Lecture 1
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Questions and Answers

What is the elevation of Point A if it is noted as 802.46-feet above the reference datum?

  • 802.46 meters
  • Zero feet
  • 802.46 feet (correct)
  • 850.46 feet

    • Which datum is currently used in North America as a reference for elevations?

  • National Vertical Datum of 1929
  • North American Vertical Datum of 1988 (correct)
  • Mean Sea Level
  • Geoid

    • What does the term 'mean sea level (MSL)' refer to?

  • The level of the sea during a storm surge
  • The lowest recorded point of the sea surface
  • The highest point of tidal influence
  • The average height of the sea surface for all stages of the tide over a lunar cycle (correct)

    • What is a benchmark (BM) in relation to elevation measurement?

    <p>A fixed point where elevation is known or assumed</p> Signup and view all the answers

    What is the primary purpose of tidal datums?

    <p>To establish property boundaries and drilling rights</p> Signup and view all the answers

    Which method is often debated in court regarding tidal datums?

    <p>The interpretation and determination of tidal datum definitions</p> Signup and view all the answers

    What is the average height of mean high water (MHW)?

    <p>The average sea level during high tide</p> Signup and view all the answers

    Which item is NOT considered a benchmark (BM)?

    <p>A movable fishing boat</p> Signup and view all the answers

    What should be done to the initial rod reading after correcting for curvature and refraction?

    <p>Subtract the correction from the initial reading.</p> Signup and view all the answers

    What is the constant used in the equation for combined effects of curvature and refraction in terms of miles?

    <p>0.574</p> Signup and view all the answers

    If the horizontal distance (HD) is 1625 feet, what value of M is used in the curvature and refraction equation?

    <p>0.307</p> Signup and view all the answers

    What does the term c+r represent in the context of leveling?

    <p>The correction for curvature and refraction.</p> Signup and view all the answers

    How is the correction for curvature expressed in the context of distances measured in feet?

    <p>0.0206(F)²</p> Signup and view all the answers

    Which of the following is added to the initial reading to account for curvature when HD is 1625 feet?

    <p>0.05'</p> Signup and view all the answers

    Which equation represents the curvature and refraction correction for horizontal distances in kilometers?

    <p>c+r = 0.011(K)²</p> Signup and view all the answers

    What is the corrected elevation for TP3?

    <p>2309.83'</p> Signup and view all the answers

    What is the corrected rod reading if the initial reading is 10.51 feet and the correction is 0.05 feet?

    <p>10.46 feet</p> Signup and view all the answers

    What value is added to calculate HI-4 for TP3?

    <p>BS rod reading of 6.45'</p> Signup and view all the answers

    What is the HI for TP1?

    <p>2310.97'</p> Signup and view all the answers

    What does the value of 4.59' represent in relation to TP3?

    <p>Difference in elevation</p> Signup and view all the answers

    What is the BS reading for TP1?

    <p>9.42'</p> Signup and view all the answers

    Which value is not related to the elevation for the BM A point?

    <p>7.58'</p> Signup and view all the answers

    What is the sum of the CP3 elevation and the first BS reading used in the calculation?

    <p>2316.28'</p> Signup and view all the answers

    What is the corrected elevation at the point marked as BM A?

    <p>2309.13'</p> Signup and view all the answers

    Which TP has an elevation of 2314.42'?

    <p>TP2</p> Signup and view all the answers

    How much is the elevation difference between 2310.97' and 2309.13'?

    <p>0.84'</p> Signup and view all the answers

    What is the elevation at TP1?

    <p>5.68'</p> Signup and view all the answers

    At which height is TP2 supposed to be set?

    <p>2310.97'</p> Signup and view all the answers

    What is the elevation at the lowest marked point?

    <p>2301.55'</p> Signup and view all the answers

    What is the highest elevation indicated in the document?

    <p>2310.97'</p> Signup and view all the answers

    What is the distance between the corrected elevation at TP1 and the corrected elevation at TP2?

    <p>4.26'</p> Signup and view all the answers

    If the elevation at TP1 is 5.68', what is the elevation at the point immediately above it at 9.42'?

    <p>2.74'</p> Signup and view all the answers

    What is the purpose of the graduated pole or rod in construction measurements?

    <p>To replace the tape for measuring vertical distances</p> Signup and view all the answers

    In differential leveling, what is the first step in the process?

    <p>Setting up and leveling the instrument</p> Signup and view all the answers

    What does a backsight (BS) reading represent in differential leveling?

    <p>A plus sight that is added to the benchmark elevation</p> Signup and view all the answers

    What is implied by using a turning point (TP) in differential leveling?

    <p>It is a semi-permanent hard surface for foresight readings</p> Signup and view all the answers

    How is the height of the instrument (HI) determined in differential leveling?

