Table 1. Features of nose in the depth image.

Classification	Feature
Adjacent pixel features	• The depth value of the upper, lower, left, and right pixels of the nose end point is larger than the nose end point.• There is a large difference in depth between the nose end point and the lower end.• The jaw located below the end of the nose is at the boundary of the face and neck, so the depth changes greatly.
Facial structural features	• The nose end point is located at the center of the width of the face• The upper and both sides of the face are background areas.• The bottom of the face is the object area.• The nose end point is located in the center of the face width.• The width of a typical human face ranges from 13cm to 22cm.