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Tidal Data Processing

Tidal Data Processing. Data Flow. WL Station data origin and path to DMS Decode and Unpack QC process (behind the scenes) Moving data from Sensor Areas into Working WL Table Editing data (behind the scenes) Tabulate, creating Hourly Heights and Highs/Lows Compute Monthly Means

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Tidal Data Processing

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  1. Tidal Data Processing

  2. Data Flow • WL Station data origin and path to DMS • Decode and Unpack • QC process (behind the scenes) • Moving data from Sensor Areas into Working WL Table • Editing data (behind the scenes) • Tabulate, creating Hourly Heights and Highs/Lows • Compute Monthly Means • Compute Datums

  3. Observed Data to Tidal Datums Data to Datums Tidal Datums Team nos.coops.datums@noaa.gov RAW SIX-MINUTE WATER LEVEL Verified Monthly Means ACCEPTED Datums Verified HI / LO Verified SIX-MINUTE WATER LEVEL Verified WATER LEVEL HOURLY http://tidesandcurrents.noaa.gov/station_retrieve.shtml?type=Datums

  4. Data Processing Procedures: Preliminary • Preliminary Data Analysis • Tabulation • Monthly Means • Verification

  5. The Automated QC Process • Automated QC Performs the following actions: • Compares sensor and datum offsets to the existing values, inserts if different • Acoustic: Check soundpath air temperatures • Acoustic: Compute height differences based on temperature gradients, sets flags, apply appropriate correction if necessary • Acoustic: Compares Primary WL with Backup WL, Predicted WL, and Nearby Station WL • Checks for excessive Rate-of-Change • Creates time series for Acoustic data

  6. The Automated QC Process • QA Performs the following actions: • Backup Water Level: Check tolerances, check for flats, set flags, create time series • Pressure Data (T1, N1, NT): check tolerances, check for flats, set flags, check Third Difference, create time series • Ancillary sensors : check tolerances (max/min), create time series • Insert data into database tables for each data type • Update time series for each data type in database tables

  7. Move Data from Sensor Tables into Working Water Level (Initialize) ACOUSTIC ACCEPTEDWATER LEVEL Initialize A1, V1, N1, NT BACKUP B1 sensor Copy N1, Tx, NT sensor PRESSURE Merge Time Series ACCEPTED WATER LEVEL SERIES WL TIME SERIES

  8. Data Processing Stages • Preliminary Work • Check station parameters • Examine data inventories • Initialize Working Water Level data • Review 6-minute Data plots • Fill Breaks • Fill-six program or QC Spreadsheet • Use Backup WL data, compatible nearby station data, predictions, or curve fit for small breaks • Perform Offline QC Checks • Check and correct erroneous data using the QC Spreadsheet, nearby station checks

  9. WL Processing on DMS • Plot Primary sensor data and Standard Deviation

  10. WL Processing on DMS • Perform offline QC Checks

  11. Data Processing Procedures: Gap Filling • Curve fit (least squares or linear fit) ≤ 4 hours* • Backup data (B1 usually) • Nearby station ≤ 3 days • Predicted data (PR) NOTE: For gaps larger than 3 days, without backup: DO NOT fill it

  12. Filling the gaps Fill with backup (B1) or nearby station Backup Fill Curve fit Fill with predicted (PR) data

  13. TABULATE Tabulate Function ACCEPTED HI LO ACCEPTED WATER LEVEL ACCEPTED WATER LEVEL TIME SERIES ACCEPTED WATER LEVEL HOURLY

  14. Data Tabulation Stages • Tabulation • Tabulate High and Low waters • Use QC Spreadsheet to edit Hourly Heights and Hi/Lo waters • Plot WL w/ HI/LO picks and corrections • Run Hi/Lo check option • Compute Monthly Means • Mark data Complete • Make output reports • Final Time Series Check

  15. Criteria for determining a Tide • Two-hour rule • One-tenth of a foot rule (same as 0.03 m rule) Difference in time Difference in elevation

  16. 13 EXHL (pairing) Moon at maximum or minimum declination Month 1 2 3 4 5 6 7

  17. 14 DIUR (25-hour algorithm) Tentative Time Point #1 Point #3 Point #2 Time C Time B Time A Month 1 2 3 4 5 6 7 8 9 10 11 11

  18. Data Processing Procedures: Preliminary • Tabulation • Tabulate High /Low waters • Tabulate Hourly Heights • Plot WL w/ HI/LO • Run Hi/Lo check option • Compute Monthly Means

  19. Data Processing Procedures: Preliminary • Large Standard Deviation indicates data issues

  20. Tide check (Report)

  21. Picking Highs / Lows with Strong Tide Signature

  22. Picking Highs / Lows in Low Tidal Signal, Meteorologically Driven System

  23. Questionable tides are evaluated Should be HL

  24. Final Hi / Lo Tide Picks Reviewed

  25. Data Processing Procedures: Final • Review • High /Low waters • Review Hourly Heights • Compute Monthly Means

  26. WL Processing Diagnostic • TABULATION summary

  27. WL Processing Output • Plot of 6-min WL data w/ Hi-Lo and HH-LL picks

  28. WL Processing Output • Printout of WL Hourly Heights

  29. WL Processing Output • Final High/Low Water Level data Report

  30. Monthly Means Computation ACCEPTED HI LO WL Monthly Means ACCEPTED WATER LEVEL MONTHLY ACCEPTED SIX-MINUTE WATER LEVEL ACCEPTED WATER LEVEL HOURLY

  31. WL Processing Output • Monthly Means report

  32. WL Processing Checklist • WL Verification

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