is designed for measuring the length of curve lines on topographical maps, plans, and charts. The map measure (curvimeter) has a metric or dial in inches. If it has two dials the results of measuring can be obtained in centimeters or inches. Dials are different colors. The case is made of plastic. The device is packed in a special container.

A curvimeter, also called opisometer, meilograph, or map measurer consists of a toothed wheel of the known circumference on a handle. The wheel is placed in contact with the curved line to be measured and run along its length. By counting the number of teeth passing a mark on the handle while this is done, the length of the line can be ascertained:

line length = wheel circumference × teeth counted/teeth on wheel.

The instrument is most commonly used to measure the lengths of roads, rivers, and other line features on maps. Opisometers designed for this purpose provide scales reading the measured distance in kilometers and miles.
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