lecture4_new - Lecture 4 Distance Measurement Measurement...

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Lecture 4. istance Measurement Distance Measurement Eo, Yang Dam Eo Y. D., Department of Technology Fusion, copyright®
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Definition of Distance In traditional ground surveys, even though many angles may be read, the length of at least one line must be observed to supplement the angles in locating points. In plane surveying, the distance between two points means the horizontal distance. Distance between two positions on reference ellipsoid When the radius of the reference surface is 6370km, the arc distance of circle that transits positions on this spherical surface Distance measured horizontally Eo Y. D., Department of Technology Fusion, copyright®
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Summary Traditional Distance Measurement . acing 1. Pacing 2. Odometer readings 3. Optical rangefinders 4. Tacheometry (stadia) 5. Subtense bars i Electronic Distance Measurement (EDM) 6. Taping () Satellite-supported Global Navigation Satellite Systems (GNSS) ost otably ecause f eir nge curacy ficiency : most notably because of their range, accuracy, efficiency Photogrammetry Eo Y. D., Department of Technology Fusion, copyright®
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Methods for Making Linear Measurement Pacing 9 When performed on horizontal or uniformly sloping land, pacing can be performed at an accuracy level of 1/50~1/100. 9 1 pace = 0.75m (may different in person) Odometer 9 Converts the number of revolutions of a wheel of known circumference to a distance. 9 Accuracy of approximately 1/200 Optical Rangefinders 9 Same principle as rangefinders on single-lens reflex cameras. 9 Object distance f 2 where focal length f and image distance f 1 are known. Tacheometry 9 Stadia is a surveying method used to quickly determine the horizontal distance to and elevation of a point. 9 The distance from telescope to rod is found by proportional relationship in similar triangles. Eo Y. D., Department of Technology Fusion, copyright®
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Tapes for Distance Surveying Common Measuring tape Used for simple measurement Easy and convenient to handle, yet its elasticity to humidity and tension make it inappropriate for accurate distance measurement Relative accuracy 1/3,000~1/5,000 Steel tape p Used for accurate distance measurement or for baseline surveying of low level triangulation Since it is used in precise measurements, corrections for temperature and tension are necessary Relative accuracy 1/10,000~1/30,000 Invar tape ighly precise measuring tape with low rate of expansion to heat and with extremely Highly precise measuring tape with low rate of expansion to heat and with extremely little elasticity to tension Used for highly precise measurements such as baseline surveying in triangulation Relative Accuracy 1/100,000~1/1,000,000 Fiber Glass tape Low elasticity to humidity, however, has high elasticity caused by tension compared to steel tape elative Accuracy 1/3 000~1/10 000 Eo Y. D., Department of Technology Fusion, copyright® Relative Accuracy 1/3,000 1/10,000
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Taping on Level Ground 1) Lining In : the line to be measured should be marked at both ends.
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lecture4_new - Lecture 4 Distance Measurement Measurement...

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