Metadata Report for BODC Series Reference Number 1774274
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
Data Description |
|||||||||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||
Data Identifiers |
|||||||||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||
Time Co-ordinates(UT) |
|||||||||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||
Spatial Co-ordinates | |||||||||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||
Parameters |
|||||||||||||||||||||||||||||||||||||||||
|
|||||||||||||||||||||||||||||||||||||||||
|
Problem Reports
No Problem Report Found in the Database
RRS James Cook cruise JC102 underway navigation and bathymetry quality 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. The channel had widely varying interval times, which has resulted in many null values due to the data being averaged to 30s intervals.
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.
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 JC102 underway navigation instrumentation
Instrumentation
The following scientific navigational and bathymetric systems were fitted.
Manufacturer | Model | Function | Comments |
Applanix | RTK POSMV 320 V5 | GPS (lat,lon, heading) | Primary source of position for science. Most precise source of heading. |
Kongsberg Maritime | Simrad EA600 | Single-beam echo sounder (hull) | |
Kongsberg Maritime | Simrad EM120 | Multi-beam echo sounder (deep) |
RRS James Cook cruise JC102 underway navigation processing
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-hhmmss-position-Applanix_GPS_JC1.gps | Position (latitude and longitude) (from POSMV 320) | NetCDF | ~ 1 sec. | 07/04/2014 02:23:52 | 20/04/2014 09:00:01 | - |
yyyymmdd-hhmmss-gyro-GYRO1_JC1.gyr | True heading (from POSMV 320) | NetCDF | ~ 1 sec. | 07/04/2014 02:24:07 | 20/04/2014 09:00:01 | Cleanest and most accurate source of heading from the ship's gyros |
yyyymmdd-hhmmss-EA600-EA600_JC1.EA600 | Depths from central beam EA600 single-beam echosounder | NetCDF | ~ 1-16 sec. | 07/04/2014 02:38:56 | 20/04/2014 09:00:00 | Un-corrected for local sound velocity. Cleanest version of bathymetry |
yyyymmdd-hhmmss-sb_depth-EM120_JC1.depth | Depths from central beam EM120 multi-beam echosounder | NetCDF | - | - | - | No data logged |
BODC Data Processing
Data were banked at BODC following standard banking procedures. Data were averaged to 30 second intervals.
The originator's variables were mapped to appropriate BODC parameter codes as follows:
yyyymmdd-hhmmss-position-Applanix_GPS_JC1.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-hhmmss-gyro-GYRO1_JC1.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-hhmmss-EA600-EA600_JC1.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 echo-sounder |
depthft | feet | Depth in feet | Not transferred | |||
time | days since 1899-12-30 00:00:00 UTC | acquisition time | Not transferred |
yyyymmdd-hhmmss-sb_depth-EM120_JC1.depth
Originator's variable | Originator's units | Description | BODC Code | BODC Units | Unit conversion | Comments |
snd | metre | Sounding value at given frequency. | MBANSWCB | Metres |
No data were logged by the EM120.
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 to identify gaps in the latitude and longitude data. One gap was identified with a duration of 5.000000e-01 minutes (Start: 2014/04/09 17:08:30 End: 2014/04/09 17:13:30). This gap was filled using linear interpolation.
The Applanix POSMV system is the vessel's primary GPS system, outputting the position of the ship's common reference point in the gravity meter room.
Ship Velocities
Ship velocities were calculated from the main latitude and longitude channels at BODC. Some spikes were identified and have been flagged.
Bathymetry
Bathymetry data were screened independently as well as against GEBCO bathymetry measurements. There are breaks in the data due to the acoustic instrumentation being isolated during OBS and AutoSub deployment and recovery. The EA600 was used with a constant sound velocity of 1500 ms-1 throughout the water column. The echo-sounder was not corrected for sound velocity.
Calibration
No field calibrations have been applied to the data at BODC.
Project Information
Role and extent of detachment faulting at slow-spreading mid-ocean ridges
This is a 6 year project that aims to determine (1) the sub-surface geometry and extent of the detachments beneath the ridge axis, (2) the amount and detailed distribution of magmatic crust, and (3) the asymmetry of spreading rates associated with oceanic core complexes and the volcanic seafloor.
The research aims to make an improvement in our overall understanding of the nature and geometry of ocean detachments.
This project was funded by Natural Environment Research Council parent and child grants NE/J022551/1, NE/J02029X/1, and NE/J021741/1 led by Professor Tim Reston at the University of Birmingham, Professor Christine Pierce at Durham University, and Professor Chris MacLeod at Cardiff Univserity respectively. The project is funded from April 2013 to August 2020.
Data Activity or Cruise Information
Cruise
Cruise Name | JC102 |
Departure Date | 2014-04-06 |
Arrival Date | 2014-04-18 |
Principal Scientist(s) | Christine Peirce (University of Durham, Department of Earth 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 |