A treatise on surveying, comprising the theory and the practice (1906)
Gillespie, William Mitchell, 1816-1868, Staley, Cady, 1840- · New York D. Appleton · leaf 331
lmost directly below the scale A A, lying in a parallel planeand fixed parallel to the horizontal limb of the instrument, is an-other scale B B. A triangular frame, or projection apparatus, supporting a vertical 320 TOPOGRArnr. scale E D, and a vernier c, rolls upon B B. After sighting to therod,… … read at the vernier c would be the corrected horizontal distance, andR sin. e read between the zeros of the verniers a and d would givethe difference in elevation. It is not as convenient to hold the rod normal to the line ofsight as to hold it vertically. If, however, the reading on B B(= Rcos.…
Surveying
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