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 32
er AB, which indicates the centre ofthe protractor. IV. To lay ofif an angle with a Protractor. 30. Place the diameter AB on the line, so that the centreshall fall on the angular point. Then count the degrees con-tained in the given angle, from A toward B, or from B towardAy and mark the extremity… … 31. The sector is an instrument generally made of ivory orIrass. It consists of two arms, or sides, which open, by turninground a joint, at their common extremity. There are several scales laid down on the sector: those, how-ever, which are chiefly used in drawing lines and angles, are,the scale of…
Surveying
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