# Planimeter

## Definition - What does Planimeter mean?

Planimeter, also called as Platometer, is an instrument used to measure and determine the area of an arbitrary two-dimensional shape. There are five types of planimeters available however all operate in a similar way. They are:

• A Linear Planimeter
• Amsler Polar Planimeter
• Polar Planimeter
• Digital Planimeter
• Prytz’s Planimeter

The first modern planimeter was built in 1854 by Jakob Amsler Laffon, a Swiss mathematician.

## Petropedia explains Planimeter

The calculations for a regular shaped surface area are easy to perform as compared to the area calculations of an irregular shaped surface as it involves complex mathematical concepts and calculations. The area calculation of an irregular shaped surface becomes difficult as it makes use of area integration concepts. To overcome the complex and difficult process of integration of this irregular shaped area, a mechanical device called planimeter is used. Thus, Planimeter sometimes is also referred as an integrator tool that helps in converting irregular shaped geographical area into numerical values which can be analyzed and plotted on a sheet of paper. A Planimeter consists of:

• Two arms hinged at a point.
• Tracing arm with main scale.
• A vernier caliper scale
• Rotating disc and rotating drum with vernier scale.
• Pivot arm with a ball point at one end which can be fixed and a cylindrical weight with pin at the other end.
• Magnifying lens.

During the use of planimeter, the pivot arm is pivoted at one point on the irregular shape whereas the other arm called as the tracing arm is moved along the boundary of the irregular shape whose area needs to be determined. Calculations are read on the vernier scale and noted down for further analysis on a mathematical model.