Measuring the slope of a surface is important when constructing geometric figures. A bubble leveler is generally used to determine whether a surface is level or not: a bubble in a liquid-filled tube rests in the middle of the tube only if the surface it is sitting on is absolutely horizontal. However, on a slanted surface, the bubble moves away from the center. This kind of leveler has limited use, as it cannot tell the angle of the slant. When the shape of the leveler is elliptic, marks can be placed along the curved surface to show the angle of the slant, such as the elliptic leveler shown in Fig.
Fig 3.1. An Elliptic Leveler showing the position of the bubble on a horizontal surface
Although a tube shaped as any type of curve, the elliptic shape is ideal, as it allows for more divisions near the 0° mark and less as the angle measure increases.
Fig 3.2. An Elliptic Leveler showing a 10° inclination
Fig 3.3. The drop in the height of an elliptic curve with minor radius 1.5” and major radius 6” is shown; the drop is measured at every 5° of inclination