Metadata Report for BODC Series Reference Number 1836870
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 Clark Ross Cruise JR16001 (AMT26) Surface Hydrography Data Quality Document
Temperature, conductivity, salinity and sound velocity
Unrealistic values in the salinity, conductivity, temperature and sound velocity channels were flagged as improbable. There are several instances in the time series where the surface underway system was switched off. These instances can be identified by a sudden change in values of each parameter followed by sensor drift and then a switch back to previous values. These periods of data have been flagged. There is a drop in values present in all the above hydrography channels on 26/10/2016 from around 12:50 to 15:10. This time frame corresponds to the crossing of a possible front in the water column.
The second hull temperature sensor consistently recorded values of zero throughout the time series and therefore, the primary hull temperature sensor should be used in preference.
Beam transmission and attenuance
The transmittance and attenuance channels are noisy in places and spikes in the channels have been flagged to clean up the noise. There are several instances in the time series where the surface underway system was switched off. These instances can be identified by a sudden change in transmittance and attenuance values and have been flagged. There is a sudden change in the values at around 21/10/2016 13:44 following a cleaning event, after which values become more variable. Prior to this, the channel seems to arbitrarily decline, indicating possible trapped bubbles before cleaning. As it is unclear whether parts of this channel are improbable, the data have been left unflagged and BODC advise the user to use this channel with caution.
Fluorescence
The fluorescence channel was recording unrealistic values throughout the duration of the cruise. The whole channel has been flagged and should be considered as improbable due to the unreliable nature of the current fluorometer on the JCR.
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 EA600 Single Beam Echosounder
The EA600 is a single beam 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 components of the system are hull-mounted transducers linked to general purpose transceivers (GPTs). Up to four GPTs, each controlling one or more transducers, may be operated simultaneously. The GPT generates a signal, which is transmitted into the water column as an acoustic pulse by the transducer array, and the returning echo is recorded by the GPT. GPTs are in turn linked to a combined display and processor, where adjustments (such as sound-speed corrections) may be applied to the data. Available frequencies span from 12 to 710 kHz, and each GPT may operate at a separate frequency. A variety of transducers is available for water depths up to 11,000 m.
The EA600 stores all data internally but has a USB port which allows the possibility of connecting a CD-ROM/DVD drive to read and write the data. All echo data can be stored as files: bitmap, sample, depth or sidescan data.
In deeper waters, the EA600 supports a multipulse function, allowing for a higher pinger rate. While on passive mode, the pinger is normally attached to a device, with the purpose of tracking and displaying its current depth.
The EA600 replaced the EA500 in 2000.
Specifications
| Maximum Ping rate | 20 Hz |
| Resolution | 1 cm |
| Accuracy | 1 cm at 710 and 200 kHz |
| Operating frequencies | 1 or 2 kHz |
| Single Beam frequencies | 12, 18, 33, 38, 50, 70, |
| Dynamic range | 160 dB |
Further details can be found in the manufacturer's specification sheet.
Kongsberg Seatex Seapath 320+ Precise Heading, Attitude and Positioning Sensor
The Seapath 320+ is a navigational system that combines two Global Navigation Satellite System (GNSS) receivers with a MRU 5+ inertial sensor to provide high resolution and accuracy positional data. The inertial sensor employs linear accelerometers and unique microelectromechanical systems (MEMS)-type angular rate gyros to provide 0.01 RMS pitch and roll accuracy. The GNSS receivers can use multiple satellite constellations (GPS, GLONASS and Galileo, when available), and combine data from these to improve heading and positional measurements. In case of missing data from one GNSS receiver, the other receiver provides position and velocity, and the inertial sensor provides heading from its internal rate sensors.
The main characteristics are presented below, and the specification sheet can be accessed here Kongsberg Seatex Seapath 320+ .
Specifications
| Heading accuracy | 0.04° RMS (4m baseline) 0.065° RMS (2.5 baseline) |
| Roll and pitch accuracy | 0.02° RMS for ± 5° amplitude |
| Scale factor error in roll, pitch and heading | 0.05% RMS |
| Heave accuracy (real time) | 5 cm or 5%, whichever is highest |
| Heave accuracy (delayed signal) | 2 cm or 2%, whichever is highest |
| Heave motion periods (real time) | 1 to 20 seconds |
| Heave motion periods (delayed signal) | 1 to 50 seconds |
| Position accuracy (DGPS/DGlonass) | 1 m (95% CEP) |
| Position accuracy (SBAS) | 1 m (95% CEP) |
| Position accuracy (with RTK corrections) | 0.2 m (95% CEP) |
| Velocity accuracy | 0.07 m s-1 (95% CEP) |
| Data update rate | Up to 100Hz |
RRS James Clark Ross cruise JR16001 (AMT26) navigation instrumentation
The following scientific navigational and bathymetric systems were fitted.
| Manufacturer | Model | Function | Comments |
| Seatex | Seapath 320+ | GPS (latitude, longitude) | Primary source of position for science. |
| Kongsberg Maritime | Simrad EA600 | Single-beam echo sounder (hull) | Best quality bathymetry source |
| Kongsberg Maritime | Simrad EM120 | Multi-beam echo sounder (deep) | |
| Sperry Marine | MK37 series gyrocompasses | GPS (ships heading) | The gyro.ACO file received from BAS did not contain any heading data, only date and time information. Heading data are unavailable for this cruise. |
RRS James Clark Ross Cruise JR16001 (AMT26) Navigation and Bathymetry Processing Procedures Document
Originator's Data Processing
The navigation and bathymetric data were measured by several different instruments and the data were logged every second to the SCS system and stored in comma separated ACO format. Each instrument logged data to one individual file and the associated header information is stored in TPL files.
