Chord scale

In surveying, a chord scale is a type of scale used on a plan or map to measure linear distances. It is a straight ruler with a scale marked in units of length (such as meters or feet), used to measure distances along a curved line by laying it end-to-end along the curve. The name "chord scale" comes from the fact that it acts like a chord of a circle, connecting two points along a curve. Chord scales are often used in land surveying, topographic mapping, and other similar applications where precise measurements of curved or irregularly shaped features are required.