Davies, Charles, 1798-1876 · New York, Cincinnati [etc.] American book company · leaf 233
impossible to set the instrument over thecentre of such station. In such cases areduction to the centre is necessary. Let 0 be the position of the instrument,C the centre of a circular tower which marksthe station, and DCG the desired angle, Dbeing the right-hand object and G the left-hand one.… … SEC. T.] MAKING THE SURVEY. 227 Gy and estimating it towards the left, from 0^ to 300, as in thefigure. The angle 1 being exterior to the triangle DOl we haveI =z 0-{-a, and from the tnangle GIC we have /— C-\-(3,from which we deduce C=0-\-(a-fi) (1) We now need to determine the correction {a —…
Surveying
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