Metadata Report for BODC Series Reference Number 2026944
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
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Problem Reports
Bathymetry
The single-beam channel contains significantly more noise than the multi-beam channel. However, despite the abundance noisy signal fluctuations, the base line trend is identifiable and there is just one extended drop out period. However, over 50% of the cycles in this channel needed flagging due to the regularity of the noisy signal fluctuations. Consequently, this channel has not been retained.
RRS James Cook JC109 Navigation Quality Control Report
Position
Position channels look good. There were just are two gaps just at the start and end of the dataset, which were trimmed off at the end of processing.
Heading
Heading channel looks good. There are some large fluctuations within the permitted maximum and minimum parameter values and there are some parts of the datasets where absent values have been recorded. These absent values have been automatically flagged.
Bathymetry
A significant amount of noise was observed in the singlebeam channel whereas the multibeam channel has relatively low levels of noise but has multiple drop outs for extended periods. Despite this, all bathymetry channels show a similar pattern and follow GEBCO's trend with the exception of periods where dropouts have occurred.
The quality of the multibeam data is better than the singlebeam. There are some noisy periods, but the multibeam signal is of moderate quality overall. The base line signal is very distinct at times and approximately 40% of the multibeam channel has been flagged. This is primarily due to three extended drop out periods. Noisy signal fluctuations and drop outs have been flagged.
The single-beam channel contains a significant amount of noise. However, despite the abundance noisy signal fluctuations, the base line trend is identifiable and there is just one extended drop out period. However, over 50% of the cycles in this channel needed flagging due to the consistancy of noisy signal fluctuations. Noisy signal fluctuations and drop outs have been flagged.
The Multibeam channel is the preferred source of bathemetry.
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 EM122 12kHz Multibeam Echosounder
The EM122 is designed to perform seabed mapping to full ocean depth with a high resolution, coverage and accuracy. Beam focusing is applied both during reception and transmission. The system has up to 288 beams/432 soundings per swath with pointing angles, which are automatically adjusted according to achievable coverage or operator defined limits.
This model uses both Continuous Wave and Frequency Modulated sweep pulses with pulse compression on reception, in order to increase the maximum useful swath width. The transmit fan is split in several individual sectors, with independent active steering, in order to compensate for the vessel movements.
In multiplying mode, two swaths per ping cycle are generated, with up to 864 soundings. The beam spacing is equidistant or equiangular and the transmit fan is duplicated and transmitted with a small difference in along track tilt, which takes into account depth coverage and vessel speed, to give a constant sounding separation along track. In high density mode, more than one sounding per beam can be produced, such that horizontal resolution is increased and is almost constant over the whole swath.
The EM122 transducers are modular linear arrays in a Mills cross configuration with separate units for transmit and receive. If used to deliver sub-bottom profiling capabilities with a very narrow beamwidth, this system is known as SBP120 Sub-Bottom Profiler.
The specification sheet can be accessed here Kongsberg EM122.
Specifications
| Operational frequency | 12 Hz |
| Depth range | 20 to 11000 m |
| Swath width | 6 x depth, to approximately 30 km |
| Pulse forms | Continuous Wave and Frequency Modulated chirp |
| Swath profiles per ping | 1 or 2 |
| Sounding pattern | equidistant on bottom/equiangular |
| Depth resolution of soundings | 1 cm |
| Sidelobe suppression | -25 dB |
| Suppression of sounding artefacts | 9 frequency coded transmit sectors |
| Beam focusing | On transmit (per sector) and on reception (dynamic) |
| Swath width control | manual or automatic, all soundings intact even with reduced swath width |
| Motion compensation | |
| Yaw | ± 10° |
| Pitch | ± 10° |
| Roll | ± 15° |
EM122 versions
| System version | 0.5x1 | 1x1 | 1x2 | 2x2 | 2x4 | 4x4 |
| Transmit array (°) | 150x0.5 | 150x1 | 150x1 | 150x2 | 150x2 | 150x4 |
| Receive array (°) | 1x30 | 1x30 | 2x30 | 2x30 | 4x30 | 4x30 |
| No of beams/swath | 288 | 288 | 288 | 288 | 144 | 144 |
| Max no of soundings/swath | 432 | 432 | 432 | 432 | 216 | 216 |
| Max no of swaths/ping | 2 | 2 | 2 | 1 | 1 | 1 |
| Max no of soundings/ping | 864 | 864 | 864 | 432 | 216 | 216 |
RRS James Cook JC109 Navigation Instrumentation
Instrumentation
| Manufacturer | Model | Function | Comments |
| Trimble/Applanix GPS | POSMV | DGPS, Attitude & Ship Gyrocompasses | 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. |
| C- Nav | 3050 | DGPS and DGNSS | C&C Technologies C-Nav3050 satellite positioning system receiver |
| Kongsberg Seatex Seapath | Seapath 330 | DGPS | Sensor-based inertial navigation and Differential Global Positioning System (DGPS) receiver unit, providing heading, attitude and position. |
| Kongsberg Seatex DPS | DPS 116 | DPS | 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). |
| Sperry Marine Gyro | -Not Specified- | Gyrocompass | |
| Kongsberg Maritime | EA600 | Single Beam Echo Sounder | It comprises a standard EA600 single beam echosounder fitted with an additional 10 kHz transducer. The standard EA600 operates up to four high power transceivers simultaneously. Available EA600 standard frequencies span from 12 to 710 kHz with a variable power output of up to 2 kW and a 160 dB dynamic range. |
| Kongsberg Maritime | EM120 | Multibeam Echo Sounder | A multibeam 12 kHz echsounder designed for high resolution seabed mapping. It uses both Continuous Wave (CW) and Frequency Modulated (FM) sweep pulses with pulse compression on reception in order to increase the maximum used swath width. |
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.
