Podcast
Questions and Answers
Which method does NOT include observations entirely from the shore?
Which method does NOT include observations entirely from the shore?
- By two angles from the shore line.
- By transit and stadia.
- Observations from both the shore and the sounding boat. (correct)
- By range and one angle from the shore line.
What is the first step in the location method using transit and stadia?
What is the first step in the location method using transit and stadia?
- Take stadia readings while the boat is stationary.
- Establish a range line and set up a transit on it. (correct)
- Compute distances using tacheometric formulae.
- Row the boat along the range line.
In the field observations, how is the shore divided for taking measurements?
In the field observations, how is the shore divided for taking measurements?
- Through a continuous vertical staff motion.
- Into various range lines at equal intervals. (correct)
- By setting up multiple transits along the shore.
- Into different angles from the shoreline.
Which action is performed while the boatman rows the boat according to the observations by transit and stadia?
Which action is performed while the boatman rows the boat according to the observations by transit and stadia?
What is the purpose of taking stadia readings in the method of locating soundings?
What is the purpose of taking stadia readings in the method of locating soundings?
What is the primary purpose of setting up the transit near the water level?
What is the primary purpose of setting up the transit near the water level?
Which of the following is true about the method of taking observations with the boat?
Which of the following is true about the method of taking observations with the boat?
What action should the signal man take just before sounding?
What action should the signal man take just before sounding?
In what scenario is the location by two angles method preferable?
In what scenario is the location by two angles method preferable?
What should the transit man do at the instant of sounding?
What should the transit man do at the instant of sounding?
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Study Notes
Learning Objectives
- Students will gain knowledge on methods used for locating soundings.
- Focus areas include observations from the shore, from a sounding boat, and using both.
Methods of Locating Soundings
- Three primary observation methods: from the shore, the sounding boat, and a combination of both.
Observations Entirely from the Shore
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By Transit and Stadia:
- Establish a range line and set up a transit.
- Hold a leveling staff vertically and row the boat along the range line.
- Take stadia readings and compute distances with tacheometric formulae.
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Range and One Angle from the Shore:
- Set multiple range lines and place the transit perpendicular to a chosen range.
- Row the boat along the range line, with signal coordination for angle recording.
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By Two Angles from the Shore:
- Requires two transits at visible points for angle measurement.
- Observers note angles simultaneously when a signal is given from the boat.
- Calculations involve using the sine rule for triangulation.
Observations Entirely from the Sounding Boat
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Range and One Angle from the Boat:
- Set up range lines and fix a signal at the end of one line.
- Measure angles at the moment of soundings and record the time.
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Two Angles from the Boat:
- Measure angles simultaneously from known points on shore using a sextant.
- Calculate coordinates based on previously noted angles.
Observations from Both Shore and Boat
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Range and Time Interval:
- Set up range lines and note the time of soundings taken at uniform velocity.
- Distances can be calculated using the boat's speed and timing between soundings.
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Intersecting Ranges:
- Permanent marking of range lines aids in tracking changes in the water body’s bottom.
- Repeated soundings are taken at intersection points of range lines.
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Distances along a Stretched Wire Across a River:
- A wire between two banks is marked for measuring distances to reference points on shore.
- Soundings taken under each tagged point; this method is highly accurate but costly.
Key Considerations
- Method suitability varies with water depth and conditions; some are only applicable to shallow, smooth waters.
- Precision of observations is dependent on the setup of instruments and conditions during measurement.
- Timing and proper coordination are critical in ensuring accuracy in soundings.
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