Dead reckoning

Origin of: Dead reckoning

Dead reckoning

A method of estimating the position of a ship and navigating it based purely on calculation i.e. compass direction, speed and time elapsed since the last known position or fix, dates from the late 16th/early 17th century. Dead reckoning was used when the weather had closed in and no astronomical observations could be made. In those days, reckoning was a much more precise word meaning a calculation and dead was merely an intensifier meaning exact or precise. Obviously it was important to get it dead right. (See also Dead centre/certain/right/straight etc.)