Case Studies: Concepts in Distance Measurement
Case Study 1: Choosing a Measurement Method
Example
A surveyor needs to determine the distance between two points under three different scenarios:
- A rough estimate for a preliminary route survey through a densely wooded area.
- A precise measurement across a busy 100-meter wide highway where traffic cannot be stopped.
- A highly accurate baseline measurement for a geodetic control network over flat terrain.
Recommend the most appropriate method for horizontal distance measurement for each scenario.
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Case Study 2: Understanding Tape Corrections
Example
During a taping operation, a surveyor uses a steel tape that was standardized at with a pull of fully supported.
Explain whether the measured distance recorded in the field book will be too long or too short compared to the true distance under the following conditions:
- The field temperature is .
- The tape is supported only at the ends (0m and 50m marks).
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Solved Problems: Taping and Optical Computations
Problem 1: Pacing Calculations (Basic)
Example
A surveyor walked a course 5 times with the following number of paces: 62, 63, 61, 64, and 62.
They then walked an unknown distance with the following paces: 145, 148, 146, and 147.
Determine the surveyor's pace factor and the approximate distance of line .
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Problem 2: Temperature Correction (Intermediate)
Example
A steel tape is standardized at . A line is measured with this tape and found to be at an average field temperature of .
The coefficient of linear expansion for steel is .
Calculate the total temperature correction and the corrected length of the line.
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Problem 3: Sag and Pull Corrections (Advanced)
Example
A tape weighing (total mass ) is standardized under a pull of . The cross-sectional area is and .
During measurement, the tape is supported only at its ends ( and ) and a pull of is applied.
Calculate the pull correction () and the sag correction () for one tape length. Determine the effective length of the tape under these conditions.
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Problem 4: Normal Tension (Advanced)
Example
Using the data from Problem 3 (, , , , ), determine the Normal Tension () required to make the elongation from pull exactly counteract the shortening from sag.
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Problem 5: Stadia Measurement (Intermediate)
Example
A transit is set up over point A. A stadia rod is held vertically at point B.
The transit has a stadia interval factor () of 100 and a stadia constant () of 0.30 m.
The upper stadia hair reading is 2.450 m and the lower stadia hair reading is 1.150 m. The line of sight is horizontal.
Determine the horizontal distance from the transit to the rod.
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