45 Questions
Where are distances obtained by pacing sufficiently accurate?
Surveying, engineering, geology, agriculture, forestry, and military field sketching
What is a passometer?
A tool used for measuring distances by counting steps
What is an odometer used for?
Converting the number of revolutions of a wheel to a distance
What is a measuring wheel used for?
Measuring distances along irregular or curved lines and boundaries
What is a chaining method?
A method of measuring distances using a chain or tape
What is a cloth tape used for?
Ordinary work
What is a metallic tape used for?
All survey works
What is a steel tape used for?
Standardizing chains and construction work
What is the limitation of a cloth tape?
It is affected by moisture and shrinks
What is invar tape primarily used for?
Measuring distances with maximum precision
What is the purpose of an inclinometer or clinometer?
To measure angles of slope, elevation, or depression
What should be done to steel tapes after use in wet weather?
Clean and dry them with an oily rag
Why should a piece of colored cloth be tied to an arrow?
To enable the arrow to be seen clearly on the field
What should be done to ranging rods?
Erect them as vertically as possible at the exact station point
What is the fundamental purpose of studying errors in surveying?
To understand the sources of errors and apply corrections to minimize their effect
Why should the operating tension of a steel band be indicated?
To ensure the tape is not damaged
How often should linen tapes be tested for length?
Frequently and always after repairs
What is the main difference between an error and a mistake in surveying?
Error is a deviation from the exact value, while mistake is a blunder made by the surveyor
Which of the following is an instrumental error in taping?
Kinks in the tape
What is the ranging process?
The process of establishing intermediate points on a straight line
What is the effect of sag in the chain or tape on the measurement?
Cumulative +
When is direct ranging done?
When the two ends of the survey lines are inter visible
What is the purpose of ranging alignment in chaining?
To ensure the tape is aligned with the direction of measurement
Which of the following is a personal error in taping?
Tapeperson reading the tape incorrectly
What is the effect of non-horizontal alignment of the tape during measurement?
Cumulative +
Which of the following is an example of a mistake in chaining?
Displacement of arrows and not replacing them in proper position
What is the main reason for booking of data in surveying?
To record the measurements for future reference
What is the actual length of the standard tape in the given example?
30.003
What is the temperature at which tapes are usually standardized?
20ºC
What is the coefficient of expansion of Invar tapes?
0.50 × 10−6 per ℃
What is the formula for temperature correction?
Ct = ∝ × L × ΔT
What is the principle of Chain Triangulation?
Dividing the area into small triangles
What is the measured length of the line AB in the given example?
348.28
What is the error in the tape used to measure the line AB in the given example?
0.05 m
When is chain surveying suitable?
When the area to be surveyed is small and has simple details
What is the purpose of tie lines in chain surveying?
To locate interior details
What is the temperature of the steel tape in the given example?
27ºC
What is the main and longest line in chain surveying called?
Base line
What is the coefficient of expansion of steel tapes?
11.2 × 10−6 per ℃
What is the difference between the standard temperature and the actual temperature of the tape in the given example?
7ºC
What are the points at the beginning and end of the chain line called?
Survey stations
What is the line joining the main stations called?
Controlling line
What is the symbol used to denote main stations in chain surveying?
Δ
What is the purpose of main stations in chain surveying?
To mark the boundary of the survey
What is the symbol used to denote subsidiary stations in chain surveying?
Ο
Study Notes
Distance Measurement
- Distances obtained by pacing are sufficiently accurate for many purposes in surveying, engineering, geology, agriculture, forestry, and military field sketching.
Measuring Devices
- Passometer: a small instrument that counts the number of steps automatically in the case of longer distances.
- Odometer: converts the number of revolutions of a wheel of known circumference to a distance.
- Measuring Wheel: similar to an odometer, but more portable and self-contained, used to determine distances along irregular or curved lines and boundaries.
- Laser distance measurement: a method of measuring distances using laser technology.
Chaining Method
- Chaining method: an accurate and common method of measuring distances by using a chain or tape.
- Chains: prepared with several galvanized mild steel wires of different diameters used for linear distance measurement.
- Tape: a small tool used for measuring distances, prepared from different types of material and performed to various lengths (1m-100m).
- Types of tapes:
- Cloth or Linen tape: used for ordinary work, affected by moisture, and not strong.
- Metallic tape: linen tape reinforced with Brass or Copper wires, durable, and used for all survey works.
- Steel tape: not used in the field, used for standardizing chains and construction work.
- Invar tape: made of an alloy of steel and nickel, used at places where maximum precision is required.
Taping Accessories
- Inclinometer or clinometer: an instrument used for measuring angles of slope, elevation, or depression of an object with respect to gravity's direction.
Precautions in Using Instruments in Chaining
- Clean and dry chains and steel tapes after use in wet weather.
- Use a piece of colored cloth to enable arrows to be seen clearly on the field.
- Erect ranging rods as vertically as possible at the exact station point.
- Indicate the operating tension and temperature for which steel bands/tapes are graduated.
- Frequently test linen tapes for length and after repairs.
- Always keep tapes reeled up when not in use.
Cases for Measurement Distance by Tape
- Case A: length is less than the tape or chain length for horizontal ground length, easy to measure.
- Case B: length is more than the tape or chain length, requires ranging rod process.
Ranging Process
- Ranging process: the process of establishing intermediate points on a straight line between two endpoints.
- Direct ranging: done when the two ends of the survey lines are intervisible.
Mistakes and Errors in Chaining
- Error: the deviation of the measured value from the "exact" value of a quantity.
- Types of errors:
- Instrumental error: tape may differ in actual length from its nominal graduated length due to defects or repairs.
- Natural errors: the horizontal distance between end graduations of a tape varies due to temperature, wind, and weight.
- Personal errors: errors made by a surveyor or their equipment.
Errors in Chaining
- Errors in the length of tape or chain (Cumulative ±).
- Sag in the chain or tape (Cumulative +).
- Non-horizontally of the tape during measurement (Cumulative +).
- Bad ranging alignment (Cumulative +).
- Calculate the correct measured distance, assuming the error is evenly distributed throughout the tape.
Temperature Correction
- Temperature correction: tapes expand or contract due to temperature variation, causing systematic errors.
- Invar tape: a nickel-steel alloy with a very low coefficient of expansion, used to minimize temperature errors.
- Correction formula: Ct = ∝ × L × ∆T
Chain Survey
- Chain survey: suitable for surveying small areas with simple details and a fairly flat area, works on the principle of Chain Triangulation.
- Station In Chain Surveying: survey stations are the points at the beginning and the end of the chain line, including main stations and subsidiary or tie stations.
Lines In Chain Surveying
- Base Lines: the main and longest line, which passes approximately through the center of the field.
- Tie Or Subsidiary Lines: lines that join two tie stations, used to locate interior details, and also called auxiliary lines.
Learn about distance measurement techniques in engineering surveying, including the use of pacing and passometers. Important for surveying, engineering, geology, and more.
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