In 1818, Johann Martin Hermann, a Bavarian surveyor, built the first planimeter, a device that traces a curve with a needle point connected to a measuring wheel that converts the length of the tracing to the result of an integral function.

What is a planimeter used for?

A planimeter is a table-top instrument for measuring areas, usually the areas of irregular regions on a map or photograph.

Who invented digital planimeter?

The Swiss mathematician Jakob Amsler-Laffon built the first modern planimeter in 1854, the concept having been pioneered by Johann Martin Hermann in 1814.