Planimeter

A planimeter, also known as a platometer, is a measuring instrument used to determine the area of an arbitrary two-dimensional shape.Polar planimeterA planimeter (1908) measuring the indicated area by tracing its perimeterAmsler polar planimeterA linear planimeter. Wheels permit measurement of long areas without restriction.Three planimeters: digital, Prytz's (hatchet) and Amsler's (polar)Prytz planimeter with wheel at the leftLinear planimeterPolar planimeter A planimeter, also known as a platometer, is a measuring instrument used to determine the area of an arbitrary two-dimensional shape. There are several kinds of planimeters, but all operate in a similar way. The precise way in which they are constructed varies, with the main types of mechanical planimeter being polar, linear and Prytz or 'hatchet' planimeters. The Swiss mathematician Jakob Amsler-Laffon built the first modern planimeter in 1854, the concept having been pioneered by Johann Martin Hermann in 1814. Many developments followed Amsler's famous planimeter, including electronic versions.