Plane Table Surveying Techniques
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Plane Table Surveying Techniques

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Questions and Answers

What is the first step in setting out the table?

  • Levelling (correct)
  • Adjusting the tripod
  • Orientation
  • Centring

    • What is the purpose of centring the table?

  • To align the table with the magnetic north
  • To place the table directly over the station on the ground (correct)
  • To adjust the alidade for accurate sighting
  • To ensure the table is level

    • Which of the following methods of orientation is described as fast but less accurate?

  • Orientation by alidade
  • Orientation by trough compass (correct)
  • Orientation by leveling
  • Orientation by back sighting

    • Which component is used for centring the table?

    <p>Plumbing fork</p> Signup and view all the answers

    What is the main goal of orientation when using multiple instrument stations?

    <p>To avoid distortion of the map</p> Signup and view all the answers

    In orientation by back sighting, what is drawn towards the next station?

    <p>A line from station A to station B</p> Signup and view all the answers

    What is crucial for maintaining consistency in orientation at different stations?

    <p>Sighting along the same lines</p> Signup and view all the answers

    What happens if the orientation is not properly executed?

    <p>There will be distortion in the map</p> Signup and view all the answers

    What is one of the main purposes of the radiation method in plane table surveying?

    <p>To locate details based on triangulation from a point</p> Signup and view all the answers

    Which component of the transit theodolite is primarily used for measuring vertical angles?

    <p>The vertical circle</p> Signup and view all the answers

    In tacheometric surveying, what role does the stadia rod play?

    <p>It is used to calculate distances based on sight distance</p> Signup and view all the answers

    What is indicated by checking for closing errors in open traverse surveying?

    <p>The difference between intended and actual closing point</p> Signup and view all the answers

    Which of the following methods involves measuring distances at intervals using a leveling instrument?

    <p>Stadia method</p> Signup and view all the answers

    What is the function of the anallatic lens in tacheometric surveying?

    <p>To enable distance measurement without the need for a stadia rod</p> Signup and view all the answers

    What technique is used to measure both interior and exterior angles in theodolite surveying?

    <p>The included angle method</p> Signup and view all the answers

    Which surveying technique is primarily used for leveling over short distances?

    <p>Theodolite surveying</p> Signup and view all the answers

    What is the first step in leveling with a three-foot screw?

    <p>Place the plate level parallel to a line joining two diagonally opposite levelling screws.</p> Signup and view all the answers

    When should the instrument be rotated by 180 degrees during the leveling process?

    <p>If the bubble is still not centered after adjustments.</p> Signup and view all the answers

    What is parallax and how can it be eliminated?

    <p>It occurs when the image doesn't lie in the plane of the crosshair, eliminated by focusing the eyepiece and objective.</p> Signup and view all the answers

    What adjustment is necessary if the bubble does not remain centered after the 180-degree rotation?

    <p>Permanent adjustment of the instrument is needed.</p> Signup and view all the answers

    What is the correct procedure to measure a horizontal angle with a transit theodolite?

    <p>Set up the theodolite, level it, and then adjust the vertical circle.</p> Signup and view all the answers

    Which action is performed after keeping the vertical circle at left during the angle measurement?

    <p>Rotate the upper plate until the vernier coincides with the main scale.</p> Signup and view all the answers

    What do you need to do if the image through the telescope is not clear?

    <p>Focusing of both the eyepiece and the objective is required.</p> Signup and view all the answers

    In the leveling process, what is the purpose of rotating screws B&D?

    <p>To bring the bubble of the plate level to the center.</p> Signup and view all the answers

    What is the least count of the vernier scale described?

    <p>20&quot;</p> Signup and view all the answers

    Which reading needs to be taken first when using the vernier scale?

    <p>Main scale reading in degrees and minutes</p> Signup and view all the answers

    What is the process of centering the instrument on the station?

    <p>Moving the tripod while ensuring the plumb-bob touches the ground point</p> Signup and view all the answers

    What measurement must be combined with the vernier reading for the final observation?

    <p>Both main scale reading and least count of the vernier</p> Signup and view all the answers

    Which method is NOT a part of the temporary adjustments of the theodolite?

    <p>Calibration adjustment</p> Signup and view all the answers

    What tool is used for accurate levelling of the theodolite?

    <p>Foot screws and plate level</p> Signup and view all the answers

    What is the purpose of leveling the theodolite at the starting point A?

    <p>To ensure the instrument is stable and aligned</p> Signup and view all the answers

    What distinguishes a closed traverse from an open traverse?

    <p>A closed traverse returns to the starting point</p> Signup and view all the answers

    What indicates that the theodolite is properly levelled?

