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Overview of the Hydrographic Surveying Pipeline
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  1. Overview of the Hydrographic Surveying Pipeline

  2. WATER LEVEL MEASUREMENTSUPPORT TO HYDROGRAPHIC SURVEY OPERATIONS • Project Planning • Requirements, Desired Accuracies • Budget, Timeframe (In-survey processing, post-processing?) • Station Locations, Configuration and Installation Timeframe • Operations • Station O&M • Data Collection, QC, Processing • Leveling, Bench Mark Network, Geodetic Datum Connections • Tidal Datum Computation • Final Tidal Zoning

  3. ERROR BUDGET CONSIDERATIONS FOR WATER LEVELS • THE WATER LEVEL REDUCER CAN BE THE MOST SIGNIFICANT CORRECTOR TO THE SOUNDINGS • THE COMPONENT OF THE TOTAL ERROR BUDGET DUE TO APPLICATION OF THE WATER LEVEL REDUCERS CAN ALSO BE QUITE SIGNIFICANT • THE ALLOWABLE CONTRIBUTION OF THE ERROR FOR TIDES AND WATER LEVELS TO THE TOTAL SURVEY ERROR BUDGET FALLS BETWEEN 0.20 METERS AND 0.45 METER (95% CONFIDENCE LEVEL) DEPENDING UPON COMPLEXITY OF THE TIDAL REGIME AND THE SURVEY AREA. • THE ERROR BUDGET NEEDS TO BE ESTIMATED IN ADVANCE IN THE PLANNING STAGES SO THAT THE POTENTIAL ERROR IN WATER LEVELS CAN BE APPROPRIATELY BALANCED AGAINST ALL OTHER SURVEY ERRORS IN THE PROJECT DESIGN

  4. ERROR BUDGET CONSIDERATIONS FOR WATER LEVELS THE ALLOWABLE CONTRIBUTION OF THE ERROR FOR TIDES AND WATER LEVELS TO THE TOTAL SURVEY ERROR BUDGET FALLS BETWEEN 0.20 METERS AND 0.45 METER (95% CONFIDENCE LEVEL) DEPENDING UPON COMPLEXITY OF THE TIDAL REGIME AND THE SURVEY AREA AND HAS THREE MAJOR COMPONENTS: • THE MEASUREMENT/PROCESSING ERROR IN COLLECTION OF GAUGE/SENSOR DATA AND THE PROCESSING OF THE DATA. • THE ERROR IN COMPUTATION OF TIDAL DATUMS FOR THE ADJUSTMENT TO A 19-YEAR NATIONAL TIDAL DATUM EPOCH (NDTE) FROM SHORT-TERM STATIONS • THE ERROR IN THE APPLICATION OF TIDAL OR WATER LEVEL ZONING

  5. Corrections to Echo Soundings Dynamic Transducer Draft Correction Tide Correction Reference Datum Observed Depth Actual Depth Chart Depth Sound Velocity Correction

  6. Total allowable error THE ALLOWABLE CONTRIBUTION OF THE ERROR FOR TIDES AND WATER LEVELS TO THE TOTAL SURVEY ERROR BUDGET FALLS BETWEEN 0.20 METERS AND 0.45 METER (95% CONFIDENCE LEVEL)

  7. ERROR BUDGET CONSIDERATIONS FOR WATER LEVELS • THE MEASUREMENT/PROCESSING ERROR IN COLLECTION OF GAUGE/SENSOR DATA AND THE PROCESSING OF THE DATA. • THE MEASUREMENT ERROR SHOULD NOT EXCEED 0.10 METER (95% CONFIDENCE LEVEL) AND INCLUDES ERROR CONTRIBUTIONS FROM: • DYNAMIC EFFECTS OF WAVES, CURRENTS, DENSITY, TEMPERATURE, ETC… ON THE SENSOR • PERFORMANCE/CALIBRATION OF THE WATER LEVEL GAUGE SYSTEM • REFERENCING OF THE SENSOR ZERO TO STATION DATUM THROUGH TIDE STAFFS, LEVELS AND BENCH MARKS • THE PROCESSING ERROR SHOULD NOT EXCEED 0.10 METER (95% CONFIDENCE LEVEL) AND INCLUDES ERROR CONTRIBUTIONS DUE TO DATA SAMPLING RATES AND INTERPOLATION OF THE WATER LEVEL DATA TO THE EXACT TIME OF THE SOUNDINGS

