面めん積せき計けい

noun

planimeter

A measuring instrument used to determine the area of an arbitrary two-dimensional shape, typically by tracing its perimeter.

• 地ち図ず上じょうの湖みずうみの面めん積せきを面めん積せき計けいで測はかった。

  I measured the area of the lake on the map with a planimeter.