Dead reckoning needs a planned course

Dead reckoning is different from the casual idea of navigating by gut feeling. It starts with a known departure point and intended course, then estimates where the vessel should be after a period of travel. Wind and current can move a ship or aircraft sideways, while poor helm control can add further error even in calm water. A navigator compares the expected position with the observed one and corrects the course, sometimes deliberately steering into the current rather than pointing directly at the destination. Visible aids such as lighthouses make those corrections easier by showing how far the craft has drifted from its planned line.