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Unformatted text preview: 은 탄 성계수와 변형률(늘어난 길이/원래 길이)의 곱과 같다. CP = (P − Po ) L AE L = Lm + C P m Cp is the total elongation in tape length due to pull, P the pull applied to the tape at the time of the observation, P0 the standard pull for the tape, A the cross sectional area of the tape, E the modulus of elasticity of steel, and Lm the measured length of line. Eo Y. D., Department of Technology Fusion, copyright® Sag Corrections A steel tape not supported along its entire length sags in the form of a catenary curve. Because of sag, the horizontal distance (chord length) is less than the graduated distance between tape ends. CS = − w 2 Lm 3 24 P 2 L = Lm + C S Cs is the correction for sag (difference between length of curved tape and straight line from one support to the next), Lm the unsupported length of the tape, w the weight of the tape per foot of length, and P the pull on the tape. Eo Y. D., Department of Technology Fusion, copyright® Height Corrections • Corrections on height – Convert the distance measured at a certain height to the the distance measured at certain height to the distance on reference ellipsoid (mean sea-level) (Example) The length of baseline Lm R L= R+h located at the height of 326.42m is 326 measured to be 500m. Convert to the h : 측정시 length on reference mean sea length on reference mean sea-level. 표고 R : 지구의 평균곡률반경 The mean radius of earth is assumed 6367Km 6367Km. Eo Y. D., Department of Technology Fusion, copyright® Slope Corrections • • Since survey measurements are normally shown on a plane, if the measurements were taken on slope they then must be converted to measurements were taken on a slope, they then must be converted to their horizontal equivalents before they can be plotted. To convert slope distances, either the slope angle or the vertical distance distance must also be known. also be kno 2 L = Lm − H 2 H : 두 지점간의 높이차 Eo Y. D., Department of Technology Fusion, copyright® Measurement of Baseline • Precise distance measurement Steel tape is used for measurements not requiring high precision, Invar hi tape (short distance) or Electromagnetic Distance Measurement (EDM) for the ones that need high accuracy • Now EDM instruments have made it possible to obtain accurate distance measurements rapidly and easily. • Given a line of sight, long or short lengths can be measured over bodies of water, busy freeways, or terrain that is inaccessible for taping taping. • The temperature and tension at the time of inspection are recorded for later use in corrections after the measurement Eo Y. D., Department of Technology Fusion, copyright® Electronic Distance Measurement(1) • The distance between two points can be measured by multiplying the number of wavelengths it took to move between the two points with explicit electromagnetic wavelengths (round-trip distance) • Geodimeter (geodetic distance meter, 1948) : this transmitted visibl...
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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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