Linear Measurement Corrections Quiz
57 Questions
2 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What correction is applied to linear measurements to account for the extension of the chain or tape?

  • Standard length correction
  • Temperature correction
  • Pull correction (correct)
  • Sag correction

    • If the field temperature is less than the standardized temperature, what is the nature of error and correction in temperature correction?

  • Error: positive, Correction: zero
  • Error: positive, Correction: negative (correct)
  • Error: negative, Correction: positive
  • Error: zero, Correction: positive

    • In temperature correction, if the coefficient of linear expansion is higher, what happens to the recorded length compared to the actual length?

  • Recorded length is less than actual length (correct)
  • Recorded length is equal to actual length
  • Recorded length is more than actual length
  • No difference in recorded and actual lengths

    • Which correction is made when the difference between pull force and standard pull is considered in linear measurements?

    <p>Pull correction</p> Signup and view all the answers

    What is the nature of error and correction when the pull force is less than the standard pull in pull correction?

    <p>Error: positive, Correction: negative</p> Signup and view all the answers

    In linear measurements, if Young’s modulus of elasticity of the material increases, what happens to the extension of the chain or tape?

    <p>Extension increases</p> Signup and view all the answers

    What is the term used to describe the sag correction in the tape or chain measurement?

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

    Why was triangulation historically preferred for establishing control points?

    <p>It was easier to measure angles than distances</p> Signup and view all the answers

    What type of triangles were primary trig points fixed at in triangulation networks?

    <p>Equilateral triangles</p> Signup and view all the answers

    What was the reduction in observational accuracy when transitioning from primary to secondary triangulation networks?

    <p>-20%</p> Signup and view all the answers

    How were the base lines measured in classical triangulation?

    <p>By invar tapes in catenary</p> Signup and view all the answers

    What does the scale error in triangulation refer to?

    <p>Error resulting from incorrect base line measurement</p> Signup and view all the answers

    Where are control stations typically situated in urban areas for roof-top triangulation?

    <p>On accessible buildings' roofs</p> Signup and view all the answers

    What is the main requirement for conducting successful triangulation in open, hilly country?

    <p>'Long, uninterrupted sight lines'</p> Signup and view all the answers

    What is the purpose of the up-and-down movement of the prism in a prismatic compass?

    <p>To provide an adjustment for focusing</p> Signup and view all the answers

    Why are dark glasses swung in front of the back vane in a prismatic compass?

    <p>To aid in solar observations</p> Signup and view all the answers

    What is the function of the lifting pin and lifting lever in a prismatic compass?

    <p>To lift the magnetic needle out of pivot point</p> Signup and view all the answers

    Why is a mirror located in front of the forward vane in a prismatic compass?

    <p>To assist in solar observations</p> Signup and view all the answers

    Which component of a prismatic compass is used to read graduations on the graduated ring?

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

    What is the purpose of the reflecting mirror in a prismatic compass?

    <p>To get an image of an object located above or below instrument level while bisection</p> Signup and view all the answers

    Why are slightly convex faces used for the 45º reflecting prism within a prismatic compass?

    <p>To magnify the image of the graduations</p> Signup and view all the answers

    What is carried on a mounting that can be moved up and down between slides fixed on the outside of a prismatic compass case?

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

    What is viewed through a small circular aperture in the prism mounting of a prismatic compass?

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

    Why are dark glasses swung in front of the back vane when solar observations are being taken?

    <p>To reduce glare</p> Signup and view all the answers

    What is the method used when the end stations are not visible from intermediate points when a jungle area obstructs the chain line?

    <p>Reciprocal ranging</p> Signup and view all the answers

    In compass survey, how are the directions of survey lines typically measured?

    <p>By using a magnetic compass</p> Signup and view all the answers

    What is a typical example of an obstacle that obstructs chaining but not ranging?

    <p>Water bodies like lakes and rivers</p> Signup and view all the answers

    Which instrument is generally used for the rapid filling of detail in larger surveys and explanatory works?

    <p>Prismatic compass</p> Signup and view all the answers

    What should be ensured to avoid errors when using a compass survey?

    <p>Presence of magnetic disturbances</p> Signup and view all the answers

    What type of survey is preferred when the area to be surveyed is small but a high degree of accuracy is desired?

    <p>Chain survey</p> Signup and view all the answers

    What is the main function of ensuring the best positions for survey stations?

