Types of Measuring Tapes in Surveying:
Measuring tapes in surveying are critical tools used in surveying and civil engineering for measuring distances, heights, and angles. The type of measuring tape to use depends on the project’s requirements, the distance to be measured, and the necessary accuracy.
Here are the five most common types of measuring tapes used in surveying and civil engineering:
- Steel Tapes
- Cloth or Linen Tapes
- Glass-Fiber Tapes
- Metallic Tapes
- Invar Tapes
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Steel Tapes:
Steel tapes are the most commonly used measuring tapes in surveying and civil engineering due to their high accuracy and durability. They are made of steel and are available in lengths ranging from 30 to 100 meters, with a width of 13 to 25 millimeters. Steel tapes are calibrated to international standards, making them highly accurate and reliable. They are resistant to stretching, which means that they maintain their accuracy over long distances. Steel tapes are commonly used in large construction projects such as highways and bridges.
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Cloth or Linen Tapes:
Cloth or linen tapes are made of woven fabric and are used for measuring shorter distances up to 50 meters. They are lightweight, flexible, and easy to handle, making them ideal for use in situations where the tape needs to be bent around corners or obstacles. Cloth or linen tapes are calibrated to national standards, but their accuracy may be affected by stretching, which can occur over time. They are commonly used in surveying and mapping applications.
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Glass-Fiber Tapes:
Glass-fiber tapes are made of fiberglass and are commonly used for measuring distances ranging from 30 to 100 meters. They are lightweight, flexible, and easy to handle, making them ideal for use in difficult terrain or where steel tape would be too heavy to carry. Glass-fiber tapes are calibrated to international standards and are highly resistant to stretching, ensuring their accuracy over long distances. They are commonly used in surveying and engineering projects.
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Metallic Tapes:
Metallic tapes are made of aluminum or other metals and are commonly used for measuring shorter distances ranging from 3 to 30 meters. They are lightweight, durable, and easy to handle, making them ideal for use in situations where the tape needs to be carried around. Metallic tapes are calibrated to national standards but are less accurate than steel tapes and can also stretch over time. They are commonly used in construction and DIY projects.
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Invar Tapes:
Invar tapes are made of an alloy of iron and nickel and are commonly used for measuring precise distances. They are available in lengths ranging from 30 to 100 meters and are highly accurate, with a tolerance of less than 0.02 millimeters per meter. Invar tapes are calibrated to international standards and do not stretch, which ensures their accuracy over long distances. However, they are expensive and can be easily damaged, making them less suitable for use in harsh environments. They are commonly used in scientific and industrial applications.
Each type of measuring tape has unique features, advantages, and disadvantages. Steel tapes offer high accuracy and durability, while cloth or linen tapes and metallic tapes are lightweight and easy to handle. Glass-fiber tapes are ideal for use in difficult terrain, while invar tapes are used for measuring precise distances. Knowing the advantages and limitations of each type of measuring tape will help surveyors and civil engineers choose the right tool for the job.
Tape Corrections:
Tape correction is a critical process in surveying used to ensure that measurements made using a measuring tape are accurate. Measuring tapes can be affected by various environmental factors, which can cause errors in measurements. Tape correction involves applying a series of corrections to the measured values to account for these factors.
The Different Types Of Tape Corrections Used In Surveying.
- Correction for standardization
- Correction for slope
- Correction for pull
- Correction for temperature
- Correction for sag
- Correction for misalignment
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Correction for Standardization:
The first correction that needs to be made to a measured value is the correction for standardization. Measuring tapes are calibrated at a standard temperature, which is usually 20°C or 68°F. If the tape is used at a temperature other than the standard temperature, it will expand or contract, resulting in an error in the measurement. The formula for correction for standardization is:
Cs = Ls [(αt – αs) (t – ts)]
where Cs is the correction for standardization, Ls is the length of the tape at standard temperature, αt is the coefficient of thermal expansion of the tape at the current temperature, αs is the coefficient of thermal expansion of the tape at the standard temperature, t is the current temperature, and ts is the standard temperature.
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Correction for Slope:
The correction for slope is applied when measuring the distance between two points at different elevations. The formula for correction for slope is:
Cp = Lsin θ
where Cp is the correction for slope, L is the length of the tape, and θ is the angle of slope.
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Correction for Pull:
The correction for the pull is applied to account for the tension applied to the tape during measurement. If the tape is stretched, it will become longer, resulting in an error in the measurement. The formula for correction for pull is:
Cpl = T²/24PE
where Cpl is the correction for pull, T is the tension applied to the tape, P is the weight of the tape per unit length, and E is the modulus of elasticity of the tape.
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Correction for Temperature:
The correction for temperature is similar to the correction for standardization, but it applies to the temperature of the tape itself rather than the ambient temperature. The formula for correction for temperature is:
Ct = L [(αt – αs) (t – ts)]
where Ct is the correction for temperature, L is the length of the tape, αt is the coefficient of thermal expansion of the tape at the current temperature, αs is the coefficient of thermal expansion of the tape at the standard temperature, t is the current temperature, and ts is the standard temperature.
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Correction for Sag:
The correction for sag is applied to account for the curvature of the tape caused by its weight. The formula for correction for sag is:
Csag = 8wL³/27f²
where Csag is the correction for sag, w is the weight of the tape per unit length, L is the length of the tape, and f is the tension applied to the tape.
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Correction for Misalignment:
The correction for misalignment is applied when the tape is not held in a straight line between the two points being measured. The formula for correction for misalignment is:
Cm = (L² – d²)/2L
where Cm is the correction for misalignment, L is the length of the tape, and d is the horizontal distance between the two points being measured.
In conclusion, tape correction is a critical process in surveying used to ensure that measurements made using a measuring tape are accurate. The different types of tape corrections include correction for standardization, slope, pull, temperature, sag, and misalignment. Knowing how to calculate each correction