Metadata Report for BODC Series Reference Number 1760660
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 JR20081003 (AMT18) Navigation Quality Control Report
Quality control report
Navigation
The Matlab routine 'navcheck' raised issues with the speed <10 ms-1 for the period 03/10/2008 10:20 to 10:33. Checking the lat and long channels showed no unusual spikes to be flagged. This was shortly after departure and could be possible if there was an outgoing tide at time of departure. The speed (over ground) data should be regarded as slightly suspect this early in the cruise as the speed holds constant for a period then jumps above 10 ms-1 before dropping.
Velocity channels
North and south velocity channels were flagged 'M' for the period 03/10/2008 1010-1040; consecutive constant values then a jump to high speeds (flagged in 'navcheck'), which may be possible with a flood tide
Bathymetry
The multi-beam bathymetry channel has been flagged throughout the cruise where noise in the channel moves away from the baseline bathymetry. A number of individual data points spiking from 1000s m up to 5-6 m have been flagged as improbable. Also a number of deeper spikes have been flagged improbable. Null data was received for the periods 06/10/2008 20:00 to 07/10/2008 09:30, 10/10/2008 14:45-18:30, 11/10/2008 12:30-15:45 and 24/10/2008 09:00-11:30.
Heading
The period 1809-1850 on 31/10/2008 was flagged as suspect. There is a concurrent break in the latitude and longitude channels, which have since been interpolated, for the first 10 minutes of this period, these are flagged null in this channel. The remaining 30 minutes data combined with the course made good (cmg) heading data suggest the vessel switched through 180 degrees and carried on the same course in reverse then switched back through 180 degrees without significant change in the cmg heading so this period has been flagged 'M'. In addition a small number of individual data points were flagged 'M' where the heading spiked while otherwise steaming between sampling stations.
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.
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.
Specifications
| 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.
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 .
Specifications
| Scale factor error in pitch, roll and heading | 0.2% RMS |
| Heave motion periods | 1 to 25 s |
| Accuracy | |
| Heading | 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 |
| Position | 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 |
RRS James Clark Ross Cruise JR20081003 (AMT18) Navigation Instrumentation
The navigation instruments used to generate this dataset are displayed in the table below. Sensors have been identified where possible from the BAS JCR data dictionary and a list of underway sensors that were present on the JCR at the start of 2008, which have been provided to BODC by BAS.
| Instrument Manufacturer | Model | Main Function |
| Seatex | Seapath 200 | Ship's position |
| Simrad Kongsberg | EA500 | Bathymetry by single-beam echo-sounder |
| Kongsberg | EM120 | Bathymetry by multi-beam echo-sounder |
RRS James Clark Ross Cruise JR20081003 (AMT18) Navigation Data Processing Procedures
Originator's Data Processing
Navigational data were available from different GPS systems (Glonass, Ashtec, etc) on the James Clark Ross. These were processed on board and the ship's best determined position was calculated by the NMF process 'bestnav' to produce a 30 second average ship's position. The 'bestnav' data stream represents the combined output from several sensors to ensure the continuous navigation information in the event of one sensor failing. The main source of data was the ship's GPS SeaTex system, which is regarded to provide the most accurate position. The 'bestnav' data stream was transferred daily into the PSTAR absolute navigation file 'abnv2181' for use in PSTAR processing during the cruise. It was noted that the navigation data stopped before the ship reached its destination port. Last record in file was on 2008/11/09 15:30:00.
The table below shows the original files delivered to BODC that contained the data in the final data series.
| Filename | Parameters in file | Format | Interval | Start date | Start Time | End date | End Time |
| abnv2181 | latitude, longitude, eastward velocity, northward velocity, course made good, speed made good, distance run, heading | PSTAR | 30 seconds | - | - | - | - |
| em120.lst | Multi-beam echo-sounder | RVS | 2 to 25 seconds | 04/10/2008 | 12:29:48 | 09/11/2008 | 16:10:57 |
| sim500.lst | Single-beam echo-sounder | RVS | 2 to 7 seconds | 02/10/2008 | 17:44:02 | 09/11/2008 | 16:10:55 |
BODC Data Processing
Navigation data from processed PSTAR format files, along with wind measurements and bathymetry (em120 and sim500) from the full-resolution 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.
