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Questions and Answers
What is the value of 'M' when calculating for 1625 feet?
What is the value of 'M' when calculating for 1625 feet?
- 0.307 (correct)
- 0.325
- 0.303
- 0.310
The corrected rod reading after accounting for curvature is 10.51'.
The corrected rod reading after accounting for curvature is 10.51'.
False (B)
What is the formula used to calculate 'c' when using the value of 'F'?
What is the formula used to calculate 'c' when using the value of 'F'?
c = 0.0239(F)²
The initial reading on the level rod was ___ feet.
The initial reading on the level rod was ___ feet.
Match the following equations with their corresponding variables:
Match the following equations with their corresponding variables:
What would the value of 'c' be when 'F' equals 1.625?
What would the value of 'c' be when 'F' equals 1.625?
The departure from the horizontal line at 1625 feet is 0.06'.
The departure from the horizontal line at 1625 feet is 0.06'.
What is the corrected rod reading after making the adjustment?
What is the corrected rod reading after making the adjustment?
What is the elevation of the Temporary Benchmark (TBM) after running the levels?
What is the elevation of the Temporary Benchmark (TBM) after running the levels?
It is unnecessary to set multiple Temporary Benchmarks (TBMs) at the job site.
It is unnecessary to set multiple Temporary Benchmarks (TBMs) at the job site.
What is the formula to find the elevation on the Temporary Benchmark (TP)?
What is the formula to find the elevation on the Temporary Benchmark (TP)?
The elevation of the benchmark (BM) is __________.
The elevation of the benchmark (BM) is __________.
Match the following components with their meanings:
Match the following components with their meanings:
What is the purpose of closing the level loop?
What is the purpose of closing the level loop?
What is the purpose of establishing a turning point (TP)?
What is the purpose of establishing a turning point (TP)?
What is recorded in the BS (+) column of level note keeping?
What is recorded in the BS (+) column of level note keeping?
The foresight (FS) rod reading is taken on an object of known elevation.
The foresight (FS) rod reading is taken on an object of known elevation.
What is the computed elevation for TP1?
What is the computed elevation for TP1?
Only the foot part of the backsight rod reading needs to be recorded if it is below 1 foot.
Only the foot part of the backsight rod reading needs to be recorded if it is below 1 foot.
Once a suitable turning point is established, the level rod is placed on the ______.
Once a suitable turning point is established, the level rod is placed on the ______.
What should be done if a hard surface cannot be found for the turning point?
What should be done if a hard surface cannot be found for the turning point?
Match the following components with their roles in the leveling process:
Match the following components with their roles in the leveling process:
What is the rod reading on TP1?
What is the rod reading on TP1?
TP1 elevation is calculated by adding the foresight rod reading to HI-1.
TP1 elevation is calculated by adding the foresight rod reading to HI-1.
What is the computed HI-5 based on the provided BS reading and elevation for TP4?
What is the computed HI-5 based on the provided BS reading and elevation for TP4?
The BS reading observed on TP4 is 9.26’.
The BS reading observed on TP4 is 9.26’.
What elevation is associated with TP3?
What elevation is associated with TP3?
What was the FS rod reading observed for TP2?
What was the FS rod reading observed for TP2?
The HI-5 for TP4 is calculated by adding the BS rod reading of ______ to the elevation.
The HI-5 for TP4 is calculated by adding the BS rod reading of ______ to the elevation.
The elevation for TP2 was calculated by adding the FS rod reading to HI-2.
The elevation for TP2 was calculated by adding the FS rod reading to HI-2.
Match the following terms with their definitions:
Match the following terms with their definitions:
HI-3 is calculated by adding the BS rod reading to the elevation for TP2, resulting in HI-3 = ____.
HI-3 is calculated by adding the BS rod reading to the elevation for TP2, resulting in HI-3 = ____.
Which of the following stations has the lowest corrected elevation?
Which of the following stations has the lowest corrected elevation?
Match the following values to their corresponding terms:
Match the following values to their corresponding terms:
The corrected elevation for TP1 is 2309.13’.
The corrected elevation for TP1 is 2309.13’.
What is the BS reading for TP2?
What is the BS reading for TP2?
What is the elevation for TP2 after calculation?
What is the elevation for TP2 after calculation?
The BS rod reading for TP2 was 9.42’.
The BS rod reading for TP2 was 9.42’.
What does the abbreviation FS stand for in leveling?
What does the abbreviation FS stand for in leveling?
What is the corrected elevation at the point marked as TP1?
What is the corrected elevation at the point marked as TP1?
The elevation at the point marked as BM A is lower than the elevation at TP1.