  8. DYNAMIC EFFECTS OF WAVES, CURRENTS, DENSITY, TEMPERATURE, ETC… ON THE SENSOR

  9. PERFORMANCE/CALIBRATION OF THE WATER LEVEL GAUGE SYSTEM

  10. REFERENCING OF THE SENSOR ZERO TO STATION DATUM THROUGH TIDE STAFFS, LEVELS AND BENCH MARKS

  11. THE PROCESSING ERROR SHOULD NOT EXCEED 0.10 METER (95% CONFIDENCE LEVEL) AND INCLUDES ERROR CONTRIBUTIONS DUE TO DATA SAMPLING RATES AND INTERPOLATION OF THE WATER LEVEL DATA TO THE EXACT TIME OF THE SOUNDINGS

  12. ERROR BUDGET CONSIDERATIONS FOR WATER LEVELS • THE ERROR IN COMPUTATION OF TIDAL DATUMS FOR THE ADJUSTMENT TO A 19-YEAR NATIONAL TIDAL DATUM EPOCH (NDTE) FROM SHORT-TERM STATIONS • THE SHORTER THE TIME SERIES, THE LESS ACCURATE THE DATUM • ESTIMATED ERRORS OF AN ADJUSTED TIDAL DATUM BASED UPON ONE MONTH OF TIDE DATA ARE 0.08 METER FOR THE EAST AND WEST COASTS OF THE U.S. AND 0.11 METER FOR THE GULF COAST (95% CONFIDENCE LEVEL) • THE MORE SIMILAR THE SEA LEVEL VARIATIONS AND TIDAL CHARACTERISTICS OF THE SHORT-TERM STATION ARE TO THE CONTROL STATION, THE MORE ACCURATE THE DATUMS • ALTHOUGH TIDAL DATUMS ARE NOT COMPUTED FOR THE GREAT LAKES, THE ERRORS DUE TO SERIES LENGHTS AND CLOSENESS TO CONTROL STATIONS ARE ANALOGOUS

  13. THE SHORTER THE TIME SERIES, THE LESS ACCURATE THE DATUM

  14. THE MORE SIMILAR THE SEA LEVEL VARIATIONS AND TIDAL CHARACTERISTICS OF THE SHORT-TERM STATION ARE TO THE CONTROL STATION, THE MORE ACCURATE THE DATUMS

  15. ERROR BUDGET CONSIDERATIONS FOR WATER LEVELS • THE ERROR IN THE APPLICATION OF TIDAL OR WATER LEVEL ZONING • TIDAL ZONING IS THE EXTRAPOLATION OF AND/OR INTERPOLATION OF TIDAL CHARACTERISTICS FROM A KNOWN SHORE POINT(S) TO A DESIRED SURVEY AREA USING TIME DIFFERENCES AND RANGE RATIOS • FOR THE GREAT LAKES, WATER LEVEL ZONING IS THE INTERPOLATION OF DATUM CORRECTIONS TO THE REFERENCE DATUM DATUM OF IGLD BETWEEN STATIONS AND IS ESPECIALLY SIGNIFICANT IN THE INTERCONNECTING WATERWAYS IN THE LAKES SYSTEM • THE GREATER THE EXTRAPOLATION/INTEROLATION, THE GREATER THE ERROR • ESTIMATES FOR A TYPICAL ERROR ASSOCIATED WITH TIDAL ZONING ARE 0.20 METER (95% CONFIDENCE LEVEL) • TIDAL ZONING EERRORS CAN DOMINATE THE ERROR BUDGET IN AREAS OFCOMPLEX AND ILL-DEFINED TIDAL REGIMES AND IN AREAS WHICH METEROROLGICAL FORCING DOMINATES THE TIDE. IN THESE SITUATIONS, ERRORS DUE TO TIDAL ZONING CAN EASILY EXCEED 0.20 METER (95% CONFIDENCE LEVEL)

  16. TIDAL ZONING EERRORS CAN DOMINATE THE ERROR BUDGET IN AREAS OF COMPLEX AND ILL-DEFINED TIDAL REGIMES AND IN AREAS WHICH METEROROLGICAL FORCING DOMINATES THE TIDE. IN THESE SITUATIONS, ERRORS DUE TO TIDAL ZONING CAN EASILY EXCEED 0.20 METER (95% CONFIDENCE LEVEL)

  17. Tides and Water Level Requirements For Hydrographic Surveys FUNCTIONAL AREAS – NOS/CONTRACT SURVEYS NOS Responsibility 1. Tide and Water Level Requirement Planning 2. Preliminary Tidal Zoning Development 3a. Control Water Level Station Operation NOS or Contractor Responsibility 3b. Supplemental Water Level Station Installation, operation and removal 4. Data Quality Control, Processing and Tabulation 5. Tidal Datum Computation and Tidal Datum Recovery 6. Generation of Water Level Reducers and Final Tidal Zoning

  18. Request for Tides / Water Level Support

  19. Request for Tidal Zoning Correctors

  20. 1. Tide and Water Level Requirement Planning

  21. 2. Preliminary Tidal Zoning Development

  22. 3a. Control Water Level Station Operation

  23. 3a. Control Water Level Station Operation • The control station must be in operation during the entire survey • period if used for direct control. • Must be in operation for the entire time period a subordinate station • is in operation for datum determination of the subordinate and for • gap filling if necessary • Control stations are usually operated by other groups than the • survey parties or field teams. The operational leads of the parties • or teams must ensure operation of the control stations by linking to • the data sources and maintaining communication with the control • station operating unit. • Program planning must include designating alternate control station • scenarios.

