1. The images show the principles of a linear and a polar planimeter . 2. A planimeter is a device which does integrals, using distance as the analog quantity. 3. The polar planimeter is restricted by design to measuring areas within limits determined by its size and geometry. 4. In 1893 Durand published a paper mathematically describing a radial planimeter for averaging values plotted in polar coordinates. 5. The pointer M at one end of the planimeter follows the contour C of the surface S to be measured. 6. When the planimeter 's measuring wheel moves perpendicular to its axis, it rolls, and this movement is recorded. 7. The working of the linear planimeter may be explained by measuring the area of a rectangle ABCD ( see image ). 8. The same figure was also used in the old town plan of Quezon and was validated by using a digital planimeter . 9. Originally a radial planimeter was of academic interest only, but ten years later clock driven recording instruments started being used. 10. In 1887 Petersen had constructed another model; a planimeter which was presented to the Royal Danish Academy of Science and Letters. 
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