    <p>Economy of observation</p> Signup and view all the answers

    Why are braced quadrilaterals considered advantageous in surveying?

    <p>They provide more conditions of adjustment</p> Signup and view all the answers

    In triangulation, what method would inevitably be used?

    <p>Method of directions</p> Signup and view all the answers

    What is essential for a target used in surveying?

    <p>Capable of being accurately centered over the survey point</p> Signup and view all the answers

    What should be done if there are angles less than 25°?

    <p>Ensure they are situated opposite a side not entering into scale computation</p> Signup and view all the answers

    What should be done to ensure ground is satisfactory for long-term survey stations construction?

    <p>Study soil conditions</p> Signup and view all the answers

    Why might signal lamps be used as targets in highly precise networks?

    <p>They are suitable for night observations</p> Signup and view all the answers

    What is the purpose of the spring brake or brake pin when using a prismatic compass?

    <p>To dampen the oscillation of the needle</p> Signup and view all the answers

    How is centering checked when using a prismatic compass?

    <p>By adjusting the legs of the tripod</p> Signup and view all the answers

    What is the aim of leveling the compass in surveying?

    <p>To freely swing the graduated circular ring</p> Signup and view all the answers

    How can focusing be achieved when using a prismatic compass?

    <p>By moving the prism up or down</p> Signup and view all the answers

    What causes the largest variation in magnetic declination?

    <p>Secular Variation</p> Signup and view all the answers

    What does diurnal variation refer to in terms of magnetic declination?

    <p>A swing of the compass needle about its mean daily position</p> Signup and view all the answers

    What is a magnetic bearing in surveying?

    <p>The angle between magnetic meridian and survey line direction</p> Signup and view all the answers

    How does a magnetic meridian differ from a true meridian?

    <p>Magnetic meridians follow earth's magnetic field, true meridians do not</p> Signup and view all the answers

    What characteristic defines a surveyor's compass?

    <p>Use for determining magnetic bearing with chain or compass survey</p> Signup and view all the answers

    What role does a spring brake play when using a prismatic compass?

    <p>To stabilize and stop needle oscillation for a quick reading</p> Signup and view all the answers

    In compass surveying, what is the main difference between true bearing and magnetic bearing?

    <p>True bearing is measured clockwise from true north, magnetic bearing is measured clockwise from magnetic north</p> Signup and view all the answers

    If a fore bearing is 120 degrees, what would the corresponding back bearing be according to the general rule?

    <p>240 degrees</p> Signup and view all the answers

    What is the relationship between back bearing (BA) and forward bearing (FB) when an observer relocates to another point?

    <p>BA = FB - 180 degrees</p> Signup and view all the answers

    When traversing with a compass survey, what is done at each point to ensure accuracy?

    <p>Reading the compass and taking a back bearing</p> Signup and view all the answers

    What does the Whole Circle Bearing System (W.C.B.) measure?

    <p>Bearing of survey lines wrt north or south line in a clockwise direction</p> Signup and view all the answers

    In the Quadrantal Bearing System (Q.B.), how are bearings of survey lines measured?

    <p>Wrt north or south line whichever is nearest in a clockwise or anticlockwise direction</p> Signup and view all the answers

    What is a Reduced Bearing (R.B.) in compass surveying?

    <p>Conversion of whole circle bearing into quadrantal bearing</p> Signup and view all the answers

    If a survey line has a Whole Circle Bearing (W.C.B.) of 30 degrees in the first quadrant, what would be its Reduced Bearing (R.B.)?

    <p>-30 degrees</p> Signup and view all the answers

    What would be the Quadrantal Bearing for a survey line with W.C.B. of 240 degrees in the fourth quadrant?