  24. Tides and Water Level Requirements For Hydrographic Surveys FUNCTIONAL AREAS – NOS/CONTRACT SURVEYS NOS Responsibility 1. Tide and Water Level Requirement Planning 2. Preliminary Tidal Zoning Development 3a. Control Water Level Station Operation NOS or Contractor Responsibility 3b. Supplemental Water Level Station Installation, Operation and removal 4. Data Quality Control, Processing and Tabulation 5. Tidal Datum Computation and Tidal Datum Recovery 6. Generation of Water Level Reducers and Final Tidal Zoning

  25. 3b. Supplemental Water Level Station Installation, Operation and removal

  26. Wind Wind Influence Great example for not running hydro of predicted tides!

  27. Rain Influence • Rain / River Runoff can distort tidal signatures • Run hydrography during anomalous period- significant error in tide reducers.

  28. Dover

  29. Diurnal / Semidiurnal Transitional Areas Gulf of Mexico 5.6 miles Atlantic Ocean

  30. Key Colony Vaca Key CHANGE IN TIDE TYPE High range Semi-diurnal tide Low range Noisy diurnal tide

  31. Geology Changing Areas

  32. Hydrography in this area could be significantly affected by the change in topography

  33. Shallow Areas

  34. NWLON Stations and Active Stations http://www.tidesandcurrents.noaa.gov/gmap3/

  35. 4. Data Quality Control of Subordinate Stations

  36. 4. Data Quality Control, Processing and Tabulation

  37. 5. Tidal Datum Computation and Tidal Datum Recovery

  38. 6. Generation of Water Level Reducers and Final Tidal Zoning • Water level reducers are time series of observed or final “zoned” • data corrected to the appropriate tide station observations • for the time period of the soundings and are relative to MLLW. • In post-processing mode, the reducers and final zoning must await • final level close-outs, data processing, datum determination, and • generation of final tide reducers after the survey period is over. • For an In-Survey processing mode, data are being collected from • the control and/or subordinate stations routinely or in near-real time • and applied relative to MLLW shortly after sounding collection • if the tide station has a verified MLLW datum prior to the survey. • In this mode, the zoning must be well established “final” zoning • that would expect to change with new measurements. • Final Quality assurance must be done on all data and meta-data • records regardless of the operational mode.

  39. TIDAL ZONING IS THE EXTRAPOLATION OF AND/OR INTERPOLATION OF TIDAL CHARACTERISTICS FROM A KNOWN TIDE STATION(S) TO A DESIRED SURVEY AREA USING CORRECTORS IN THE FORM OF TIME DIFFERENCES AND RANGE RATIOSPRELIMINARY TIDAL ZONING IS FOR SURVEY PLANNING AND FOR OPERATIONS WHEN THE SYRVEY IS IN POSTPROCESSING MODE. CORRECTORS ARE APPLIED TO THE CONTROL STATION OF A NOAA TIDE PREDICTION REFERENCE STATION FINAL TIDAL ZONING CORRECTORS ARE APPLIED TO THE OBSERVATIONS DURING THE SURVEY PERIOD FROM APPROPRIATE SUBORDINATE OR(AND) CONTROL STATIONS AS SPECIFIED IN THE PROJECT INSTRUCTIONSTHE GEOGRAPHIC STRUCTURE OF THE DISCRETE TIDE ZONING IS LARGELY BASED ON THE LOCATION OF THE ESIMATED CO-TIDAL LINES. THIS STRUCTURE CHANGES ONLY WHEN NEW INFORMATION IS OBTAINED FROM NEW SUBORDINATE STATIONS THAT IMPROVES THE ACCURACY AND RESOLUTION OF THE EXISTING ZONING Discrete Tidal Zoning

  40. 6. Generation of Water Level Reducers and Final Tidal Zoning

  41. TIDAL ZONING IS THE EXTRAPOLATION OF AND/OR INTERPOLATION OF TIDAL CHARACTERISTICS FROM A KNOWN SHORE POINT(S) TO A DESIRED SURVEY AREA USING TIME DIFFERENCES AND RANGE RATIOS