A clinometer is an instrument used by surveyors and civil engineers to measure the angle of inclination of slopes and hills by referring to a plumb bob or spirit level. It is also used to measure the height of an object if the distance from the observer to the object is known. A clinometer is also called Abney level.
It consists of a sighting tube surmounted on a graduated vertical arc with an attached spirit level. A 45° mirror inside the tube enables the observer to see the bubbles at the same time the observer sights a point or a graduated rod with a horizontal wire. The surveyor first makes sure that the bubble is in the middle of the spirit level tube. This indicates that the clinometer is being held in a horizontal position. He or she looks through the eye hole and adjust the vertical arc to coincide with the sighted point. The vertical angle is indicated on the arc.
In the ‘plumb-bob’ clinometer, a plumb bob or a weight attached to a piece of string hangs from the sighting device. As the device is tilted upward to view the top of the hill, the string moves across a protractor like face and indicates the angle of inclination.
The clinometer is mainly used to measure the angles of slope. If set on a slope it can be used to give the angle of inclination of the surface. With the arc set at 0°, it can be used at a hand level.