    <p>-60 degrees</p> Signup and view all the answers

    'What action should be taken if a Forward Bearing (FB) measures 290 degrees during traversing?' According to the general rule:

    <p>+180 to get Back Bearing (BB)</p> Signup and view all the answers

    Study Notes

    Linear Measurements Corrections

    • Correction for extension of chain or tape: This correction is applied to account for the extension of the chain or tape due to the applied pull force.
    • Temperature correction: This correction addresses errors arising from changes in temperature.
      • When the field temperature is less than the standardized temperature, the tape will contract.
      • The correction applied is subtractive, meaning it is deducted from the measured length.
    • Coefficient of linear expansion and recorded length: A higher coefficient of linear expansion indicates a greater change in length for a given temperature variation.
      • In temperature correction, if the coefficient of linear expansion is higher, the recorded length will be shorter than the actual length.
    • Pull correction: This corrects for discrepancies between the actual pull force used and the standard pull specified for the tape.
      • When the pull force is less than the standard pull, the tape is under tension, resulting in a shorter recorded length.
      • The correction in this case is additive, meaning it is added to the measured length.
    • Young's modulus of elasticity and extension: A higher Young's modulus of elasticity indicates greater stiffness in the material.
      • In linear measurements, if Young's modulus of elasticity increases, the extension of the chain or tape decreases.

    Sag Correction

    • Sag correction in tape or chain measurement: This correction addresses the sag or drooping of the tape or chain due to its weight when suspended between supports.

    Triangulation

    • Historical preference for triangulation: Triangulation was historically preferred for establishing control points because of its high accuracy and ability to cover large areas.
    • Primary trig points: Primary trig points were fixed at strong triangles with sides of 20 to 50 kilometers to form the foundation of triangulation networks.
    • Accuracy reduction in secondary networks: When transitioning from primary to secondary triangulation networks, there was a reduction in observational accuracy with the length of sides decreasing to between 10 and 20 kilometers.
    • Base line measurement in classical triangulation: Base lines were measured with high precision using invar tapes and special techniques.
    • Scale error in triangulation: The scale error in triangulation refers to the error in the measured length of the base line which propagates throughout the network.
    • Urban control station placement: In urban areas, control stations for roof-top triangulation are typically situated on tall buildings providing good visibility and stability.
    • Triangulation in open, hilly country: The main requirement for successful triangulation in open, hilly country is clear visibility between stations.

    Prismatic Compass

    • Prism movement: The up-and-down movement of the prism in a prismatic compass is used to adjust the height of the sighting for accurate readings.
    • Dark glasses and back vane: The dark glasses are swung in front of the back vane to reduce glare when taking observations in bright conditions.
    • Lifting pin and lever: The lifting pin and lever are used to detach the compass from its stand.
    • Mirror in front of forward vane: The mirror is positioned to reflect the forward vane's image into the prism, allowing for more accurate sightings.
    • Reading graduations: The graduated ring is used to read the magnetic bearing of the survey line.
    • Reflecting mirror: This mirror directs light from the forward vane towards the prism.
    • Convex faces and reflecting prism: The slightly convex faces of the 45º reflecting prism are used to reduce distortion and improve the clarity of the reflected image.
    • Prism mounting: The prism mounting, where the prism is held, is designed to be moved up and down between slides fixed on the outer case.
    • Circular aperture: A small circular aperture in the prism mounting allows the user to look directly through the prism.
    • Dark glasses for solar observations: Dark glasses are used in front of the back vane during solar observations to protect the user's eyesight.

    Jungle Area Obstacles

    • Obstructed chain line: When end stations are not visible from intermediate points due to dense jungle, offsetting is used.
      • This involves establishing offset points that are visible and chaining along these offsets.

    Compass Survey

    • Direction measurement: In compass surveys, directions of survey lines are typically measured by reading the magnetic bearings.
    • Obstructing chain line: A typical example of an obstacle obstructing chaining but not ranging is a river. The surveyor can determine the distance across the river by ranging but cannot physically walk across the river to chain the distance.
    • Rapid filling of detail: Plane tables are typically used for the rapid filling of detail in larger surveys and explanatory works.
    • Avoiding errors in compass surveys: To avoid errors in compass surveying, ensure the compass is properly leveled and centered.
    • Surveys requiring high accuracy: When a small area is surveyed with a high degree of accuracy, traverse surveying is preferred.

    Survey Stations

    • Optimum positioning: The best positions for survey stations should be selected to maximize visibility and minimize errors.

    Braced Quadrilaterals

    • Advantages of braced quadrilaterals: Braced quadrilaterals are advantageous in surveying because they allow for stronger geometric control and greater accuracy.

    Triangulation Method

    • Method used in triangulation: Trigonometric computations are inevitable when working with triangulation networks.

    Survey Target

    • Target requirements: A target used in surveying should be visible, stable, and easily identifiable for accurate measurements.

