Lecture 1 Medium
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Questions and Answers

What is the first step the rodperson takes before observing TP3?

  • Record the HI reading for TP2
  • Rotate the instrument to observe TP2
  • Move the rod to a higher elevation
  • Set TP3 (correct)

How is the elevation for TP3 calculated?

  • Subtracting the FS rod reading from HI-3 (correct)
  • Averaging FS readings from TP1 and TP2
  • Finding the difference between TP2 and TP3 measurements
  • Adding the FS rod reading to HI-3

What is the FS rod reading observed for TP3?

  • 9.42’
  • 7.58’
  • 4.59’ (correct)
  • 5.81’

Which of the following should NOT be done after observing TP3?

<p>Set the instrument back to TP1 (D)</p> Signup and view all the answers

What is the corrected elevation for TP3 if HI-3 is 2305.16'?

<p>2301.55’ (A)</p> Signup and view all the answers

What is the sum of the backsight (BS) column values?

<p>40.40’ (A)</p> Signup and view all the answers

What is the published BM elevation given in the data?

<p>2303.45’ (A)</p> Signup and view all the answers

What is the misclosure value calculated from the closing BM elevation and the published BM elevation?

<p>-0.03’ (A)</p> Signup and view all the answers

What is the ending elevation calculated using the formula: BM + (sum of BSs) + (sum of FSs)?

<p>2303.42’ (B)</p> Signup and view all the answers

Which Foresight (FS) value is the highest recorded in the data?

<p>8.50’ (C)</p> Signup and view all the answers

What do the large red numbers on the level rod represent?

<p>Whole feet (B)</p> Signup and view all the answers

What is the purpose of the horizontal crosshair in leveling?

<p>To provide a reference point for rod reading (C)</p> Signup and view all the answers

Which equation is used to express the deviation from a horizontal line due to Earth's curvature?

<p>c = 0.667(M)² (A)</p> Signup and view all the answers

How does one determine the hundredth portion of the reading on the level rod?

<p>By counting the black hack marks (C)</p> Signup and view all the answers

What is the significance of measuring the horizontal distance in miles in the curvature equation?

<p>It helps in calculating the corrected rod reading (C)</p> Signup and view all the answers

If the horizontal distance from the instrument to the level rod is 1625 feet, how many miles is that?

<p>0.3086 miles (D)</p> Signup and view all the answers

What additional component is emphasized in the lab portion of this course?

<p>Understanding of level rod readings (D)</p> Signup and view all the answers

Which of the following best describes a level surface?

<p>A surface that is consistent with a horizontal line (D)</p> Signup and view all the answers

What is the corrected elevation for TP3 after the setup and BS reading?

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

How is the HI-4 value calculated?

<p>By adding BS rod reading to TP3 elevation (C)</p> Signup and view all the answers

What is the elevation of BM A?

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

Which value indicates the BS reading before the last setup?

<p>4.59’ (A)</p> Signup and view all the answers

What represents the difference between TP1 and BM A in terms of elevation?

<p>6.84’ (C)</p> Signup and view all the answers

What is the total reading for FS for TP2?

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

What is the elevation for TP2 after correcting for the BS reading?

<p>2314.42’ (A)</p> Signup and view all the answers

What does the abbreviation HI stand for in this context?

<p>Height of Instrument (A)</p> Signup and view all the answers

What is the value of M when the horizontal distance is 1625 feet?

<p>0.307765152 miles (C)</p> Signup and view all the answers

What is the formula used to calculate c based on M?

<p>c = (0.667)(M)² (B)</p> Signup and view all the answers

What is the corrected rod reading after considering the curvature departure?

<p>10.45' (A)</p> Signup and view all the answers

When calculating c with the formula c = 0.0239(F)², what value is used for F when the horizontal distance is 1625-feet?

<p>1.625 (B)</p> Signup and view all the answers

What is the numerical result of c when using F equals 1.625 in the equation c = 0.0239(F)²?

<p>0.06' (C)</p> Signup and view all the answers

Which of the following equations is correct for Cm when K is expressed in kilometers?

<p>Cm = 0.0785(K)² (A)</p> Signup and view all the answers

What effect does the curvature of the level surface have on reading the level rod?

<p>It results in reading too high. (C)</p> Signup and view all the answers

Which of the following correctly describes the steps to find the corrected rod reading?

