Elevation

In gunnery, is one of the elements of pointing, being the movement of the axis of a piece in a vertical plane as distinguished from direction or its movement horizontally. The elevation is usually positive,—that is, the gun is pointed above the horizontal. When it is pointed below, it is said to be depre ed. The word is also used to expre degree, or as a synonym for angle of elevation . The sights or elevating apparatus of guns are graduated on the theory that the object is in the horizontal plane of the piece, or that the line of sight is horizontal, which is not always the case in practice. When the elevation is determined by sights the angle of elevation is the angle between the line of sight and the axis of the piece, when these lines are in the same vertical plane,—or the angle between the line of sight and a plane containing the axis of the piece and a horizontal line intersecting it at right angles, when they are not. The graduations of tangent scales and fixed breech-sights give this angle in degrees. The graduation of the pendulum hau e gives the angle correctly only when the line of sight is horizontal. When the elevation is given by elevating arcs or gunner’s quadrant, the angle of elevation becomes the angle of fire, or the angle which the axis of the piece makes with the horizontal. Elevation is nece ary to overcome the effect of gravity on the projectile. The degree of elevation increases with the range. In vacuo the elevation corresponding to the maximum range is 45°. In the air the angle of maximum range diminishes with the velocity and increases with diameter and density of the ball. It is greater in mortars than in howitzers, and greater in howitzers than in guns. In mortars it approximates to 42°; in guns it is about 37°.