Equipment which traces the figure drawn on paper and measures the area. The equipment which traces a curve and measures the length is called curvimetre.
A black weight is set on the side of a figure to measure (the undersurface also has the needle so that it may not move), and a figure is traced with the index at the tip of an arm. The lens is attached to the white portion of an index and it can trace now correctly. There are the wheel and gear which rotate as an axis the arm to which the lens was attached in the portion of a joint, and it has become the structure which can read the move distance to the right-angled direction of an arm.

When area is before measured from a map in this type of planimeter, the numerical value which is different each time comes out, and it has been in difficulties. There is digital planimeter in office now. Although atmosphere where complicated calculation will surely be carried out in inside is created, seemingly, great calculation is omitted in practice.