Tracking Thread (SLAM)

• ORB-SLAM and PTAM both make use of this idea

On Keyframe Insertion

From PTAM:

• Keyframes are added whenever the following conditions are met: Tracking quality must be good; time since the last keyframe was added must exceed twenty frames.

From ORB SLAM: To insert a new keyframe all the following conditions must be met:

1. More than 20 frames must have passed from the last global relocalization.
2. Local mapping is idle, or more than 20 frames have passed from last keyframe insertion.
   • Idle here means it has run out of work to do, in which case we give it more work
3. Current frame tracks at least 50 points.
4. Current frame tracks less than 90% points than $K_{ref}$