# GeoAlign

Monocular 3D detectors have long recovered depth by substituting the 2D box height into the projection relation, and MonoPCA shows this returns the distance to the visible front surface rather than the object center, with an error that grows with object size. It keeps the measurable 2D box height and restores center depth through an orientation- and size-aware closed-form correction, while a teacher-student distillation strengthens size and orientation prediction; on the KITTI test set it reaches 20.55 moderate AP, 1.44 above MonoCoP.

Monocular 3D detectors have long recovered depth by substituting the 2D box height into the projection relation, and MonoPCA shows this returns the distance to the visible front surface rather than the object center, with an error that grows with object size. It keeps the measurable 2D box height and restores center depth through an orientation- and size-aware closed-form correction, while a teacher-student distillation strengthens size and orientation prediction; on the KITTI test set it reaches 20.55 moderate AP, 1.44 above MonoCoP.