<p>Subtract c from the initial reading. (A)</p> Signup and view all the answers

What is the closing elevation on BM A after observing the FS rod reading?

<p>2303.42’ (B)</p> Signup and view all the answers

How is the closing elevation on BM A calculated?

<p>HI - FS (B)</p> Signup and view all the answers

What is the FS reading observed on BM A?

<p>13.95’ (D)</p> Signup and view all the answers

What does the abbreviation 'HI' represent in this context?

<p>Height of Instrument (B)</p> Signup and view all the answers

Which of the following is true about the process after recording the FS reading?

<p>The level loop is completed. (C)</p> Signup and view all the answers

What is the misclosure of the level loop?

<p>It is a measure of how accurate the calculations are. (A)</p> Signup and view all the answers

What elevation corresponds to TP4 before any measurements are taken?

<p>2317.37’ (D)</p> Signup and view all the answers

Which reading is required for calculating the closing elevation for BM A?

<p>Foresight (FS) (D)</p> Signup and view all the answers

Which component is essential before finalizing the level notes?

<p>Completing the Page Check (A)</p> Signup and view all the answers

What is recorded on the level rod after rotating the instrument on BM A?

<p>Foresight Reading (A)</p> Signup and view all the answers

Flashcards

Curvature correction

The difference in elevation between a level surface and a horizontal line (line of sight) due to the Earth's curvature.

Curvature correction formula (miles)

A formula used to calculate the curvature correction when the horizontal distance is expressed in miles (M).

Curvature correction formula (thousands of feet)

A formula used to calculate the curvature correction when the horizontal distance is expressed in thousands of feet (F).

Curvature correction formula (kilometers)

A formula used to calculate the curvature correction when the horizontal distance is expressed in kilometers (K).

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Correcting the rod reading

The process of adjusting the initial level rod reading to account for the curvature correction.

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Curvature correction

The difference in elevation between a level surface and a horizontal line (line of sight) due to the Earth's curvature.

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Initial rod reading

The reading on the level rod before any corrections are applied.

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Corrected rod reading

The reading on the level rod after accounting for the curvature correction.

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Curvature (c)

The deviation of a horizontal line from a level surface caused by the Earth's curvature.

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Horizontal distance (HD)

The distance between the instrument and the level rod, measured in miles.

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Differential leveling

The difference in elevation between two points, determined using a level and a level rod.

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Initial reading on level rod

The initial reading on a level rod before any corrections are applied.

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c = 0.667(M)²

The formula used to calculate the correction for curvature, where the horizontal distance is expressed in miles.

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Level rod

A specific type of level rod used in surveying, with markings that help determine elevations accurately.

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Level

A device used in surveying to establish a horizontal line of sight.

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Elevation

The height of a point above a reference point, typically sea level. In surveying, it is commonly used to determine the elevation of points on the ground.

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HI (Height of Instrument)

The point at which the instrument is set up to measure the elevation of other points. The instrument, typically a level, is positioned at the HI to provide a consistent reference point for measurements.

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FS (Foresight) reading

The reading on the level rod observed by the instrument when it is aimed at a specific point. The FS reading is part of the calculation to determine the elevation of that point.

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TP (Turning Point)

A temporary point established during surveying, often marked with a stake or a pin, used as a reference point for further measurements.

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Elevation Calculation

The elevation of a point can be determined by subtracting the FS rod reading from the HI.

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Sum of Backsights (BS)

Sum of all backsight readings in a level run.

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Sum of Foresights (FS)

Sum of all foresight readings in a level run.

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Page Check

A method of comparing the starting and ending elevations of a level run to check for errors.

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Misclosure

The difference between the closing elevation and the published elevation of a benchmark.

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Benchmark (BM)

A point with a known elevation used as a reference point for leveling surveys.

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Turning Point (TP)

The starting point of a level loop, where the instrument is set up to observe the backsight.

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Height of Instrument (HI)

The difference in elevation between the instrument's height and the backsight rod reading.

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Backsight (BS)

A reading taken on a rod when the level instrument is sighted back towards the previous TP or BM.

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Foresight (FS)

A reading taken on a rod when the level instrument is sighted forward to a new TP or BM.

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Difference in Elevation (Elevation Difference)

The difference between the HI and the FS reading, used to calculate the elevation of a point.

