Elements of surveying and levelling; with descriptions of the instruments and the necessary tables (1870)
Davies, Charles, 1798-1876 · New York and Chicago, A. S. Barnes & Company · leaf 91
to thesum of the angles A andADB, it follows that, theangle ADB is equal to the difference of the angles of elevation at A and B. Hence, wecan find all the parts of the triangle ADB. Having found DB,and knowing the angle DBC, we can find the altitude DC. This method supposes that the stations A and… … SEC. I.] HEIGHTS AND DISTANCES. 89 AB = 975 yards, A = 15° oG, and DBC = 27° 29;required the altitude DC. First: ADB = BBC - A = 27° 29 - 15° 36 = 11° 53. In the triangle ADB, to find BD = c. sin D : sin ^ : : AB : DB; hence,(a. c.) log sin D (11° 53) .... 0.686302log sin A (15° 36) ....…
Surveying
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