latitude and longitude channels, these were filled using the Matlab program 'navint' to interpolate data to fill the gaps. In addition the 'navcheck' routine checked the vessel's speed over the ground from the navigation data for values that are outside an expected range. There were no warnings indicated. The latitude and longitude channels were screened by plotting the course on to a map of the Atlantic Ocean. There was no further flagging required.


No calibrations were applied to the navigation or bathymetry channels by BODC.


Each data channel was inspected on a graphics workstation using BODC screening software EDSERPLO and any spikes or periods of dubious data were flagged using BODC quality control flag system. Impossible values were checked carefully and flagged null only if believed to be genuine missing or bad data. EDSERPLO 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.

Project Information

Oceans 2025 Theme 10, Sustained Observation Activity 1: The Atlantic Meridional Transect (AMT)

The Atlantic Meridional Transect has been operational since 1995 and through the Oceans 2025 programme secures funding for a further five cruises during the period 2007-2012. The AMT programme began in 1995 utilising the passage of the RRS James Clark Ross between the UK and the Falkland Islands southwards in September and northwards in April each year. Prior to Oceans 2025 the AMT programme has completed 18 cruises following this transect in the Atlantic Ocean. This sustained observing system aims to provide basin-scale understanding of the distribution of planktonic communities, their nutrient turnover and biogenic export in the context of hydrographic and biogeochemical provinces of the North and South Atlantic Oceans.

The Atlantic Meridional Transect Programme is an open ocean in situ observing system that will:

The specific objectives are:

The measurements taken and experiments carried out on the AMT cruises will be closely linked to Themes 2 and 5. The planned cruise track also allows for the AMT data to be used in providing spatial context to the Sustained Observation Activities at the Porcupine Abyssal Plain Ocean Observatory (SO2) and the Western Channel Observatory (SO10).

More detailed information on this Work Package is available at pages 6 - 9 of the official Oceans 2025 Theme 10 document: Oceans 2025 Theme 10


Data Activity or Cruise Information


Cruise Name JC053 (AMT20)
Departure Date 2010-10-12
Arrival Date 2010-11-25
Principal Scientist(s)Andrew Rees (Plymouth Marine Laboratory)
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