A treatise on surveying, comprising the theory and the practice ; (1887)
Gillespie, W. M. (William Mitchell), 1816-1868, Staley, Cady, 1840- [from old catalog] ed · New York, D. Appleton and company · leaf 404
es.For short distances, curvature and refractionmay be neglected. Thus, if the heightof a wall, house, tree, etc., be desired,note the point where the horizontalline strikes the wall, etc., and add itsheight above the ground to that calcu-lated by the formula :BC = AC. tang. B A C. . . . [1.] 579.… … 390 LEVELING. Fig. 424. B. Foe Geeatee Distances. 580. Correction for Curvature. A C is the line of apparentlevel, as given by the instrument, and A 0is the line of true level. Galling the angleA 0 B = 90° (which it is approximately formoderately great distances), formula [1] givesB C as the height…
Surveying
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