Elements of surveying and navigation : with a description of the instruments and the necessary tables (1847)
Davies, Charles, 1798-1876 · New York : A.S. Barnes & Co. · leaf 32
f the diameter AB, which indicates the centre ofthe protractor. To lay off an angle with a Protractor. Place the diameter AB on the line, so that the centre shallfall on the angular point. Then count the degrees containedin the given angle from A towards B, or from B towards Aand mark the extremity… … 25. The sector is an instrument generally made of ivory orbrass. It consists of two arms, or sides, which open by turn-ing round a joint at their common extremity. There are several scales laid down on the sector: those,however, which are chiefly used in drawing lines and angles,are, the scale of…
Surveying · Navigation
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