Hydrographic Surveying:

Transcription

1 Hydrographic Surveying: Specifications & Standards IHO USACE NOAA Captain Bob Pawlowski, NOAA (Ret), MNI

2 History of Hydrography 13 th century first known chart Does not include Asia China and Japan 15 th century portolans for sailing Mediterranean to England 16 th century sailing by caping the ship & Dutch Mirrors of the Sea 17 th century Mapping of the British Coast First school of Hydrography in Dieppe France First National Hydrographic Office 18 th century Invention of station pointer (three armed protractor) 19 th century Survey of the Coast for the United States 20 th Century Century of Technology Acoustics, Radio navigation, computers, precise positioning

3 Charting Technology Leadline and Visual shore signals Wire Drag survey First fathometers and Radio Acoustic Ranging Automatic Recording Fathometer Shoran (Radar positioning system) Long and Medium range Hyperbolic positioning systems Digital data collection 1970s - Narrow Beam Fathometer & Side scan sonar 1980s - Dual Beam Fathometer Multi-Beam Sounding System 1990s - Global Positioning System Shallow Water Multi-Beam System Digital Terrain Modeling (quality control & visualization) Integrated sensor technology

4 Sea Floor Coverage by Survey Instrument Single Beam Sidescan Multibeam Continuous Line of Depth Points Continuous swath of detailed imagery Continuous Array of Depth Points and Imagery

5 Standards of Performance IHO M-13 USACE Hydrographic Surveying Engineering Manual NOAA Specifications and Deliverables Survey Standards Horizontal Control NGS & GPS Vertical Control Co-Ops Manuals Professional Papers & Associations Hydro Magazine & Hydro Conference IHO & THSOA

6 IHO M-13 Table of Contents CHAPTER 1: PRINCIPLES OF HYDROGRAPHIC SURVEYING CHAPTER 2: POSITIONING CHAPTER 3: DEPTH DETERMINATION CHAPTER 4: SEAFLOOR CLASSIFICATION AND FEATURE DETECTION CHAPTER 5: WATER LEVELS AND FLOW CHAPTER 6: TOPOGRAPHIC SURVEYING CHAPTER 7: HYDROGRAPHIC PRACTICE

7 Orders of Surveys IHO Orders Special Order scale First Order accuracy Second Order Third Order Minimum standards in Table 1.1

8 Horizontal Accuracy - Radius IHO Standards : Special Order - First Order - Second Order - Third Order - 2 meters 5 meters + 5% of depth 20 meters + 5% of depth 150 meters + 5% of depth DGPS is First Order Survey Accuracy

9 Sounding standards equation Vertical Accuracy Relative to depth ± 2 [ a + ( b* d ) 2 Special Order: a=0.25, b=.0075 and d=depth 1 st Order: a = 0.5, b = and d = depth. 2 nd & 3 rd Order : a=1.0, b =0.023 and d=depth

10 Bottom Coverage Special Order 100% compulsory cubic resolution >1 m First Order 100% in selected areas (navigation channels) cubic resolution >2 m to 40 m, 10% depth beyond 40 m line spacing 3 x water depth or 25 m, whichever is greater Second Order 100% may be required in selected areas cubic resolution >2 m to 40 m, 10% depth beyond 40 m line spacing 3-4 x water depth or 200 m, whichever is greater Third Order Not applicable for coverage or cubic resolution Line spacing 4 x average water depth

11 Zone of Confidence A1: Modern Survey +/- 5 m &.05m +1% d : full survey achieved A2: Complete Survey +/-20m & 1.0m + 2% d : full survey achieved B: Incomplete Survey +/-50m & 1.0m + 2% d : systematic C: Incomplete survey +/-500m & 2.0m + 5% d : low accuracy survey D: Worse than C Poor data or information can not be assessed U: Unassessed Table 1.2. Categories of Zone of Confidence in Data ZOC Table

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13 Perspective of survey data in Alaska 60% of nations critical survey needs in Alaska Huge area marginally surveyed Change with geologic activity Earthquakes Volcanoes Glaciers Coastal Erosion and Deposition Changing coastal commerce Fishing Mineral Exploration, Development and Shipping Oil & Gas Development and Maintenance Tourism Critical Habitat designation

14 Sonar Equation Echo detection depends on the factors of the Sonar Equation: EE = SL 2TL-(NL-DI)+BS-DT EE is Echo Excess SL is Source Level TL is Transmission Loss (2x for down and back) NL is Noise Level DI is Directivity Index BS is Back Scatter DT is Detection Threshold

15 Sound Velocity & Depth Sound Velocity Sounding to and from Determined by temperature and salinity Impacted by thermoclines and pycnoclines Formula: D = V * T + K + D r 2 Where V = sound velocity; T=time, K=system constant, & D r = transducer depth Example Sampling depths of instruments on 1000 m

16 Sound Velocity C (Z, T, S) = T[ T( T)] + (3. 17) + [ T( T)](S - 35) + Δ(Z) 16.3 Z Z 2 C = sound speed (m/s) T = temperature ( o c) S = salinity (psu) Z = depth (m) As presented by Coppens [Kinsler et al., 1982]:

17 Ellipsoid The three-dimensional shape obtained by rotating an ellipse about its minor axis The major and minor axes are not the same Many people use the terms Spheroid and Ellipsoid interchangeably.

