| 摘要 |
A hand-held scaler (1) for a map uses a rotary element (2) and an optical sensor at its tip to generate digital pulses when the tip is moved over a map surface. The pulses are counted by a microprocessor. Different pulse counts automatically scale distances on the map. The microprocessor is supplied with a number, e.g., the number of miles on the map scale line; then the tip is run over the scale line. The ratio of the number and the pulse count is used to scale arbitrary distances on the map by multiplying the tip pulses by the ratio. A readout (5) shows the scaled distance. The rotary element can be a wheel in an axle or a sphere held in a retainer. The sensor has reflective and non-reflective areas on the rotary element.
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