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Processing and Quality Checks of Shipboard ADCP

Processing and Quality Checks of Shipboard ADCP. Michèle FICHAUT, IFREMER/SISMER. Ship and Equipment. Three IFREMER Ships L’ATALANTE : NB 75 and NB 300 THALASSA : NB75 and BB 150 SUROÎT : BB 150 One Hydrographic Office Ship BEAUTEMPS-BEAUPRE : NB 38 and BB 150. Data transmission.

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Processing and Quality Checks of Shipboard ADCP

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  1. Processing and Quality Checks of Shipboard ADCP Michèle FICHAUT, IFREMER/SISMER

  2. Ship and Equipment • Three IFREMER Ships • L’ATALANTE : NB 75 and NB 300 • THALASSA : NB75 and BB 150 • SUROÎT : BB 150 • One Hydrographic Office Ship • BEAUTEMPS-BEAUPRE : NB 38 and BB150

  3. Data transmission • Since 2001, standard configuration on the IFREMER vessels • Raw data at SISMER at the end of the cruise • Errors 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 cruise • But errors in the acquisition can be detected on the first file and corrected directly onboard

  4. 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 calculation • Quality checks of the data

  5. Quality checks of the data • Flags are attributed to the numerical values automatically and visually (flag 9)

  6. Inconsistent values -> Flag 9 Example of QC • Cruise of the BEAUTEMPS-BEAUBRE in the Red Sea , Aden Gulf and Oman Sea • Corresponding quality flags for the whole cruise

  7. Presentation of the data • For one cruise, one or several sections are defined 4 1 3 2

  8. Images of the sections • Section 1, in the Red Sea • E/W horizontal current speed component • N/S horizontal current speed component • Current vertical speed

  9. Whole cruise’s vector plots • 0 – 100 m • 100 – 300 m

  10. Section’s vector plots • Eddies in the superficial water (0-100m and 100-300m) • Current aligned on the central valley in the deepest part (300-600 m)

  11. Detected errors • Errors detected at the beginning of data processing : • ADCP time is wrong and cannot be related to the navigation • Raw 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 processing • Strong correlation between current speed and ship velocity • Unrealistic current vectors

  12. Example of wrong data (1) • Detected with correlation between ship velocity and current speed

  13. Example of wrong data (2) • Detected with section’s vector plots

  14. Data distribution • Since 2001 : 49 IFREMER cruises (21 processed), 3 SHOM cruises (all processed)

  15. Data volume • 52 cruises : • Raw data : 49 Gigabytes • ~= 1 gigabyte per cruise • Data dissemination : • between 1 to 100 Mb per cruise

  16. Provinding data • One NetCDF file per cruise • Date/time, Latitude, Longitude, Depth, N/S, E/W , Vertical current speed, Echo intensity • One tar file with figures • Section map, images and vector plots of the sections • One report • Information about data collection • Information about the quality checks and the processing procedures • Any problem encountered with the data

  17. 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 ?

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