Planimeters

Planimeters

A planimeter is a mechanical device used to measure the area of an irregularly shaped two-dimensional object. It was invented by the Swedish mathematician and inventor Jonas Ferdinand Gabriel Lippmann in 1875. The planimeter consists of a tracing point, a measuring wheel, and an indicator dial. The tracing point is used to trace the perimeter of the object to be measured, while the measuring wheel rolls along the perimeter and records the distance traveled. The indicator dial displays the area of the object in square units. The planimeter is commonly used in fields such as surveying, engineering, and cartography, where accurate measurements of irregularly shaped objects are required. It is particularly useful in measuring the area of land parcels, lakes, and rivers. The planimeter can also be used to measure the area of irregularly shaped objects in photographs or maps. The accuracy of a planimeter depends on the precision of its components and the skill of the operator. The measuring wheel must be calibrated to ensure accurate measurements, and the tracing point must be held steady and moved along the perimeter at a constant speed. The planimeter is also sensitive to errors caused by variations in the surface of the object being measured. Despite the advent of digital measuring devices, the planimeter remains a valuable tool in certain applications, particularly in situations where digital devices may be impractical or unavailable.

Jonas Ferdinand Gabriel Lippmann, measuring wheel, surveying, engineering, cartography

— Patrick Lewis