Define "dead reckoning" in navigation.

Dead reckoning in navigation refers to the method of calculating a vessel's current position by using its previously known position, along with speed, elapsed time, and course direction. This technique allows navigators to estimate their current location by taking into account how far they have traveled since their last known position. By accurately tracking speed and heading over time, a navigator can maintain an ongoing estimate of their location even when visibility is poor or when other navigational aids are unavailable.

This method is particularly important in situations where there are no visible landmarks or when satellite navigation systems are not accessible. It provides a foundational skill in navigation, ensuring that mariners can continue to navigate effectively and make informed decisions about their course and positioning. Thus, the correct choice encapsulates the essential elements of this navigational practice.