What is dead reckoning used for in navigation?

Dead reckoning is a navigation method used to determine a vessel's current position based on previously known positions, factoring in the vessel's heading, speed, and the time elapsed since the last known position. This technique involves plotting a course using the course direction and distance traveled over a period of time to estimate where the vessel is located at that moment.

By applying dead reckoning, sailors can create a continuous estimation of their position, which is particularly useful when other means of position determination, such as GPS or visual landmarks, are not available. It provides a reliable method for tracking movement over water while taking into account the vessel's average speed and any changes in heading due to wind or water currents.

In contrast, the other choices pertain to different navigation methods and calculations. Finding the nearest land point involves using charts and possibly radar or visual sighting, which are distinct from the dead reckoning process. Calculating tides and currents requires knowledge of local tide tables and current patterns, rather than relying solely on heading and speed. Measuring distance by celestial bodies is an entirely different navigation method, known as celestial navigation, where the positions of stars or other celestial bodies are used to determine one’s location. This method typically does not overlap with the principles of dead reckoning