Polar planimeter
Manufacturer
Allbrit
Date19th century
Object number00038293
NameSurveying instrument
MediumSteel, plastic
DimensionsOverall: 255 mm, 0.16 kg
ClassificationsTools and equipment
Credit LineANMM Collection Gift from Des Kerns
DescriptionThis polar planimeter is a type of mechanical analog computer. The planimeter integrates or calculates an area and records that area on a drum and disk as a tracing point moves over the boundary of the figure to be measured. Planimeters were used in engineering, naval and marine architecture until the mid-1980s.
HistoryPlanimeters were instruments used in the evaluation of plane areas of any shape from blueprints, maps, photographs, drawings, recorder diagrams, x-rays, etc. They were traditionally used by steam engineers, railway and naval architects and are still used today for different applications including cartography, hydrology, quantity surveying, road, dam and railway construction, ship design, mold patterning, mathematics, biology and medicine.
The planimeter was the first instrument used for measuring area by continuous integration or calculation, invented by the German engineer, J M Hermann, in 1814. The first complete planimeter was invented by Johannes Oppikofer and exhibited by him in Paris in 1836. A patent on a planimeter was granted in 1849 to Kasper Wettli and George Starke. The Swiss scientist Jacob Amsler invented the modern polar planimeter in 1854 which proved to be cheap, accurate and robust.
The Stanley family began making hardware in New Britain, Connecticut from 1831 on. They used a series of other names before they became the Stanley Works in 1852 and eventually the Stanley Rule and Level Company in 1857. Shortly after the turn of the century, the rapidly growing business established its first production facilities outside the US, including within the United Kingdom, where they produced the Allbrit polar planimeter.SignificancePolar planimeters were essential mathematical calculators and accumulators for the marine and naval engineer. The use of the planimeter saved time and money in the calculation of linear and plane space and in the calculation of volume for irregular shaped structures. They were superceded by CAD (Computer Assisted Drawing) and calculation programs in the mid-1980s.
