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branch of survey that deals with water bodies
Hydrography
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study, description and mapping of ocean, lakes and rivers
Hydrography
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process of measuring depth of body of water
Sounding
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unit measurement of water
Fathom
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1 fathom= ?
6ft
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process of making measurements to predict water rate of discharge
Stream Gauging
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a map or chart of water
Hydrographic Chart
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specific tide levels used as surface of reference for depth measurement
Tidal Datum
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volume of water flowing past a section of waterways
Discharge
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current or steady flow of water
Stream
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process of scooping and sucking up mud
Dredging
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imaginary line found on the surface of the Earth underwater
Subaqueous Contour
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Steps in Hydrography
Reconnaissance, Establishment of Horizontal Control, Establishment of Vertical Control, Topographic Survey, Hydrography, Preparation of Hydrographic Map
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Equipments Used In Hydrographic Surveying
Sextant, Sounding Craft, Sounding Machine, Sounding Pole, Leadline, Fathometer, Signal, Tide Gauge
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Rise and Fall of sea level cause by gravitational forces exerted by moon and sun
Tides
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Moon and Earth
Lunar Tide
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Sun and Earth
Solar Tide
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High Tide Above Average, Low Tide Below Average
Spring Tide
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Low Tide Above, High Tide Below
Neap Tide
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water is falling and moving seaward
Ebb Tide
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water surface rising and moving toward shore
Flood Tide
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Horizontal Movement of Water
Tidal Current
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direction of current flow
Set
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speed of current flow
Drift
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period which the greatest peak or depression was reached
Stand
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Principal Datum Used
Mean Sea Level, Mean Low Water, Mean Lower Low Water, Mean Low Water Spring
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two high and two low tides each tidal day
Semidiurnal Tide
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one high and one low tide
Diurnal Tide
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two high and two low each day
Mixed Tide
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Types of Tide Gauges
Registering, Non Registering
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Simplest Type of Gauge
Staff Gauge
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Consisted of graduated board
Staff Gauge
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used when intensity of tide is high and more variation of water level
Float Gauge
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consist a weight attached to a brass or wire
Weight Gauge
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automatically record the variation of water level within time
Self Registering Gauge
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obtained by taking the mean of height of all tides measured at a regular interval of one hour over a stated period
Mean Sea Level
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Composition of Sounding Party
Chief of Party, Instrument Man, Recorder, Leads Man, Coxswain, Lookout, Signal Man, Fathometer Attendant
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line along which sounding are made
Range Line
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required to mark range line
Shore Signal
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Range Line = _ Signals
2
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a float made of light wood or hollow air tight vessel
Buoy
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Index Glass, Index Arm, Horizon Glass, Pin Hole Plate, Ring Carrying Telescope, Arc, Vernier, Clamp, Tangent Screw, Reading Glass, Handle
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a hand driven machine consist of cast iron casing
Weddell's Sounding Machine
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measure the depth below the boat on which it is installed
Echo Sounding Machine
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Most Common Angle Measureming Instrument
Theodolite, Prismatic Compass, Sextant
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used in measuring angle from sounding boat
Sextant
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observation are made from the shore
Prismatic Compass and Theodolite
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instant at which the tidal current direction and flows neither in or out
Slack Water
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consist of large head or front of water generated at the surface of the ocean
Tidal Waves
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Different Methods of Locating Sounding
Time Interval Along Range Line, Range Line and An Angle From Shore, Intersecting Range Line, One Angle and Stadia Distance From Shore, Two Angles From Shore, Two Angles From Boat, Distance Along Cross Rope or Wire, Direction or Vertical Angle
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simple device in which piano or stranded wire is used and wound on a reel mounted on a stand
Sounding Machine
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usually a length of sash or hemp cord, braided flax, or nylon cord,
Leadline
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graduated and rounded piece of lumber, about 3 meters long, used for taking soundings.
Sounding Pole