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Accuracy Requirement

A specific level of precision or tolerance allowed for a level loop, often defined in units of feet or meters.

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Corrected Elevation

The elevation of a point determined by subtracting the FS reading from the HI.

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TP3 Elevation Calculation

The elevation of a point is the vertical distance of that point from a reference datum, typically mean sea level. In this case, the elevation of TP3 is determined by subtracting the backsight reading from the previous HI, which is the height of the instrument.

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HI-3 Calculation

The HI is the height of the telescope of the instrument from a known point of elevation. It is calculated by adding the backsight reading to the known elevation of the previous point - in this case, TP2.

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Backsight Reading

The backsight reading is the measurement taken on a known point when setting up the instrument. It is used to determine the HI of the instrument. It is recorded as a positive value in the field book.

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Foresight Reading

The foresight reading is the measurement taken on an unknown point with the instrument set up. It is used to determine the elevation of the point. It is recorded as a negative value in the field book.

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IFS Reading

The foresighted intermediate is the measurement taken on an unknown point in between known points with the instrument set up. It is used to determine the elevation of the point. It is recorded as a negative value in the field book.

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Elevation Determination

Once the HI is determined for a new instrument setup (HI-4) the elevation of a new point can be determined by subtracting the FS reading from the new HI.

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Field Book

The field book is a record of all the measurements taken during a survey. It includes the station name, the BS readings, the FS readings, and the calculated elevations of the points.

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Study Notes

Leveling - Theory, Methods, and Equipment

  • Objectives: Understanding leveling terms, vertical datums, curvature and refraction effects, and differential leveling corrections.

  • Work Required: Review sections 4.1 through 4.5.2, and complete problems 4.1, 4.2 (using distances of 850 feet, 1387 feet, and 2100 feet), and 4.6.

4.1 Introduction

  • Leveling: A general term for processes determining elevations or differences in elevation.

  • Applications: Used for mapping, engineering design, highway/railroad design, water systems, earthwork calculations, drainage, and earth/crustal motion studies.

4.2 Definitions

  • Vertical Line: Follows the local direction of gravity (plumb line).

  • Level Surface: A curved surface perpendicular to the vertical line at every point. Water surfaces are close approximations.

  • Level Line: A line within a level surface.

  • Horizontal Plane: A plane perpendicular to the vertical line.

  • Horizontal Line: A line within a horizontal plane.

  • Vertical Datum: A reference level surface (e.g., mean sea level). Elevations are referenced relative to this surface.

  • Elevation: The vertical distance from a datum to a point or object.

4.3 North American Vertical Datums (NGVD29 and NAVD88)

  • NGVD29 (National Geodetic Vertical Datum of 1929): A previous vertical datum based on mean sea level, used in much of North America.

  • NAVD88 (North American Vertical Datum of 1988): The current vertical datum. It uses a single benchmark as a reference point (Father Point, Quebec).

  • Tidal Datums: Datums used in coastal areas, often referencing mean high water to establish property boundaries.

  • Benchmarks (BM): Permanent points with known elevations, used as references.

4.4 (a) Curvature (c) for Differential Leveling

  • Curvature: The Earth's curvature causes the horizontal plane to depart from a level surface.

  • Curvature Correction (c): An equation corrects for the curvature of the Earth; c = 0.667(M)² where M is the horizontal distance in miles. Or, c = 0.0239(F)2 where F is the horizontal distance in thousands of feet.

4.4 (b) Curvature and Refraction (c+r) for Differential Leveling

  • Refraction: Atmospheric refraction causes light rays to bend, affecting the apparent height of the rod.

  • Combined Curvature and Refraction Correction (c + r): A correction equation that accounts for both curvature and refraction; c+r = 0.574(M)² Or c+r = 0.0206(F)²

4.5 Methods for Determining Differences in Elevation

  • Differential Leveling: Employs a series of benchmarks, backsights, and foresights to measure elevation differences; different methods like taping, barometric methods, trigonometric leveling and electronic techniques are also introduced.

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Leveling-Theory, Methods, and Equipment PDF

Description

Test your understanding of leveling concepts, including vertical datums, curvature effects, and differential leveling corrections. This quiz covers key definitions and applications of leveling relevant to engineering and mapping tasks. Review sections 4.1 through 4.5.2 before attempting the problems.

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