Leonardo da Vinci designed an inclinometer to determine the inclination of a surface.
An inclinometer, also called a clinometer in many contexts, measures the angle of a slope relative to a reference direction. Leonardo’s studies of mechanics and geometry included instruments for measuring angles, slopes, and the behavior of machines. Such measurements were useful in surveying, architecture, military engineering, and waterworks.
Leonardo’s instrument ideas were part of a wider Renaissance interest in turning observations into quantitative information. Rather than relying only on visual judgment, an engineer could use a weighted indicator or comparable mechanism to read an angle.
The term is broader than one single historical drawing, and later inclinometers took many forms. A modern electronic inclinometer may use accelerometers, while older versions used pendulums, levels, or graduated scales. The key fact is the measurement function: an inclinometer measures inclination, not altitude, air pressure, or distance traveled.