Dead reckoning is a navigation technique used to determine one’s current position by using a previously known position and calculating the course based on speed, time, and direction traveled. It does not rely on external references like landmarks or GNSS but instead uses measurements from an initial position, making it particularly useful in situations where no visual or satellite navigation is possible.
In the dead reckoning process, the navigator:
- Starts from a known position: this could be a location identified on a map, from a previous fix, or based on another reliable reference point.
- Keeps track of direction: the course is set using a compass, gyroscope, or other instruments to measure the bearing (direction).
- Measures speed: speed is typically recorded using a log (in maritime navigation), an airspeed indicator (in aviation), or a pace count (in land navigation).
- Calculates time: the time spent traveling is tracked accurately, as it is used to estimate how far one has moved.
- Applies the calculation: based on the direction, speed, and time, the navigator computes the new position, adjusting for any drift or variations along the way.
While dead reckoning is a reliable method for short distances, it tends to become less accurate over time due to errors that accumulate in direction, speed, and time estimates. As such, it’s often combined with other methods of navigation, like celestial navigation, landmarks, or GNSS, to improve accuracy and provide periodic fixes.
