Perception

AprilTag

AprilTag is a fiducial marker system from the APRIL laboratory at the University of Michigan, consisting of black-and-white square tags whose detection yields both a unique identifier and the full six-degree-of-freedom pose of the tag relative to a calibrated camera. Its detector is robust to rotation, lighting change, and partial occlusion, making it a standard tool for camera calibration, ground-truth tracking, and object or robot localization in labs.

Why it matters for physical AI

Fiducials provide cheap millimeter-level ground truth for evaluating learned policies and calibrating camera-to-robot transforms, and their gradual removal from a pipeline is a common milestone toward markerless deployed perception.