Graphometerとは 意味・読み方・使い方

The graphometer or semicircle is a surveying instrument used for angle measurements. It consists of a semicircular limb divided into 180 degrees and sometimes subdivided into minutes. The limb is subtended by the diameter with two sights at its ends. In the middle of the diameter a "box and needle" (a compass) is fixed. On the same middle the alidade with two other sights is fitted. The device is mounted on a staff via a ball and socket joint. In effect the device is a half-circumferentor. For convenience, sometimes another half-circle from 180 to 360 degrees may be graduated in another line on the limb.