Planimeters are used to measure areas on maps of any kind and scale, as well as plans, blueprints, or any scale drawing or plan. They are often used by surveyors, foresters, geologists, geographers, engineers, and architects.
Some models have adjustable length pole and tracer arms, while others are fixed length.
All have a reset which returns the measuring dial and vernier scale to zero before the next use. Digital planimeters are computerized. They give a direct reading of the area traced as square inches or centimeters, with some reading directly in any unit of area including acres, square meters, square kilometers, etc. The most advanced units will also store data for downloading into a personal computer. Most digital planimeters have various memory functions which enable you to add areas, accumulate measurements, and average multiple measurements.