A planimeter is a drafting instrument used to measure the surface area of an arbitrary two dimentional shape. The precise way in which they are constructed varies, the main types of mechanical planimeter being Polar; Linear; and Prytz or "Hatchet" Planimeters. They rely on Green's theorem and were invented by the Swiss mathematician Jacob Amsler in 1854. Electronic versions also exist.

External links

• Whistleralley site (http://whistleralley.com/planimeter/planimeter.htm)
• Larry's Planimeter Platter (http://www.leinweb.com/snackbar/planimtr/)