Hydrographic Surveys and Oceanography
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Questions and Answers

What is the method of determining the effective capacity of a body of water that requires a moderate degree of precision?

  • Intersecting Range Lines
  • Cross-section Method (correct)
  • Velocity-Area Method
  • Contour Method

    • What is the formula for stream discharge?

  • Q = AV (correct)
  • Q = 2AV
  • Q = A^2V
  • Q = A/V

    • What is the point on the celestial sphere directly beneath the observer?

  • Celestial Axis
  • Zenith
  • Nadir (correct)
  • Celestial Pole

    • What is the great circle of the celestial sphere where a plane, perpendicular to the plumb line at the place of observation and passing through the center of the earth, cuts the celestial sphere?

    <p>Observer's Horizon</p> Signup and view all the answers

    What is the prolongation of the earth's polar axis?

    <p>Celestial Axis</p> Signup and view all the answers

    What is the method of locating sounding used where the boat proceeds to the intersection of any two range lines and soundings are taken?

    <p>Intersecting Range Lines</p> Signup and view all the answers

    What is the formula for the area in each section using the Velocity-Area Method?

    <p>a = ½ (b1+b2) h</p> Signup and view all the answers

    What is the vertical line at the location of the observer which coincides with the plumb line and is normal to the observer's horizon?

    <p>Observer's Vertical</p> Signup and view all the answers

    What is the primary purpose of hydrographic surveys?

    <p>To gather information about a body of water and its adjacent land areas</p> Signup and view all the answers

    What is the term for the average height of the sea for all stages of the tide?

    <p>Mean Sea Level</p> Signup and view all the answers

    What is the process of measuring the depth of a body of water at a particular point?

    <p>Soundings</p> Signup and view all the answers

    What is the term for the half-daily cycle of rhythmic rise and fall of the surface of oceans, seas, lakes, bays, rivers, and other bodies of water?

    <p>Tide</p> Signup and view all the answers

    What is the term for an echo-sounding equipment that produces, transmits, and receives the sound waves, then calculates the depth based on the time interval of the echo's return?

    <p>Fathometer</p> Signup and view all the answers

    What is the term for the process of selecting the most suitable manner of executing a survey?

    <p>Reconnaissance</p> Signup and view all the answers

    What is the term for the remote sensing method that uses light in the form of a pulsed laser to measure ranges/distances to the Earth?

    <p>LIDAR</p> Signup and view all the answers

    What is the term for the method of finding the coordinates of a point in a body of water using three known control points?

    <p>Three Point Resection</p> Signup and view all the answers

    Study Notes

    Hydrographic Surveys

    • Hydrography is the process of gathering information about bodies of water and adjacent land areas.

    Preliminary Steps

    • Reconnaissance is a preliminary step in selecting the most suitable manner of executing a survey.

    Tides and Water Levels

    • A tide is the daily cycle of rhythmic rise and fall of the surface of oceans, seas, lakes, and other bodies of water due to gravitational attraction.
    • Mean Sea Level is the average height of the sea for all stages of the tide.

    Measuring Water Depth

    • Soundings involve measuring the depth of a body of water at a particular point.
    • Echo Sounding measures water depth by sending high-frequency sound waves to the water bed and timing their return.
    • A Fathometer is an echo-sounding equipment that produces, transmits, and receives sound waves, calculating depth based on the time interval of the echo's return.

    Positioning and Mapping

    • An Electronic Positioning System uses unmodulated radio waves to determine distance between a ship and ground stations based on travel time of the waves.
    • LIDAR (Light Detection and Ranging) is a remote sensing method that uses light to measure ranges/distances to the Earth.

    Water Management

    • Dredging is the process of widening, enlarging, cleaning, or deepening of channels in harbors, rivers, and canals.
    • Dams are barriers built to hold back or impound water.

    Surveying Methods

    • Three Point Resection is a method to find the coordinates of a point in a body of water using three known control points.
    • Stream Velocity is the speed of water flow in a channel.
    • The Cross-section Method is used to determine the effective capacity of a body of water when a moderate degree of precision is required.
    • The Contour Method is used to establish a reference base line or shore traverse to locate the water line and desired shore topography.

    Formulas

    • Stream discharge: Q = AV
    • Area in each section using Velocity-Area Method: a = ½ (b1+b2) h

    Locating Soundings

    • Intersecting Range Lines is a method of locating soundings where the boat proceeds to the intersection of any two range lines and soundings are taken.

    Astronomical Observations

    Celestial Bodies

    • Celestial Poles are points on the surface of the celestial sphere pierced by the extension of the earth's polar axis.
    • Celestial Axis is the prolongation of the earth's polar axis.
    • Zenith is the point where the plumb line at the place of observation projected above the horizon meets the celestial sphere.
    • Nadir is the point on the celestial sphere directly beneath the observer, opposite to the zenith.

    Observer's Reference Points

    • Observer's Horizon is a great circle of the celestial sphere where a plane, perpendicular to the plumb line at the place of observation and passing through the center of the earth, cuts the celestial sphere.
    • Observer's Vertical is a vertical line at the location of the observer, coinciding with the plumb line and normal to the observer's horizon.

    Celestial References

    • Celestial Equator is a great circle perpendicular to the polar axis of the celestial sphere, an extension of the plane of the earth's equator outward until it intersects the celestial sphere.
    • Vertical Circle is a great circle passing through the observer's zenith and any celestial body, perpendicular to the horizon.

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    Test your knowledge of hydrographic surveys, reconnaissance, and oceanographic concepts such as tides and water bodies.

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