    Angles less than 25°

    • Angles less than 25°: When angles in a triangulation network are less than 25°, re-observation or adjustment to the network design is required.

    Ground for Survey Stations

    • Satisfactory ground for construction: Ensure the ground for long-term survey stations is stable, level, and free from erosion to ensure the longevity and accuracy of the network.
    • Signal lamps for high precision: Signal lamps might be used as targets in highly precise networks to improve visibility in challenging conditions.

    Prismatic Compass

    • Spring brake/brake pin: The spring brake or brake pin is used to secure the compass when not in use.
    • Centering check: To check centering:
      • rotate the compass 180 degrees.
      • If the needle points to the same mark after each rotation, the compass is centered.
    • Leveling: Leveling the compass in surveying is essential for accurate bearing readings.
    • Focusing: Focusing in a prismatic compass is achieved by adjusting the objective lens to obtain a clear image of the target.

    Magnetic Declination

    • Largest declination variation: The longitude of a location is the main cause of variation in magnetic declination.
    • Diurnal variation: Diurnal variation in magnetic declination refers to the daily fluctuations in compass readings due to solar activity.

    Magnetic Bearing

    • Magnetic bearing: A magnetic bearing in surveying is the angle measured clockwise from magnetic north to the survey line.
    • Magnetic meridian vs. true meridian: The magnetic meridian is the direction of magnetic north while the true meridian is the direction of true north.
    • Surveyor's compass: A surveyor's compass is distinguished by its magnetic needle which aligns with the magnetic meridian.

    Spring Brake

    • Role of the spring brake: The spring brake is used to hold the compass needle when taking readings and prevents unnecessary movement during observations.

    True Bearing and Magnetic Bearing

    • Difference in compass surveying: The main difference between a true bearing (TB) and a magnetic bearing (MB) is magnetic declination, which is the angle between true north and magnetic north.

    Forward Bearing and Back Bearing

    • General rule for back bearing: According to the general rule, the back bearing (BA) is 180 degrees more than the forward bearing (FB), except when FB is more than 180 degrees.
    • Relationship between BA and FB: When an observer moves to another point, the back bearing (BA) from the new point is 180 degrees different from the forward bearing (FB) of the same line from the previous point.

    Traversing

    • Accuracy check in traversing: At each point in a traverse survey, the compass reading is checked against the previously recorded magnetic bearing to ensure accuracy.

    Whole Circle Bearing System (W.C.B.)

    • W.C.B. measurement: The Whole Circle Bearing System (W.C.B.) measures the angle clockwise from north, starting at 0 degrees and going up to 360 degrees.

    Quadrantal Bearing System (Q.B.)

    • Q.B. measurement: The Quadrantal Bearing System (Q.B.) measures the angle of survey lines from north or south.

    Reduced Bearing (R.B.)

    • R.B. definition: Reduced Bearing (R.B.) is the smallest angle between the survey line and the meridian (north or south).
    • R.B. and W.C.B. conversion: A survey line with a Whole Circle Bearing (W.C.B.) of 30 degrees in the first quadrant has a Reduced Bearing (R.B.) of 30 degrees.

    Quadrantal Bearing with W.C.B.

    • Quadrantal Bearing conversion: If a survey line has a W.C.B. of 240 degrees in the fourth quadrant, its Quadrantal Bearing is S 60º W.

    Forward Bearing (FB)

    • Action for FB of 290 degrees: If a Forward Bearing (FB) measures 290 degrees during traversing, it indicates the observer is facing towards the South (the back bearing would be 110 degrees) .

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    Test your knowledge on corrections to linear measurements with a chain or tape including pull correction, temperature correction, standard length correction, sag correction, slope correction, and mean sea level correction. Explore how these corrections are applied for accurate measurements.

    More Like This

    Unit 4: Standard of Measurements
    40 questions

    Unit 4: Standard of Measurements

    SprightlyVision avatar
    SprightlyVision
    Linear Measurement Instruments in Industry
    40 questions

    Linear Measurement Instruments in Industry

    SprightlyVision avatar
    SprightlyVision
    Linear Measurement in Modern Industry
    40 questions

    Linear Measurement in Modern Industry

    SprightlyVision avatar
    SprightlyVision
    Linear Measurement in Modern Industry
    40 questions

    Linear Measurement in Modern Industry

    SprightlyVision avatar
    SprightlyVision
    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser