| 摘要 |
An instrument for taking bearings of objects, particularly for use in coastal navigation, has a main body with one or two arms pivoted to the body. A first object is sighted through the main body, over the top of a plane mirror. Once a zero line of the main body is lined up on one object, the or one of the pivoted arms is swung out from the main body to point at a second object. The arm which is swung out is coupled to a second mirror arranged in the main body, so that as the arm is swung out, the second mirror rotates in the same direction and through half the angle that the arm turns through. Light rays from the second object are reflected from this second mirror to the first mirror in the main body, and then back to the eye of the observer. When the instrument is correctly adjusted, the observer will see the first object over the top of the first mirror and the second object in the first mirror, just below the first object. In this position, the angle between the main body and the arm that has been swung out is equal to the bearing between the two objects, and this bearing can be plotted directly on a chart, or made use of in other ways.
|
