Davies, Charles, 1798-1876 · New York, Cincinnati [etc.] American book company · leaf 185
178 ELEMEIfTS OF SURVEYmG. [book IV. Note 2.—It should be remembered that the vertical distance,which is obtained by the calculation, is estimated from a hori-zontal line passing through the eye, at the time of observation.Hence, the height of the instrument is to be added, in order toobtain the… … 201. When the nature of the ground will admit of it,measure a base-line AB, in the direction of the object D, Thenmeasure, with the instrument, the angles of elevation at Aand B. Then, since the out-ward angle BBC is equalto the sum of the anglesA and ADB, it followsthat the angle ABB isequal to…
Surveying
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