Dead reckoning

Dead-reckoning

Wind drift

CYA Coastal Navigation With Dead Reckoning 2

RCAF DR Nav Tools 1940

Dead reckoning is a process used in navigation to determine one's current position by using a previously determined position, or fix, and advancing that position based upon known or estimated speeds over elapsed time and course. The term "dead reckoning" is believed to have originated from the phrase "deduced reckoning," historically used in maritime navigation. In dead reckoning, the calculation of position is based on the physical laws of motion. This method is used to estimate the current position of a vehicle or vessel when external references are not available or reliable.

Overview

Dead reckoning involves the use of a compass for determining direction, a clock for time, and an instrument for measuring distance, such as a log in nautical applications or an Odometer in terrestrial navigation. The navigator uses these tools to calculate the current position based on the last known position, taking into account the speed, time elapsed, and direction of travel. This method is particularly useful when external references, such as GPS signals, are unavailable.

History

The practice of dead reckoning dates back to ancient times, when sailors navigated by the stars. As navigation technology evolved, so did the methods of dead reckoning. The invention of the magnetic compass in the 12th century and the development of more accurate timekeeping devices significantly improved the accuracy of dead reckoning calculations. In the age of exploration, dead reckoning was the primary method used by navigators to explore and map the world's oceans.

Techniques

Dead reckoning requires the navigator to record the course and speed of the vehicle at regular intervals. This information is then used to update the vehicle's position. The accuracy of dead reckoning can be affected by several factors, including the accuracy of the instruments used, the frequency of position updates, and environmental factors such as currents and winds.

Error Accumulation

One of the main limitations of dead reckoning is the accumulation of errors over time. Since each position update is based on the previous position, any errors in calculation will be carried forward into the next position estimate. This can lead to significant deviations from the actual position over long distances or periods.

Modern Applications

Despite the advent of satellite navigation systems, dead reckoning is still used today, particularly in environments where GPS signals are weak or unavailable. Examples include underwater navigation for submarines, indoor navigation for robots, and space navigation. In these contexts, dead reckoning is often used in conjunction with other navigation methods to improve accuracy.

See Also

• Navigation
• Celestial navigation
• Inertial navigation system
• Pilotage