Bearing Rate (sometimes called rate of change of bearing before around 1913) is the measure of how quickly the compass bearing to an object changes over time. Generally, it is measured in degrees per minute, and the object in question is the target.
Bearing rate is a useful metric in fire control because bearing rate and range can be related to gun deflection. In some fire control mechanisms (such as on some Dreyer Fire Control Tables, a bearing rate might be entered into a bearing clock to help maintain an approximate bearing setting on appliances that use this, such as a dumaresq's dial plate.
Units of Measure
The British measured bearing rates in degrees per minute, left or right (in whole numbers). Other services probably did the same.
- Pollen Aim Correction System, Part I. p. 40.
- Dreyer, Frederic; Usborne, Cecil through Gunnery Branch, Admiralty. (1913). Pollen Aim Corrector System, Part I. Technical History and Technical Comparison with Commander F. C. Dreyer's Fire Control System. P. 1024. in Admiralty Library, Portsmouth.