loop closure

Recognizing that a camera has returned to an already-mapped place, and using that fact to correct drift across the whole path.

Loop closure detects that a moving camera has revisited a previously mapped location, supplying a new constraint -- the pose right now and the pose from that earlier visit are the same physical place -- that no purely sequential frame-to-frame link could provide. Re-optimizing the pose graph with this constraint added redistributes accumulated drift across the entire loop, not just its two endpoints.

Examples

A warehouse robot that recognizes it has circled back to a shelf it mapped ten minutes ago uses that loop closure to straighten out its entire estimated path, not just its current position.