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 |
|---|---|---|---|---|---|---|
| abnv2181 | lat | Degrees (+ve N) | Latitude north (WGS84) by Seatex Seapath DGPS | ALATGP01 | Degrees (+ve N) | - |
| abnv2181 | lon | Degrees (+ve E) | Longitude east (WGS84) by Seatex Seapath DGPS | ALONGP01 | Degrees (+ve E) | - |
| - | - | - | Distance traveled | DSRNCV01 | km | Channel derived using Matlab routine from Seatex navigation channels |
| abnv2181 | heading | degrees | Orientation (horizontal relative to true north) of measurement platform {heading} by compass | HEADCM01 | degrees | - |
| abnv2181 | ve | cm s-1 | Eastward velocity (over ground) of measurement platform by unspecified GPS system | APEWGP01 | cm s-1 | - |
| abnv2181 | vn | cm s-1 | Northward velocity (over ground) of measurement platform by unspecified GPS system | APNSGP01 | cm s-1 | - |
| abnv2181 | cmg | Degrees true | Northward velocity (over ground) of measurement platform by unspecified GPS system | APDAGP01 | Degrees true | Channel not transferred |
| abnv2181 | smg | m s-1 | Northward velocity (over ground) of measurement platform by unspecified GPS system | APSAGP01 | m s-1 | Channel not transferred |
| sim500.lst | depth | m | Sea-floor depth (below instantaneous sea level) {bathymetric depth} in the water body by echo sounder | MBANZZ01 | meters | Channel not transferred |
| em120.lst | depth | meters | multi-beam depth by echo-sounder | MBANSWCB | meters | - |
Navigation channels
Once the PSTAR navigation files compiled after from the 'bestnav' files were converted 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 (<15 minutes) in the latitude and longitude channels, these were filled using the Matlab program 'navint' to interpolate data to fill the gaps. Gaps 1 and 5 were at the start and end of the file and trimmed off. In addition there were a few speed check failures in the navigation data, where speed over ground was higher than might be expected. This occurred at the start of the cruise and could well be possible given a flood tide at departure.
- Gap 1 Start: 2008/10/01 00:00:00 End: 2008/10/01 13:34:59 Duration: 816 minutes
- Gap 2 Start: 2008/10/03 09:45:00 End: 2008/10/03 09:45:00 Duration: 1 minutes
- Gap 3 Start: 2008/10/04 12:54:00 End: 2008/10/04 12:54:00 Duration: 1 minutes
- Gap 4 Start: 2008/10/31 18:09:00 End: 2008/10/31 18:19:00 Duration: 11 minutes
- Gap 5 Start: 2008/11/09 15:30:59 End: 2008/11/13 00:00:00 Duration: 4830 minutes
Distance Run
Distance run was re-derived using the seatex latitude and longitude channels using the BODC Matlab utility 'disrun'.
Bathymetry
Bathymetric data were loaded from two RVS files em120.rvs and sim500.rvs. These contained the logged output from the EM120 multibeam swath bathymetry centrebeam depth (em120) and the Simrad-ea500 depth measurement (sim500). As part of the screening process a channel was added for the bathymetry derived from GEBCO. This data is often of lower resolution than that available along the cruise track from on board sensors but provided a background bathymetry with which to screen the channels recorded during the cruise for unrealistic data values. The multi-beam bathymetry channel was deemed to be the best quality.
Screening
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 ('M' for suspect value). 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.
Calibration
No sample calibrations were applied to these data.
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:
- give early warning of any fundamental change in Atlantic ecosystem functionng
- improve forecasts of the future ocean state and associated socio-economic impacts
- provide a "contextual" logistical and scientific infrastructure for independently-funded national and international open ocean biogeochemical and ecological research.
The specific objectives are:
- To collect hydrographic, chemical, ecological and optical data on transects between the UK and the Falkland Islands
- To quantify the nature and causes of ecological and biogeochemical variability in planktonic ecosystems
- To assess the effects of variability in planktonic ecosystems on biogenic export and on air-sea exchange of radiatively active gases
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
Weblink: http://www.oceans2025.org/
Data Activity or Cruise Information
Cruise
| Cruise Name | JR20081003 (AMT18, JR218) |
| Departure Date | 2008-10-03 |
| Arrival Date | 2008-11-10 |
| Principal Scientist(s) | E Malcolm S Woodward (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 |
| Q | value below limit of quantification |
