Should be marked at both ends requires two people

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Unformatted text preview: uires two people, forward tapeperson, rear tapeperson) 2) Applying Tension : For accurate results, the tape must be straight and the two ends held at the same elevation. 3) 3) Plumbing : the tape is held above ground in a horizontal position. the tape is held above ground in horizontal position 4) Marking tape lengths : The marked point is checked by repeating the measurement until certainty of its correct location is assured. 5) Reading the tape : Add/Cut tape 6) Recording the distance Eo Y. D., Department of Technology Fusion, copyright® Direct Distance Surveying – Measuring on slanted ground • Stepping : divide the section which requires measurement in steps divide the section which requires measurement in steps and measure each division by laying the measuring tape horizontally wide steps sagging occurs with narrow steps the probability • With wide steps, sagging occurs, with narrow steps, the probability of error introduction increases • Convert to horizontal distance after measuring slope distance D = L cosθ D = L2 H 2 Eo Y. D., Department of Technology Fusion, copyright® Sources of Error in Taping Instrumental errors because of a defect in manufacture or repair or kinks. Natural errors because of the effects of temperature, wind and weight of tape. Personal errors • Elements of systematic Error in taping – – – – – – Erroneous tape length temperature Tension sag height slope Eo Y. D., Department of Technology Fusion, copyright® Incorrect Length of Tape Through extensive use, tapes do become kinked, stretched, and repaired. An error caused by incorrect length of tape occurs each time the tape is used If error caused by incorrect length of a tape occurs each time the tape is used. If the true length, known by standardization, is not exactly equal to its nominal value. ⎛ l − l′ ⎞ Cl = ⎜ ⎟Lm ⎝ l′ ⎠ L = Lm + C l Cl is the correction to be applied to the measured length of a line to obtain the true length, l the actual tape length l’ the nominal tape length, and Lm the measured length of line measured length of line. Eo Y. D., Department of Technology Fusion, copyright® Temperature Other than Standard Tapes may be expanded or contracted by temperature. The length can become something other than that specified. something other than that specified. Ct = α (T − Ts )Lm L = Lm + Ct Ct is the correction in the length of a line caused by nonstandard temperature, α the coefficient of thermal expansion and contraction of the tape, Ts the tape temperature at time of measurement, T the tape temperature when it has standard length, and Lm the measured length of line. Eo Y. D., Department of Technology Fusion, copyright® Inconsistent Pull • When a steel tape is pulled with a tension greater than its standard pull (the tension at which it was calibrated), the tape will stretch and become longer than its standard length. • Hooke’s Law : 변형하는 물체의 단면에 발생하는 응력(단위면적당 힘)...
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This note was uploaded on 09/27/2013 for the course AEROSPACE 202 taught by Professor Hsu during the Fall '13 term at ASU.

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