    <p>It is obtained by adding the backsight reading to the benchmark elevation</p> Signup and view all the answers

    What should be done to correct for curvature and refraction in differential leveling?

    <p>Ensure distances are equal for backsight and foresight readings</p> Signup and view all the answers

    What is the main application of differential leveling mentioned?

    <p>Running levels for multistory building construction</p> Signup and view all the answers

    What reading is taken after the backsight reading in the leveling procedure?

    <p>A foresight (FS) rod reading on the turning point</p> Signup and view all the answers

    What is the elevation of TP4 after the FS rod reading is taken?

    <p>2307.78’</p> Signup and view all the answers

    What is the HI value recorded for TP3?

    <p>2316.28’</p> Signup and view all the answers

    How do you compute the elevation for TP4?

    <p>Subtract the FS reading from HI-4</p> Signup and view all the answers

    Which rod person action is performed before setting TP4?

    <p>Rotate the instrument to observe TP3</p> Signup and view all the answers

    Which elevation is associated with TP1?

    <p>2309.13’</p> Signup and view all the answers

    What is the FS rod reading for TP2?

    <p>5.81’</p> Signup and view all the answers

    Which TP has the highest HI value among the listed?

    <p>TP3</p> Signup and view all the answers

    Study Notes

    Leveling - Theory, Methods, and Equipment

    • Objectives:
      • Understanding leveling terminology
      • Understanding differences in vertical datums
      • Understanding the effects of curvature and refraction on leveling
      • Understanding how to correct for the effects of curvature and refraction in differential leveling

    Work Required

    • Read sections 4.1 through 4.5.2
    • Complete problems 4.1, 4.2, using distances of 850 feet, 1387 feet, and 2100 feet, and problem 4.6.

    4.1 Introduction

    • Leveling is a process for determining elevations of points or differences in elevation
    • Used for mapping, engineering design, and construction
    • Applications include highway, railroad, canal, and water system design; earthwork calculations; and land evaluation
    • Leveling involves various processes to establish vertical datum

    4.2 Definitions

    • Vertical Line: A line following the local direction of gravity (plumb line)
    • Level Surface: A curved surface perpendicular to the local vertical line at every point; a body of still water is a close approximation
    • Level Line: A line within a level surface
    • Horizontal Plane: A plane perpendicular to the local vertical line
    • Horizontal Line: A line within a horizontal plane
    • Vertical Datum: A reference level surface (e.g., average sea level) from which elevations are measured
    • Elevation: The vertical distance from a vertical datum to a point or object

    4.3 North American Vertical Datums (NGVD29 and NAVD88)

    • NGVD29: A previous vertical datum based on mean sea level at specific locations
    • NAVD88: A more accurate vertical datum, adjusted to account for improved data and changes in sea level and Earth's crust
    • Based on a single benchmark in Canada

    4.4 Curvature

    • A level surface is curved due to the Earth's curvature.
    • An instrument's line of sight is horizontal, not a level surface due to curvature effects.
    • Corrections need to be applied to measurements involving significant horizontal distances

    4.4 (a) Curvature (c)

    • Equation for curvature correction (c) using horizontal distance (M) in miles: c = 0.667(M)²
    • Equation using horizontal distance in thousands of feet (F): c = 0.0239(F)².
    • Correction must be subtracted to obtain accurate results.

    4.4 (b) Curvature and Refraction

    • Refraction causes light rays (and thus the instrument's line of sight) to bend toward the Earth's surface.
    • Combined effect of curvature and refraction (c+r) for horizontal distances (M) in miles to the level rod: c+r = 0.574(M)²
      • Correction must be subtracted from initial rod reading to compensate for curvatures and refractions effects

    4.5 Measuring Vertical Distances (Taping/Electronic Methods)

    • Measures a vertical line using taping or EDM techniques
    • Typically used for shorter distances or when precision is not as critical

    4.5.2 Differential Leveling

    • Method to measure differences in vertical elevation between two or more points.
    • Uses a level instrument and rod
    • Establish a benchmark with a known elevation and measures the elevation from the instrument.
    • Requires taking multiple measurements to create a "loop" for verifying calculations and accuracy of the data.

    Example Differential Leveling Notes

    • Data recording format for differential leveling
    • Includes columns for Station, Backsight (BS), Height of Instrument (HI), Foresight (FS), Intermediate Foresight (IFS), Elevation, and Corrected Elevation
    • Describes procedures of using Backsight (BS), Foresight (FS), and Height of Instrument (HI) for calculating elevations of unknown points for differential levelings

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    Leveling-Theory, Methods, and Equipment PDF

    Description

    Test your understanding of leveling terminology, vertical datums, and the effects of curvature and refraction on leveling. This quiz covers key concepts from sections 4.1 to 4.5.2, along with problem-solving applications in mapping and engineering design.

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