Gradskiva

Gradskiva, literally “degree disc” in Swedish, is a circular measuring instrument used to measure and lay out angles. It is widely used in drafting, surveying, navigation, astronomy, and education. A gradskiva consists of a circular disk, usually marked with angular graduations around its edge. Most commonly the scale is 0–360 degrees, sometimes with inner and outer scales or a vernier for finer resolution. The disc is mounted on a pivot or aligned with a straightedge; many versions include a locking screw to fix the orientation once an angle is set. Some gradskivor have a central hole for mounting on a stand or directly onto a drawing board.

Two broad forms exist: a standalone circular protractor-like disc, and a graduated dial used as part of a larger instrument, such as a compass or theodolite. In education, gradskiva is used to teach angle measurement and geometry. In drafting and engineering, it serves to transfer and measure angles on plans, to set slopes, or to transfer directions from a map or scale.

History: The concept of graduated circles and discs appears in various measuring instruments since the early modern period, evolving into compact hand-held gradskivor and digital variants in contemporary tools.

See also: protractor, graduated circle, dial indicator, vernier scale.