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?

Set the instrument back to TP1 Signup and view all the answers

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

2301.55’ Signup and view all the answers

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

40.40’ Signup and view all the answers

What is the published BM elevation given in the data?

2303.45’ Signup and view all the answers

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

-0.03’ Signup and view all the answers

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

2303.42’ Signup and view all the answers

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

8.50’ Signup and view all the answers

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

Whole feet Signup and view all the answers

What is the purpose of the horizontal crosshair in leveling?

To provide a reference point for rod reading Signup and view all the answers

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

c = 0.667(M)² Signup and view all the answers

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

By counting the black hack marks Signup and view all the answers

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

It helps in calculating the corrected rod reading 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?

0.3086 miles Signup and view all the answers

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

Understanding of level rod readings Signup and view all the answers

Which of the following best describes a level surface?

A surface that is consistent with a horizontal line Signup and view all the answers

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

2316.28’ Signup and view all the answers

How is the HI-4 value calculated?

By adding BS rod reading to TP3 elevation Signup and view all the answers

What is the elevation of BM A?

2309.13’ Signup and view all the answers

Which value indicates the BS reading before the last setup?

4.59’ Signup and view all the answers

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

6.84’ Signup and view all the answers

What is the total reading for FS for TP2?

5.81’ Signup and view all the answers

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

2314.42’ Signup and view all the answers

What does the abbreviation HI stand for in this context?

Height of Instrument Signup and view all the answers

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

0.307765152 miles Signup and view all the answers

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

c = (0.667)(M)² Signup and view all the answers

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

10.45' 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?

1.625 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?

0.06' Signup and view all the answers

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

Cm = 0.0785(K)² Signup and view all the answers

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

It results in reading too high. Signup and view all the answers

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

Subtract c from the initial reading. Signup and view all the answers

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

2303.42’ Signup and view all the answers

How is the closing elevation on BM A calculated?

HI - FS Signup and view all the answers

What is the FS reading observed on BM A?

13.95’ Signup and view all the answers

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

Height of Instrument Signup and view all the answers

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

The level loop is completed. Signup and view all the answers

What is the misclosure of the level loop?

It is a measure of how accurate the calculations are. Signup and view all the answers

What elevation corresponds to TP4 before any measurements are taken?

2317.37’ Signup and view all the answers

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

Foresight (FS) Signup and view all the answers

Which component is essential before finalizing the level notes?

Completing the Page Check Signup and view all the answers

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

Foresight Reading Signup and view all the answers

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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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.