A treatise on levelling, topography, and higher surveying (1876)
Gillespie, W. M. (William Mitchell), 1816-1868, Staley, Cady, b. 1840, ed · New York, D. Appleton and company · leaf 177
Boston hi o … THE FIELD-WORK. 157 Fig. 200. (240.) Signals. They must be high, conspicuous, and somade that the instrument can be placed precisely under them. Three or four timbers framed into apyramid, as in Fig. 200, with a long mastprojecting above, fulfil the first and lastconditions. The mast may be made…
Surveying
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