We humans have many ways to find ourselves and discover our paths in life. For robots, odometry is the answer. Odometry describes calculations and solutions that help your robot know its location from its travel data in a process called “localization.” Localization is crucial to autonomous operation.

This odometry pod provides precision localization. Unlike encoder-equipped drive motors, whose rotation data doesn’t always reflect the actual motion of a chassis (see the "Why Odometry Pods?" box below), this odometry-dedicated solution is designed to reliably track the position of the chassis.

It functions as a “dead” 32mm diameter omni wheel integrated with a 2000 PPR encoder that, when powered via its JST PH connection, outputs the data of the dead wheel’s rotations against the ground as the chassis moves. Since the dead wheel doesn’t rotate otherwise, its rotation—and thus its data output—depends solely on the travel of the chassis.

Equipping an odometry pod to each side of a skid-steer chassis is a perfect way to track the chassis’ overall movement (which is facilitated by the combined input of its two sides). For a chassis with more complex maneuverability, such as a mecanum chassis, a third odometry pod is useful for tracking the additional degree of freedom.

The other half of odometry is the programming that reads the sensor’s input to derive your robot’s position and generate the path forward. To that end, there are plenty of FTC-focused resources for helping your software team get on-track with odometry! One great FIRST step you can take is this page in Game Manual 0.

Many motors (like Yellow Jacket Planetary Gear Motors!) have encoders that output data about their rotation. This can allow your robot to localize based on the rotations of its drive motors. However, your drive wheels may slip if your chassis accelerates too quickly, contacts an object (or another robot), or moves in an unpredictable way. This can cause a build-up of errors that result in your robot veering away from its target.

Fortunately, odometry pods, like the one featured here, allow you to track just the distance traveled instead of how far the motors have turned to get you there.

Dedicated odometric installations (like this one) often take the form of a "dead" (non-driven) wheel integrated with an encoder sensor as part of a "pod" package that tracks and relays information about the wheel's rotations as it travels against a surface. That's why they’re often known as "odometry pods," "dead wheels," or "tracking wheels.”