Pelorus

The Pelorus, or center line gyro repeater, is mounted on the flying bridge. It is a key instrument in piloting the ship close to shore and obtaining the true direction of nearby ships.

Mounted on a stand, the gyro compass can be fitted with an azimuth or "bearing circle" with site vanes that enable an observer to look through the vanes at a target and read its true direction. The more sophisticated "telescopic alidaide" was a similar device which contained a telescope to be used at long ranges.

The Officer of the Deck or Quartermasters used this device for staying on station in a convoy by observing the relative bearings of nearby ships. The device was also used in coastal piloting where the bearings or direction of known objects on shore were taken, plotted on a chart, thus creating a line of position. When two such bearings were taken, the place where the lines crossed indicated your ship's position. This was known as a "fix."