What Is Dead Reckoning? How Robots Estimate Their Position.

What Is Dead Reckoning?

Dead reckoning is a navigation method that estimates a machine's current position by starting from a known location and calculating how far and in what direction it has moved.

The technique is used in robotics, vehicles, aircraft, and other navigation systems.

For example, a warehouse robot can estimate its movement using wheel rotations and information about its direction.

However, small measurement errors accumulate as movement continues, making dead reckoning less reliable over long periods without correction.

Key Takeaways

• Dead reckoning estimates position using a known starting point and subsequent measurements of motion.
• Robots commonly use wheel encoders, inertial sensors, and other motion information for this purpose.
• Position errors accumulate over time, so dead reckoning is often combined with external references or localization methods.

How Does Dead Reckoning Work?

Imagine a mobile robot beginning at a known point in a warehouse.

The robot moves forward five meters, turns right, and travels another three meters.

If the robot knows the distance and direction of each movement, it can calculate an estimated new position.

Wheel encoders may measure wheel rotation, while a gyroscope can provide information about rotational movement.

The robot's software combines these measurements to update its estimated location.

This process can continue even when the robot does not have an external positioning reference.

Why Does Dead Reckoning Accumulate Errors?

The calculations depend on imperfect measurements.

A wheel may slip slightly on the floor.

Its effective rolling diameter may differ from the value assumed by the software.

A gyroscope may introduce small measurement errors.

Each new position estimate is calculated using earlier estimates.

As a result, small inaccuracies can accumulate.

After enough movement, the robot's estimated position may differ significantly from its actual location.

This phenomenon is commonly called drift.

Dead Reckoning vs. SLAM

Dead reckoning estimates movement relative to a starting position.

Simultaneous localization and mapping, or SLAM, uses sensor observations to estimate a robot's position while building or updating a representation of its environment.

SLAM can help correct accumulated movement errors by recognizing environmental features.

For example, a robot may use wheel odometry for continuous movement estimates and LiDAR-based localization to correct its position when it recognizes nearby structures.

The approaches often work together.

Frequently Asked Questions

Can dead reckoning work without GPS?

Yes. It relies on movement measurements rather than requiring a continuous external positioning signal.

Is dead reckoning accurate enough for autonomous robots?

It can be useful for short-term movement estimates, but many applications require additional methods to correct accumulated errors.

The Bottom Line

Dead reckoning allows robots to track estimated movement from a known position. It provides continuous navigation information, but accumulated errors make additional localization references important for reliable long-term operation.