The originator's data files exhibited the same common format for the first four columns: Year (yyyy), Julian day.day fraction (days), Julian day (days), day fraction (days). The remaining columns contain the actual data values.
The table below shows the original files delivered to BODC that contained the data in the final data series, along with start and end dates and times of each file.
| Filename | Content Description | Format | Interval | Start date | Start Time | End date | End Time |
| seatex-gga.ACO | Latitude and Longitude | ASCII (.ACO) | 1 sec | 17/09/2016 | 09:00:46 | 03/11/2016 | 15:33:52 |
| gyro.ACO | Ships Heading | ASCII (.ACO) | ~ 1 sec | 22/09/2016 | 15:01:40 | 03/11/2016 | 15:33:52 |
| ea600.ACO | Single-beam echo-sounder | ASCII (.ACO) | ~ 2 secs | 17/09/2016 | 09:00:46 | 03/11/2016 | 15:33:50 |
| em122.ACO | Multi-beam echo-sounder | ASCII (.ACO) | ~ 10 secs | 26/09/2016 | 14:33:55 | 30/09/2016 | 05:19:39 |
BODC Data Processing
The ACO files provided by the originator were transferred into internal BODC format using established BODC data banking procedures. The data were averaged to 60 second intervals. The originators files contained many parameters that were not transferred because they were not relevant to the final data set and several channels were derived by BODC.
The table below provides a description of the originators channels transferred, along with the BODC parameter codes and units assigned. BODC processing procedures then included reduction through averaging, checking navigation channels for improbable values, working out speed over ground, and screening the data for anomalous values.
| Originator's File | Originator's Parameter | Originator's Units | Description | BODC parameter | BODC Units | Comments and unit conversions |
|---|---|---|---|---|---|---|
| seatex-gga.ACO | lat | Degrees (+ve N) | Latitude north (WGS84) by Seatex Seapath DGPS | ALATGP01 | Degrees (+ve N) | - |
| seatex-gga.ACO | lon | Degrees (+ve E) | Longitude east (WGS84) by Seatex Seapath DGPS | ALONGP01 | Degrees (+ve E) | - |
| - | - | - | Distance traveled | DSRNCV01 | meters | Channel derived using Matlab routine from Seatex navigation channels |
| gyro.ACO | heading | degrees | Orientation (horizontal relative to true north) of measurement platform {heading} by compass | HEADCM01 | degrees | The gyro during the cruise did not log any heading data. The gyro.ACO file provided to BODC only contained date and time information and no heading data was recorded, so is not available for this cruise. |
| - | - | - | Eastward velocity (over ground) of measurement platform by unspecified GPS system | APEWGP01 | cm s-1 | Channel derived after transfer using BODC Matlab routine 'velcal' |
| - | - | - | Northward velocity (over ground) of measurement platform by unspecified GPS system | APNSGP01 | cm s-1 | Channel derived after transfer using BODC Matlab routine 'velcal' |
| ea600.ACO | depth | m | Sea-floor depth (below instantaneous sea level) {bathymetric depth} in the water body by echo sounder | MBANZZ01 | meters | Best quality bathymetry channel |
| em122.ACO | depth | meters | multi-beam depth by echo-sounder | MBANSWCB | meters | - |
Navigation channels
Latitude and longitude channels were checked and the best quality channels were from the seatex.ACO file. A check was run and six gaps in the navigation channels were identified. Two of these were at the start and end of the file and were trimmed off the data streams. The remaining gaps were all less than 30 minutes so were filled by interpolation. The speed check fails resulted from four erroneous data values in the latitude and longitude channels. These spikes were flagged null and the resulting gaps filled by interpolation.
- Gap 1 Start: 2016/09/16 00:00:00 End: 2016/09/17 09:00:00 Duration: 1981 minutes
- Gap 2 Start: 2016/09/22 12:26:00 End: 2016/09/22 12:26:00 Duration: 1 minutes
- Gap 3 Start: 2016/09/22 12:35:59 End: 2016/09/22 12:35:59 Duration: 1 minutes
- Gap 4 Start: 2016/09/22 12:40:00 End: 2016/09/22 12:41:59 Duration: 3 minutes
- Gap 5 Start: 2016/09/22 13:21:59 End: 2016/09/22 13:23:00 Duration: 2 minutes
- Gap 6 Start: 2016/11/03 15:35:00 End: 2016/11/04 00:00:00 Duration: 506 minutes
- Speed check fail. Speed = 58143.5 m/s on 2016/09/22 12:38:00
- Speed check fail. Speed = 95716.8 m/s on 2016/09/22 12:43:59
- Speed check fail. Speed = 39987.3 m/s on 2016/09/22 13:25:00
- Speed check fail. Speed = 22396.7 m/s on 2016/09/22 13:28:59
- Speed check fail. Speed = 22396.7 m/s on 2016/09/22 13:30:00
Distance Run
Distance run was re-derived using the seatex latitude and longitude channels using the BODC Matlab utility 'disrun'.
Ship velocities
The ship's north and east velocities were re-derived using the seatex latitude and longitude channels, using the BODC Matlab routine 'velcal'.
Bathymetry
Bathymetry data were screened independently as well as against GEBCO bathymetry measurements. Bathymetry data from the EA600 single-beam echo-sounder were deemed to be the best quality. The multi-beam echo-sounder was switched on later and turned off earlier than the single-beam and so is a shorter time series of data.
Calibration
No sample calibrations were applied to these data.
Project Information
No Project Information held for the Series
Data Activity or Cruise Information
Cruise
| Cruise Name | JR16001 (AMT26) |
| Departure Date | 2016-09-20 |
| Arrival Date | 2016-11-04 |
| Principal Scientist(s) | Andrew Rees (Plymouth Marine Laboratory) |
| 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 |
| B | nominal value |
| Q | value below limit of quantification |