18 The Geoid Earth-Shaped, gravity based Results from Flattening at the poles and bulging a the equator Bulges and depressions irregularly located around the Earth Critical for large-scale mapping and is the reference surface for groundsurveyed horizontal and vertical positions Models of the geoid referenced to an ellipsoid

19 Alaska Geoid Geoid-forming data are gravity based using gravimeters Improved on by vertical bench mark leveling Neither dataset is adequately populated in Alaska Causes gaps in the modeling NGS Geoid99 is the most recent for the state Has errors of up to 2 meters Geoid99 Alaska

20 Ellipsoid Heights and Tide Datums Ellipsoid Heights now being required on Tidal Benchmarks Relationship of Ellipsoid Heights to Tide Datums EH more stable Used for Aircraft positioning (LIDAR, photogrammetry) Repeatable Separation is not constant NOS/NGS 58 Standards Ref to WGS-84 GEOID99, GEOID2004 Documentation of Results

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22 NOAA NWLON Gauges in Alaska

23 Shoreline change with tectonic activities along the Aleutian and Kodiak Islands ( with specific stations

24 Time Scales Longer cycles of variation also appear in measured tides spring tides (high range) occur every other weak neap tides (low ranges) occur between spring tides

25 Tidal Constituents Complex tidal variations can be modeled by adding the effects of separate waves these separate amplitudes and frequencies define tidal constituents

26 Cotidal Lines, Gulf of Alaska Cotidal lines in Cook Inlet, Alaska give the impression of a wave washing up the inlet Time differences are predictable by the phase speed equation c = gh

27 Corange Lines, Gulf of Alaska In Cook Inlet, ranges on the east side are higher than points directly across, on the west side (along cotidal lines)

28 STATION HIERARCHY TERTIARY PRIMARY TIDE STATION: more minimum than 30 of days 19 but years less than a year SECONDARY allows statistical TIDE and STATION: datum control for short term stations minimum of 1 yr but less than 19 yrs

29 Tide Measurements Long-term statistical analysis of measured water levels results in these statistical levels A tidal epoch of 19- years is required to measure all astronomical variations

30 ELEVATIONS ON STATION DATUM National Ocean Service (NOAA) Station: T.M.: 0 W Name: SELDOVIA, COOK INLET, AK Units: Meters Status: Accepted Epoch: Datum Value Description MHHW Mean Higher-High Water MHW Mean High Water DTL Mean Diurnal Tide Level MTL Mean Tide Level MSL Mean Sea Level MLW Mean Low Water MLLW Mean Lower-Low Water SELDOVIA, COOK INLET (Tide Staff) TIDAL EPOCH: CONTROL TIDE STATION: Elevations of datums referred to MLLW (Mean Lower Low Water) METERS: MHHW = MHW = MSL = MTL = MLW = MLLW = GT Great Diurnal Range MN Mean Range of Tide DHQ Mean Diurnal High Water Inequality DLQ Mean Diurnal Low Water Inequality HWI Greenwich High Water Interval (in Hours) LWI 4.92 Greenwich Low Water Interval (in Hours) NAVD North American Vertical Datum

31 Tide Stations w/ Published Datums NTDE stations NTDE stations

32 Unpublished Tide Stations Lower Cook Inlet

33 Figure Corange Line of Greenwich, High and Low Water Intervals (In Hours)

34 Figure Tidal Zoning for Approaches to Nikiski, Alaska

35 Figure Final Tide Note and Final Tidal Zoning Chart (continued)

36 Topographic Surveying & Shoreline Determination RTK-GPS Horizontal and vertical accuracy Photogrammetry Tide Coordinated Limited in Alaska Satellite Altimetry Inadequate resolution in Western and Northern Alaska

37 USACE Coastal Engineering Surveys

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40 Hydrographic Practice Project Planning Site Characterization Data Assessment Resource Allocation Platform and Technology Data Acquisition Horizontal and Vertical Control Depth determination Accuracy and Quality Control Data Products and Reports As defined by standards

41 ACSM CERTIFICATION Officially recognized by ACSM Does not supersede State Registration/Certification 5 years hydrographic experience 2 years in technical charge 2 years in the field Application & Examination 1000 word essay 2 part examination Internet Information