A treatise on surveying ; in which the theory and practice are fully explained (1860)
Alsop, Samuel · Philadelphia, E. C. & J. Biddle & co. · leaf 133
an inaccessible line, twopoints of which are visible. 228. Let AB (Fig. 92) be thestraight line, and C the givenpoint. Run the line CD per-pendicular to AB, by Art. 220;and from C set out CE perpen-dicular to CD. It will be theparallel required. Problem 3.— To draw a parallel to a given line… … Sec. III.] OBSTACLES IN RUNNING AND MEASURING LINES. 131 tersecting DE in E. Measure AB and DE. Run through any point in AB the line BFG, intersecting DE in F. DE.BFMake FG = —-—=—3 and CG will be parallel to AB.AB — DE DE . BF For, since FG = —-——- >wehaveAB-DE:DE::BF:FG.AB —DE Whence AB : DE…
Surveying
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