This document summarizes key aspects of hydrographic surveying. It discusses measuring water depths through sounding, establishing horizontal and vertical controls, surveying shorelines, instruments used for sounding like sounding poles and echo sounders, reduction of soundings to a datum, teams involved in surveys, cartography methods to prepare nautical charts, key elements of nautical charts including datums and symbols, and common terms used in hydrography.

1. Hydrographic SurveyIldefonso, Sorbi

2. HydrographyBranch of science that deals with the measurement of bodies of water

3. Deals with the physical features of the navigable portion of the earth’s surface and adjoining coastal areas.

4. Sounding –measurement of depth below the water surface

5. Applications of sounding:

6. Making nautical charts for safety of navigation

7. Development and engineering projects such as piers, dams and bridges

8. Scientific and academic studiesHorizontal Control and Vertical ControlHorizontal Control

9. For large areas – 2nd or 3rd order triangulation

10. For smaller areas – transit-tape traverse

11. For small detached areas – stadia, graphical, plane table methods

12. For long narrow river – traverse on one side

13. For width >1km – traverse on both sides

14. Vertical Control

15. Tide gauges are used to establish the common datum before sounding is takenShoreline SurveyShoreline

16. Syn. to Coastline

17. Line of contact between the land and the body of water

18. USC&GS uses the high water line

19. It consist of:

20. Determination or delineation of shorelines

21. Location of shore details and prominent features to which soundings may be connected

22. Determination of low and high water linesMethods of Locating SoundingFrom the shore

23. Location by Cross-Rope

24. Location by two angles from the shore

25. Location by Range and One angle from the shore

26. From the boat

27. Location by two angle from the boat

28. Location by Range and One angle from the boat

29. From both the shore and the boat

30. Location by One angle from the shore and from the boat

31. Location by Range and Time Intervals of the boat

32. Location by Intersecting Ranges

33. Location by Tacheometric ObservationsSounding LinesSystems of Sounding Lines

34. Parallel straight lines –> open coasts

35. Radiating lines –> small bays and islets

36. Circular curves or arcs –> isolated shoal

37. Spacing of Sounding Lines

38. Factors: the scale of the survey, depth of water, proximity to shore, character of submarine relief, importance of the regionInstruments used in SoundingThe methods of determining water depth are differentiated by the instruments used .

39. Sounding Pole

40. The Leadline

41. Sounding Machines

42. Registering sheaves

43. Echo sounding Instrument or FathometerEcho SoundingDistance is measured by multiplying half the time(t) from the signal's outgoing pulse to its return by the speed of sound(S) in the water, which is approximately 1.5 kilometres per second.D=0.5(t)*SIt takes in to account the factors of temperature, pressure and salinity to calculate the actual sound speed.

44. Reduction of SoundingThe reduced sounding are the reduced levels of the submarine surface in terms of the adopted datumA correction equal to the difference of level between the actual water level(gauge reading) and the datum(MLW/MLLW) is applied to the observed soundings.

45. Hydrographic Survey TeamOfficer-in-charge/Chief-of-partyLeft AnglemanRight AnglemanRecorderFathometer attendantLeadsmanLeadsman’s assistantHelmsman or CoxwainEngineerAdditional general utility personnel

46. Hydrography and CartographyCartography – science and art of the production of maps and charts

47. Nautical charts-> polyconic projection

48. Instruments used in the preparation of Nautical Charts

49. 3-arm protractor

50. Hairspring divider

51. Spacing divider

52. Proportional divider

53. Meter Bar

54. Opisometer/Map measure

55. Beam CompassThe Nautical ChartA nautical chart is a graphic representation of a maritime area and adjacent coastal regions.

56. Datums of a Nautical Chart

57. Horizontal Datum

58. Vertical Datum

59. Atlantic Ocean – Mean Low Water

60. Pacific Ocean – Mean Lower Low WaterNautical ChartThe Nautical chart or hydrographic map should contain the following information

61. Datum used

62. High, mean, low water lines

63. Soundings

64. Line of equal interpolated from the soundings called depth curves

65. Conventional symbols

66. All safety devices such as lighthouse, buoys etc.

67. Complete border informationPlotting of SoundingsSoundings can be plotted in 3 ways

68. Mechanical Solution

69. By tracing paper

70. By Station Pointer

71. Graphical Solution

72. Method 1

73. Method 2

74. Analytical SolutionOther Essential in HydrographyThe SextantAn instrument used to measure the angle between any two visible objects. The Boat sheet/Hydrographic sheetThe Wire dragA device used to detect obstructions such as boulders and ledges. These obstructions should be plotted in the Navigational charts.

75. Common Terms used in HydrographyMarginal continental featuresBankContinental shelfContinental slopeInsular shelfInsular slopeDeep Sea Depression & Deep Sea ElevationsBasinDeepDepressionDepthForedeepTrenchPlateaduRidgeSeamountSwell

76. Common Terms used in HydrographyEmbaymentsBayBrightCoveHarborInletGulfCoastal FeaturesCapeCoastHigh-water LineIslandIsletLow-water linePoint

77. Common Terms used in HydrographyStreamsBayouBrook and RunCreekLagoonRiverSloughCaldronCanyonSeavalleyValleySubmarine ElevationsBankCrestDome KnollLedgePinnacleReefShoalSpur