The elevation at the point marked as BM A is lower than the elevation at TP1.
What is the elevation listed for TP2?
What is the elevation listed for TP2?
The elevation at BM A is _____ feet.
The elevation at BM A is _____ feet.
Match the following points with their marked elevations:
Match the following points with their marked elevations:
What is the elevation difference between TP1 and the final point?
What is the elevation difference between TP1 and the final point?
The rodperson would move backward to set TP2.
The rodperson would move backward to set TP2.
What is the lowest marked elevation in the provided content?
What is the lowest marked elevation in the provided content?
Flashcards
Curvature Correction (c)
Curvature Correction (c)
The amount of correction needed for the curvature of the Earth when measuring distances with a level.
Horizontal Distance (HD)
Horizontal Distance (HD)
The horizontal distance from the leveling instrument to the point where the level rod is held.
Initial Rod Reading
Initial Rod Reading
The initial reading on the level rod before any corrections are applied.
Corrected Rod Reading
Corrected Rod Reading
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Curvature Correction Formula (miles)
Curvature Correction Formula (miles)
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Curvature Correction Formula (thousands of feet)
Curvature Correction Formula (thousands of feet)
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Curvature Correction Formula (kilometers)
Curvature Correction Formula (kilometers)
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Reading the Rod Too High
Reading the Rod Too High
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Benchmark (BM)
Benchmark (BM)
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Height of Instrument (HI)
Height of Instrument (HI)
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Backsight (BS)
Backsight (BS)
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Foresight (FS)
Foresight (FS)
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Temporary Benchmark (TBM)
Temporary Benchmark (TBM)
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Closing the Level Loop
Closing the Level Loop
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Elevation Difference
Elevation Difference
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Differential Leveling
Differential Leveling
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Turning Point (TP)
Turning Point (TP)
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Elevation of a point
Elevation of a point
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Setting TP2
Setting TP2
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Level
Level
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Leveling
Leveling
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Elevation
Elevation
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Instrument Height (HI)
Instrument Height (HI)
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Calculating Elevation
Calculating Elevation
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Moving the Level
Moving the Level
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HI (Height of Instrument)
HI (Height of Instrument)
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Level Rod
Level Rod
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Interpolated Elevation (IFS)
Interpolated Elevation (IFS)
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Study Notes
Leveling - Theory, Methods, and Equipment
- Leveling is the process of determining elevations of points or differences in elevation.
- Essential for mapping, engineering design, and construction.
- Used for: designing highways, railroads, canals, sewers; calculating earthwork volumes; and studying land movement.
- Vertical line follows the local direction of gravity (plumb line).
- Level surfaces are curved, approximately spheroidal.
- Bodies of still water approximate level surfaces.
- Level lines are within level surfaces (curved).
- Horizontal plane is perpendicular to the vertical line.
- Horizontal lines are within horizontal planes.
- Vertical datum is a reference level surface (e.g., mean sea level).
- Elevation is the vertical distance from the vertical datum to a point.
- Elevation/height is measured relative to the datum.
Curvature and Refraction
- The Earth is curved, causing horizontal lines to deviate from level lines.
- Refraction (bending of light rays in the atmosphere) further affects the level lines.
- Curvature and refraction corrections need to be considered in leveling calculations.
- Corrections are based on the horizontal distance between the instrument and the rod.
- These corrections are subtracted from initial measurements to get corrected values.
Differential Leveling
- Process of finding elevation differences.
- Involves successive backsight and foresight observations.
- Benchmarks are used as reference points.
- Rod readings (BS, FS) are taken using a level instrument.
- Instrument height (HI) is calculated.
- Elevations are calculated by adding or subtracting rod readings from the instrument height.
Datums
- NGVD29: A past North American vertical datum, based on mean sea level.
- NAVD88: The current North American vertical datum, using a single benchmark.
- Key Differences: NGVD29 is based on the average of tidal measurements across many sites whereas NAVD88 was adjusted to encompass additional measurements.
Level Rods and Readings
- Fiber glass level rods with marked lines for precise readings.
- Red numbers indicate feet; black numbers indicate tenths of a foot; and black lines indicate hundredths of a foot.
- Backsights are on known points; foresights are on unknown points.
Benchmarking
- Permanent physical markers, often set in concrete, whose elevation is known.
- Establishing a network of benchmarks provides a reference system for leveling.
Methods and Procedures
- Clear procedures are necessary for recording and calculating elevations correctly.
- Backsight plus elevation equals height of instrument (HI).
- HI minus foresight equal elevation or elevation plus foresight equals height of instrument (HI).
- Differential leveling involves measuring elevations relative to known points using an instrument for successive measurements
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