Metadata Report for BODC Series Reference Number 1760660


Metadata Summary

Data Description

Data Category Bathymetry
Instrument Type
NameCategories
Simrad EA500 echosounder  single-beam echosounders
Kongsberg (Simrad) EM 120 multibeam echosounder  multi-beam echosounders
Kongsberg Seatex Seapath 200 Global Positioning System receiver and Gyrocompass  platform attitude sensors; Differential Global Positioning System receivers
Instrument Mounting research vessel
Originating Country United Kingdom
Originator Dr Stuart Painter
Originating Organization National Oceanography Centre, Southampton
Processing Status banked
Project(s) Oceans 2025 Theme 10 SO1:AMT
 

Data Identifiers

Originator's Identifier JR20081003_PRODQXF_NAV
BODC Series Reference 1760660
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 2008-10-03 09:25
End Time (yyyy-mm-dd hh:mm) 2008-11-09 15:30
Nominal Cycle Interval 60.0 seconds
 

Spatial Co-ordinates

Southernmost Latitude 49.17300 S ( 49° 10.4' S )
Northernmost Latitude 53.62680 N ( 53° 37.6' N )
Westernmost Longitude 53.82150 W ( 53° 49.3' W )
Easternmost Longitude 0.18890 W ( 0° 11.3' W )
Positional Uncertainty 0.0 to 0.01 n.miles
Minimum Sensor Depth -
Maximum Sensor Depth -
Minimum Sensor Height -
Maximum Sensor Height -
Sea Floor Depth -
Sensor Distribution -
Sensor Depth Datum -
Sea Floor Depth Datum -
 

Parameters

BODC CODE Rank Units Short Title Title
AADYAA01 1 Days Date(Loch_Day) Date (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ01 1 Days Time(Day_Fract) Time (time between 00:00 UT and timestamp)
ALATGP01 1 Degrees Lat_GPS Latitude north (WGS84) by unspecified GPS system
ALONGP01 1 Degrees Lon_GPS Longitude east (WGS84) by unspecified GPS system
APEWGP01 1 Centimetres per second PlatformVelE_GPS Eastward velocity (over ground) of measurement platform by unspecified GPS system
APNSGP01 1 Centimetres per second PlatformVelN_GPS Northward velocity (over ground) of measurement platform by unspecified GPS system
DSRNCV01 1 Kilometres Cmpval Distance travelled
HEADCM01 1 Degrees Platform_Heading Orientation (horizontal relative to true north) of measurement device {heading}
MBANSWCB 1 Metres SwathCBBathyDep Sea-floor depth (below instantaneous sea level) {bathymetric depth} in the water body by multibeam echo sounder central beam
 

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

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°
1° x 2°
2° x 2°
2° x 4°

Beam spacing (at angular coverage)

1% of depth at 90°
2% of depth at 120°
3% of depth at 140°

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.

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:

The specific objectives are:

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