A treatise on surveying ; in which the theory and practice are fully explained (1860)
Alsop, Samuel · Philadelphia, E. C. & J. Biddle & co. · leaf 132
cts his assistant, who is seen by reflec-tion through C, to place his rod in such a position that itsimage shall coincide with the hair across the opening B.HG- is then perpendicular to AF. To find the point in which the perpendicular from a dis-tant point will intersect AF, walk along the line,… … 226. To test the Accuracy of the Square. Erect aperpendicular with it, as above directed. Then sight alongthe perpendicular, and if the original line appears perpen-dicular, the instrument is correct; if it does not, the devia-tion will equal twice the error of the instrument. Set apole in the true…
Surveying
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