Metadata Report for BODC Series Reference Number 1801894
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
No Problem Report Found in the Database
RRS James Cook cruise JC150 navigation quality control report
Bathymetry
The channel has been flagged throughout the cruise where noise in the channel moves away from the baseline bathymetry. Drop outs of zero values were converted to the absent data value. (BODC assessment)
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The EM120 supersedes the EM12 and was itself superseded by the EM122 in 2008.
Specifications
| 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° |
| Beam spacing (at angular coverage) | 1% of depth at 90° |
Further details can be found in the manufacturer's specification sheet.
RRS James Cook cruise JC150 navigation instrumentation
Instrumentation
| Manufacturer | Model | Function | Comments |
| Trimble/Applanix | POSMV | DGPS and attitude | Primary source of position. |
| Kongsberg Maritime | Simrad EA600 | Single-beam echo sounder (port drop keel) | Not corrected for sound velocity. |
| Kongsberg Maritime | Simrad EM120 | Multi-beam echo sounder (shallow) | Corrected for sound velocity. |
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 cruise JC150 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-POSMV_GPS.gps | Position (latitude and longitude) (from POSMV) | NetCDF | ~ 1 sec. | 22/06/2017 12:11:25 | 12/08/2017 07:51:23 | - |
| yyyymmdd-000000-gyro-POSMV_GYRO.gyr | True heading (from POSMV Gyro) | NetCDF | ~ 1 sec. | 22/06/2017 12:11:25 | 12/08/2017 07:51:23 | Most accurate source of heading from the ship's gyros |
| yyyymmdd-000000-EA600-EA600_DEPTH.EA600 | Depths from central beam EA600 single-beam echosounder | NetCDF | ~15 seconds | 29/06/2017 12:16:13 | 09/08/2017 12:44:01 | |
| yyyymmdd-000000-sb_depth-EM120_DEPTH.depth | Depths from the EM120 multi-beam echosounder | NetCDF | ~20 seconds | 29/06/2017 12:16:46 | 08/08/2017 16:29:53 |
|
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-POSMV_GPS.gps
| Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
| measureTS | day since 1899-12-30T00:00:00 UTC | Measure timestamp | Not transferred | |||
| gndspeed | knot | Ground speed | Not transferred. | |||
| gndcourse | Degrees | Ground course | Not transferred. | |||
| alt | meters | Altitude | Not transferred. | |||
| lat | decimal degrees | Latitude north | ALATGP01 | decimal degrees | none | |
| prec | dimensionless | Precision | Not transferred | |||
| lon | decimal degrees | Longitude east | ALONGP01 | decimal degrees | none | |
| Heading | degrees | True heading | Not transferred | |||
| Mode | dimensionless | GPS mode | Not transferred | |||
| time | days since 1899-12-30 00:00:00 UTC | Acquisition time | Not transferred |
yyyymmdd-000000-gyro-POSMV_GYRO.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_DEPTH.depth
| Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
| freq | kHz | Frequency | Not transferred | |||
| snd | meters | sounding | MBANSWCB | meters | none | Multi-beam - Best quality bathymetry channel |
| time | days since 1899-12-30 00:00:00 UTC | acquisition time | Not transferred |
yyyymmdd-000000-EA600-EA600_DEPTH.EA600
| Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
| DepthF | fathom | Depth in fathoms | Not transferred | |||
| depthm | meters | Depth in meters | MBANZZ01 | meters | none | Single beam |
| 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 gaps in the positional data and these gaps were present due to crashes in the Techsas data acquisition system. During BODC processing, these gaps were linearly interpolated to remove them.
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. Bathymetry data from the EM120 multi -beam echo-sounder were deemed to be the best quality. The EM120 multi-beam is run with a sound velocity correction. The EA600 single-beam is run without a sound velocity correction.
Calibration
No field calibrations have been applied.
Project Information
Zinc, iron and phosphorous co-limitation in the Ocean: ZIPLOc
ZIPLOc is an 3 year project that aims to measure how zinc and phosphorous control biological activity in the North Atlantic subtropical gyre using novel measurement techniques. The observations made will be further explored using the latest modelling techniques over decadal timescales and in other basins.
The research aims to make an improvement in our overall understanding of how subtropical gyre ecosystems respond to ongoing climate change.
The project is led by the University of Liverpool, Earth, Ocean and Ecological Sciences and is a collaboration with the University of Southampton, School of Ocean and Earth Science. The project received funding from the Natural Environmental Research Council and runs between January 2017 and February 2020.
Data Activity or Cruise Information
Cruise
| Cruise Name | JC150 (GApr08, ZIPLOC) |
| Departure Date | 2017-06-25 |
| Arrival Date | 2017-08-12 |
| Principal Scientist(s) | Claire Mahaffey (University of Liverpool Department of Earth, Ocean and Ecological 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 |
