A treatise on surveying ; in which the theory and practice are fully explained (1860)
Alsop, Samuel · Philadelphia, E. C. & J. Biddle & co. · leaf 128
Sec. II.] FIELD OPERATIONS. 125 Fig. 84. 216. (6.) When the Point is inaccessible. Erect a perpendicular atsome other point D (Fig. 84) ofthe line. Through F, a pointin this perpendicular, drawFH parallel to AB, (Art. 227.)Take FE = FD: range out EC,intersecting FH in G. MakeGH equal FG: then CHI… … (c.) If the line is inaccessible, trigonometrical methodsmust be employed. Problem 2. To let fall a perpendicular to a line from apoint without it. (a.) When the point and line are both accessible. 217. The methods in Arts. 91,92,93, may be adopted in this case;or in AB (Fig. 85) take any pointD,…
Surveying
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