    <p>The bubble remains centered after a 180-degree rotation</p> Signup and view all the answers

    What should be done if the bubble does not remain centered during the levelling process?

    <p>Proceed with permanent adjustment</p> Signup and view all the answers

    Which method is preferred for measuring angles in theodolite traversing?

    <p>Taking readings of both verniers and using face observations</p> Signup and view all the answers

    In the traversing by included angles, which angle measurement can be classified as an exterior angle?

    <p>The angle measured clockwise in a clockwise direction of progress</p> Signup and view all the answers

    What method would be suitable for surveying roads and pipelines with small deflection angles?

    <p>Traversing by deflection angles</p> Signup and view all the answers

    When measuring an interior angle, how is it determined in relation to the direction of progress?

    <p>If the survey progresses anticlockwise</p> Signup and view all the answers

    Which tool is NOT used for measuring lengths in traversing?

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

    What is the primary use of a closed traverse in surveying?

    <p>To locate the boundaries of natural features</p> Signup and view all the answers

    Study Notes

    Plane Table Surveying

    • Plane table surveying uses a plane table, alidade, and plumbing fork to create maps.
    • The alidade is used to sight points and draw lines on the plane table.
    • The plumbing fork is used to center the plane table over a ground station.
    • There are three main methods for plane table surveying: radiation, intersection, and traversing.

    Orientation

    • Orientation ensures the plane table is aligned parallel to itself at different stations to prevent map distortion.
    • Orientation by trough compass uses a compass to align the table with magnetic north. This is fast but less accurate.
    • Orientation by back sighting involves aligning the alidade to a previously sighted point and rotating the plane table until the line of sight passes through the point.

    Theodolite Surveying

    • A theodolite is a surveying instrument used for measuring horizontal and vertical angles.
    • It consists of a telescope, vertical circle, horizontal circle, and levelling screws.
    • Theodolite adjustments include setting on the station, levelling up, and removing parallax.

    Levelling the Theodolite

    • Levelling the theodolite ensures that the instrument is horizontal.
    • Three levelling screws are adjusted in pairs until the bubble of the plate level is centered.
    • Four levelling screws are adjusted in pairs along opposite diagonals until the bubble is centered.

    Measuring Angles

    • Direct method involves pointing the telescope at a target and reading the angle on the horizontal circle - the angle is set to 0 degrees before sighting the first target.
    • Deflection angle method measures the angle between a line and a reference line. The reference line is usually the previous line in the traverse.
    • Magnetic bearing method uses a compass to determine the magnetic bearing of a line. The magnetic bearing is the angle between the line and magnetic north.

    Theodolite Traversing

    • Traversing is a surveying method used to determine the location of points by measuring angles and distances.
    • A traverse is closed if it returns to the starting point and open if it ends at a different point.
    • Traversing with included angles involves measuring the angle between each pair of lines forming the traverse.
    • Traversing with deflection angles involves measuring the angle between each line and the previous line.

    Measuring Angles

    • Direct method involves pointing the telescope at a target and reading the angle on the horizontal circle - the angle is set to 0 degrees before sighting the first target.
    • Deflection angle method measures the angle between a line and a reference line, usually the previous line in the traverse.
    • Magnetic bearing method uses a compass to determine the magnetic bearing of a line, which is the angle between the line and magnetic north.

    Theodolite Traversing

    • Traversing is a surveying method used to determine the location of points by measuring angles and distances.
    • A traverse is closed if it returns to the starting point and open if it ends at a different point.
    • Traversing with included angles involves measuring the angle between each pair of lines forming the traverse.
    • Traversing with deflection angles involves measuring the angle between each line and the previous line.

    Tacheometric Surveying

    • Tacheometric surveying uses a tacheometer to determine distances and elevations of points.
    • A tacheometer is typically a theodolite with a stadia diaphragm.
    • The stadia method uses the stadia diaphragm and a stadia rod to measure the distance between the instrument and the target.

    Stadia Diaphragm

    • The stadia diaphragm contains two horizontal lines that create a stadia interval.
    • The stadia interval is used to calculate the distance between the instrument and the target.
    • The stadia rod is a graduated rod that is held vertically at the target.
    • The distance is calculated using the formula: distance = k * stadia interval + c, where k and c are constants.

    Anallatic Telescope

    • Anallatic telescopes are used in tacheometric surveying to eliminate the constant (c) in the distance formula.
    • With an anallatic telescope, the distance is simply calculated by multiplying the stadia interval by the constant (k).
    • Anallatic lenses are incorporated into the telescope to achieve this.

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    Description

    Explore the essential methods and tools used in plane table surveying, including the alidade, plumbing fork, and various orientation techniques. This quiz also covers the differences between plane table and theodolite surveying, providing a comprehensive overview of these surveying methods.

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