Importance

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Abstract

A hand-held scaler for a map or illustration uses a rotary element 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 miles on the map scale line; then the tip is run over the scale line (or a known distance between two points on the map). 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 shows the scaled distance (or a mathematical function of the distance). The rotary element can be a wheel in an axle or a sphere held in a retainer, like a ball-point pen ball. The sensor has a lamp and photocell to generate pulses by a pattern of reflective and non-reflective areas on the rotary element. The housing has switches for resetting, calibrating, and initializing, and a map-illuminating light. Battery power is cut off after long non-use.

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First Claim