MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Processing and Quality Checks of Shipboard
ADCP
Michèle FICHAUT, IFREMER/SISMER
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Ship and Equipment
Three IFREMER ShipsL’ATALANTE : NB 75 and NB 300 THALASSA : NB75 and BB 150SUROÎT : BB 150
One Hydrographic Office ShipBEAUTEMPS-BEAUPRE : NB 38 and BB 150
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Data transmission
Since 2001, standard configuration on the IFREMER vessels
Raw data at SISMER at the end of the cruiseErrors in the acquisition are detected when processing the data
Since 2004, Beautemps-Beaupré transmits ADCP data each day in real time
Data are processed at the end of the cruiseBut errors in the acquisition can be detected on the first file and corrected directly onboard
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Processing
Software CASCADE developed in IFREMER by the Laboratory of Physical Oceanography (Matlab)4 steps for the processing :
Reformatting raw data into NetCDF Generation of processed files (attitude and time corrections, calculation of terrestrial coordinates, filtering, means)Ground speed calculationQuality checks of the data
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Quality checks of the data
Flags are attributed to the numerical values automatically and visually (flag 9)
1 Good data2 Doubtf ul data (out liers)3 Spikes4 Gradient > 0.05 cm/ s5 Vert ical current speed > 30 cm/ s6 Horizontal current speed component > 4 m/ s7 Missing data8 Data under the bottom (bottom ping)9 Data visually rejected (inconsistent)
10 Data under the bottom (compared to gridded bathymetry)
ADCP1 Good2 Probably good3 Doubtf ul4 False5 Modifi ed6 Not used7 Not used8 Not used9 Missing value
GTSPP
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Example of QC
Cruise of the BEAUTEMPS-BEAUBRE in the Red Sea , Aden Gulf and Oman Sea
Corresponding quality flags for the whole cruise
Inconsistent values -> Flag 9
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Presentation of the data
For one cruise, one or several sections are defined
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Images of the sections
Section 1, in the Red Sea
E/W horizontal current speed componentN/S horizontal current speed componentCurrent vertical speed
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Whole cruise’s vector plots
0 – 100 m 100 – 300 m
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Section’s vector plotsEddies in the superficial water (0-100m and 100-300m)Current aligned on the central valley in the deepest part (300-600 m)
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Detected errors
Errors detected at the beginning of data processing :
ADCP time is wrong and cannot be related to the navigationRaw data files are too big to be processed by the software : typically the standard procedure is one raw data file per one day of cruise maximum (12 hours is the optimal size).
Errors detected after data processingStrong correlation between current speed and ship velocityUnrealistic current vectors
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Example of wrong data (1)
Detected with correlation between ship velocity and current speed
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Example of wrong data (2)
Detected with section’s vector plots
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Data distributionSince 2001 : 49 IFREMER cruises (21 processed), 3 SHOM cruises (all processed)
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Data volume
52 cruises : Raw data : 49 Gigabytes ~= 1 gigabyte per cruise
Data dissemination : between 1 to 100 Mb per cruise
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Provinding data
One NetCDF file per cruiseDate/time, Latitude, Longitude, Depth, N/S, E/W , Vertical current speed, Echo intensity
One tar file with figuresSection map, images and vector plots of the sections
One reportInformation about data collectionInformation about the quality checks and the processing proceduresAny problem encountered with the data
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lfremer
MAY 3-5 2004 ICES – MDM 2004, BRUSSELS
Conclusive remarks and questions
Not fully compliant with MDM guidelines for ADCP:
Dissemination format is NetCDF in stead of ASCII
There is no international exchange for ADCP data :
Is it worth doing one?What about the WDCA ?
What do other members do with ADCP shipboard data if they have some ?