How does dead reckoning estimate a craft’s position?

Dead reckoning is a method of determining a craft’s position by using a known starting point and calculating subsequent movement based on the record of courses steered or flown, distance traveled (estimated from velocity), and known or estimated drift.1

To estimate position, a navigator tracks the craft's progress over time. In marine navigation, this involves using a compass to determine the course and a log to measure distance, with adjustments made for ocean current or tidal drift. For aircraft, navigators must account for the wind by calculating the vector sum of the craft’s air velocity and the wind velocity to determine the true ground speed and track.2

Because errors in dead reckoning accumulate over time, navigators periodically use celestial navigation or other landmarks to obtain a "fix," which serves as a new, accurate starting point for further calculations. Modern systems often automate this process using inertial guidance systems or Kalman filtering to integrate various navigation data into a reliable estimate.12