Specifications
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.
RRS James Cook JC109 Navigation Data Processing Procedures
Originator's Data Processing
The data were logged by the TECHSAS (TECHnical and Scientific sensors Acquisition System) system into daily NetCDF files. The TECHSAS system is used as the main data logging system on NMF-SS operated reserach vessels. The daily TECHSAS NetCDF navigation and bathymetry files provided to BODC were used for BODC processing. Data were additionally logged into the RVS Level-C format files which have been archived at BODC.
Files delivered to BODC
| Filename | Content description | Format | Interval | Start date/time (UTC) | End date/time (UTC) | Comments |
| yyyymmdd-000000-position-Applanix_GPS_JC1.gps | Position of the ship Lat and Lon From Applanix POS MV | NetCDF | 1 sec. | 14-Oct-2014 17:37:00 | 05-Nov-2014 21:17:00 | |
| yyyymmdd-000000-gyro-GYRO1_JC1.gyr | Heading from POS MV gyro | NetCDF | 1 sec. | 14-Oct-2014 17:37:00 | 05-Nov-2014 21:17:00 | |
| yyyymmdd-000000-sb_depth-EM120_JC1.depth | Seafloor depth from EM120 multi beam | NetCDF | 4 sec | 15-Oct-2014 10:18:01 | 05-Nov-2014 15:24:43 | First two NETCDF files do not contain any data. |
| yyyymmdd-000000-EA600-EA600_JC1.EA600 | Seafloor depth from EA600 single beam | NetCDF | ~8-10 sec variation | 15-Oct-2014 06:59:41 | 05-Nov-2014 20:55:11 | First NETCDF file does not contain any data. |
BODC Data Processing
Data were banked at BODC following standard banking procedures. Data were averaged to 60 second intervals.
The originator's variables were mapped to appropriate BODC parameter codes as follows:
yyyymmdd-000000-position-Applanix_GPS_JC1.gps
| Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
| lat | decimal degrees | Latitude north | ALATGP01 | decimal degrees | none | |
| lon | decimal degrees | Longitude east | ALONGP01 | decimal degrees | none | |
| time | days since 1899-12-30 00:00:00 UTC | Acquisition time | Not transferred | |||
| Mode | N/A | Mode | Not transferred | |||
| Heading | degrees | True heading | Not transferred. | |||
| prec | dimensionless | Precision | Not transferred | |||
| alt | meters | Altitude | Not transferred. | |||
| gndcourse | Degrees | Ground course | Not transferred. | |||
| gndspeed | knot | Ground speed | Not transferred. | |||
| measureTS | day since 1899-12-30T00:00:00 UTC | Measure timestamp | Not transferred |
yyyymmdd-000000-gyro-GYRO1_JC1.gyr
| Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
| heading | Degrees true | True heading | HEADCM01 | degrees | none | |
| time | days since 1899-12-30 00:00:00 UTC | acquisition time | Not transferred. |
yyyymmdd-000000-sb_depth-EM120_JC1.depth
| Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
| snd | meters | Sounding | MBANSWCB | meters | none | Multibeam |
| freq | kHz | Frequency | Not transferred | |||
| time | days since 1899-12-30 00:00:00 UTC | acquisition time | Not transferred |
yyyymmdd-000000-EA600-EA600_JC1.EA600
| Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
| depthm | meters | Depth in meters | MBANZZ01 | meters | none | Single beam |
| DepthF | fathom | Depth in fathoms | Not transferred | |||
| depthft | feet | Depth in feet | Not transferred | |||
| time | days since 1899-12-30 00:00:00 UTC | acquisition time | Not transferred |
All the reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag.
Position
A check was run on positional data to identify gaps and improbable values (through the calculation of speed). There were drop outs in the positional data at the start and end of the file. These were flagged and trimmed after processing was complete.
Ship Velocities
Ship velocities were calculated from the main latitude and longitude channels using standard BODC procedures.
GEBCO
GEBCO bathymetry was added to the file using the main latitude and longitude channels.
Distance Run
Distance run was calculated from the main latitude and longitude channels, starting from the beginning of the file, using BODC standard procedures.
Bathymetry
Bathymetry data were screened independently as well as against GEBCO bathymetry measurements. Both the EA600 single-beam echo-sounder and EM120 multibeam echo-sounder follow GEBCO's trend. Unrealistic noisy values and absent data were flagged using BODC in-house EDSERPLO software. The EM120 multibeam echo-sounder dataset is a quality source of bathymetry.
Calibration
No field calibrations have been applied.
Project Information
Role and extent of detachment faulting at slow-spreading mid-ocean ridges
This is a 6 year project that aims to determine (1) the sub-surface geometry and extent of the detachments beneath the ridge axis, (2) the amount and detailed distribution of magmatic crust, and (3) the asymmetry of spreading rates associated with oceanic core complexes and the volcanic seafloor.
The research aims to make an improvement in our overall understanding of the nature and geometry of ocean detachments.
This project was funded by Natural Environment Research Council parent and child grants NE/J022551/1, NE/J02029X/1, and NE/J021741/1 led by Professor Tim Reston at the University of Birmingham, Professor Christine Pierce at Durham University, and Professor Chris MacLeod at Cardiff Univserity respectively. The project is funded from April 2013 to August 2020.
Data Activity or Cruise Information
Cruise
| Cruise Name | JC109 |
| Departure Date | 2014-10-11 |
| Arrival Date | 2014-11-05 |
| Principal Scientist(s) | Christine Peirce (University of Durham, Department of Earth Sciences) |
| 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 |
| B | nominal value |
| Q | value below limit of quantification |
