AprilGrid Calibration Targets: Coded AprilTag Grids for Kalibr Camera-IMU and Multi-Camera Calibration
An AprilGrid is a grid of individually coded AprilTags used by the Kalibr toolbox for multi-camera and camera-IMU calibration. Unique tag IDs let calibration succeed from partial views and remove the pose-flip ambiguity that affects symmetric checkerboards and circle grids. What it is, why Kalibr recommends it, the tag parameters that matter, how it differs from ChArUco, and how substrate sets the accuracy ceiling.