Metadata Report for BODC Series Reference Number 2053966
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
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 |
DY116 Underway Navigation Instrumentation
Instrumentation
The following scientific navigational and bathymetric systems were fitted.
| Manufacturer | Model | Function | Comments |
| Trimble/Applanix | POSMV | DGPS and attitude | Primary source of position for science. |
| Kongsberg Maritime | Simrad EA 640 | Singlebeam echo sounder | - |
| Kongsberg Maritime | Simrad EM 122 | Multibeam echo sounder | Best quality bathymetry source. |
| Sperry Marine | MK37 series gyrocompasses | GPS (ships heading) | - |
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.
DY116 Underway Navigation Data Processing Procedures
Originator's Data Processing
The data were logged by the TECHSAS (TECHnical and Scientific sensors Acquisition System) version 5.11 data logging system which is the main data logging system on NMF-SS operated research vessels. Data were processed daily using the National Oceanography Centre data processing routines into NetCDF files, and these TECHSAS (NetCDF) navigation and bathymetry files provided to BODC were used for BODC processing. Please refer to the DY116 cruise report for more information.
Files delivered to BODC
| Filename | Content description | Format | Interval | Start date/time (UTC) | End date/time (UTC) | Comments |
| *-*-position-POSMV_GPS.gps | Position, heading, speed over ground & coarse over ground | NetCDF | 1 sec | 09-Nov-2020 16:07:13 | 26-Nov-2020 14:32:07 | - |
| *-*-gyro-POSMV_GYRO.gyr | Heading | NetCDF | 1 sec | 09-Nov-2020 16:07:13 | 26-Nov-2020 14:32:08 | - |
| *-*-EA600-EA640_DEPTH.EA600 | bathymetry data from EA640 Singlebeam | NetCDF | 16 sec | 11-Nov-2020 08:28:47 | 25-Nov-2020 12:59:51 | - |
| *-*-sb_depth-EM120_DEPTH.depth | bathymetry data from EM122 Multibeam | NetCDF | 1 sec | 11-Nov-2020 10:24:50 | 23-Nov-2020 10:41:10 | - |
BODC Data Processing
The data were reformatted to the BODC internal format using standard banking procedures, and averaged at 60 second intervals. The following table shows how variables within the files were mapped to appropriate BODC parameter codes:
*-*-position-POSMV_GPS.gps
| Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
| lat | degrees | Latitude North | ALATGP01 | degrees | N/A | - |
| long | degrees | Longitude East | ALONGP01 | degrees | N/A | - |
| gndspeed | m/s | Speed over ground | APSAGP01 | m/s | * 0.5144444 | Knots to m/s |
| gndcourse | degrees | Course over ground | APDAGP01 | degrees | N/A | - |
*-*-gyro-POSMV_GYRO.gyr
| Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
| heading | degrees | Heading | HEADCM01 | degrees | N/A | - |
*-*-EA600-EA640_DEPTH.EA600
| Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
| depthm | m | Sea floor depth (single-beam) | MBANZZ01 | metres | N/A | - |
*-*-sb_depth-EM120_DEPTH.depth
| Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
| snd | m | Sea floor depth (swath) | MBANSWCB | metres | N/A | - |
All reformatted data were visualised using the in-house EDSERPLO software. Where calibrations had been applied, only the calibrated versions of those parameters were screened. 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). No gaps or speed fails were found.
Distance Run
Distance run was calculated from the main latitude and longitude channels, starting from the beginning of the file, using BODC standard procedures.
GEBCO
GEBCO bathymetry (15 arc-second grid) was added to the file using the main latitude and longitude channels. It was used to screen echo-sounder bathymetry.
Bathymetry
Bathymetry data were screened independently as well as against GEBCO bathymetry measurements. The EM122 was considered the source of bathymetric data during DY116 and was retained in the file.
Calibration
No field calibrations were applied to the data at BODC.
Project Information
Marine LTSS: CLASS (Climate Linked Atlantic Sector Science)
Introduction
CLASS is a five year (2018 to 2023) programme, funded by the Natural Environment Research Council (NERC) and extended until March 2024.
Scientific Rationale
The ocean plays a vital role in sustaining life on planet Earth, providing us with both living resources and climate regulation. The trajectory of anthropogenically driven climate change will be substantially controlled by the ocean due to its absorption of excess heat and carbon from the atmosphere, with consequent impacts on ocean resources that remain poorly understood. In an era of rapid planetary change, expanding global population and intense resource exploitation, it is vital that there are internationally coordinated ocean observing and prediction systems so policy makers can make sound evidence-based decisions about how to manage our interaction with the ocean. CLASS will underpin the UK contribution to these systems, documenting and understanding change in the marine environment, evaluating the impact of climate change and effectiveness of conservation measures and predicting the future evolution of marine environments. Over the five-year period CLASS will enhance the cost-effectiveness of observing systems by migrating them towards cutting edge autonomous technologies and developing new sensors. Finally, CLASS will create effective engagement activities ensuring academic partners have transparent access to NERC marine science capability through graduate training partnerships and access to shipborne, lab based and autonomous facilities, and modelling capabilities.
Data Activity or Cruise Information
Cruise
| Cruise Name | DY116 |
| Departure Date | 2020-11-10 |
| Arrival Date | 2020-11-26 |
| Principal Scientist(s) | Andrew R Gates (National Oceanography Centre, Southampton) |
| Ship | RRS Discovery |
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 |
