What is the primary purpose of dead reckoning in navigation?

Dead reckoning is a navigation technique used primarily to estimate a vessel's current position based on its last known position, course, and speed over a given period. The method involves projecting the vessel's journey forward, accounting for the direction it was heading and the speed at which it was moving. By doing this, navigators can create a path or projection of where they believe the vessel is currently located, facilitating easier course adjustments and planning.

This technique relies on the assumption that the course and speed have remained constant, making it essential for maintaining an updated position while at sea, particularly when more precise methods of navigation, such as celestial observations or GPS, are not available. It is a fundamental skill for mariners to ensure safe and accurate navigation.