AirContour 1:11 0.2 0228m 0 阿 x0(m) 0 (a)3D contour (b)2D contour by PCA (c)2D contour with re- (d)2D contour with ro- versal tation Fig.11.Contour of character 'e'written with right hand,z-axis mean the projection of h,yh, Zh-axis,respectively 0 025 82 020 02 02 0.2 0(m (a)3D contour (b)2D contour by PCA (c)2D contour with re-(d)2D contour with ro- versal tation Fig.12.Contour of character'g'written with right hand,y-y-axis mean the projection of h,Uh,Zh,-Vh-axis,respectively 0.2 m xim) (a)3D contour (b)2D contour by PCA (c)2D contour with re- (d)2D contour with ro- versal tation Fig.13.Contour of character'd'written with right hand,yh -axis mean the projection of h,yh, Zh-axis,respectively 02 30-c 8 0 2m 02 xD(m) 02 02 0 02 (a)3D contour (b)2D contour by PCA (c)2D contour with re- (d)2D contour with ro- versal tation Fig.14.Contour of character 't'written with left hand,hyh,zh-axis mean the projection of xh,yh, zh-axis,respectively 4.2.1 Axis Projection Calculation.We project the Th-axis,yh-axis,zh-axis of human-frame into the principal plane,and then compare the length of the projected axis to determine the reference coordinate plane.According to Section 4.1,in the principal plane,the orthonormal ACM Trans.Sensor Netw.,Vol.1,No.1,Article 1.Publication date:January 2019.AirContour 1:11 (a) 3D contour (b) 2D contour by PCA (c) 2D contour with re￾versal (d) 2D contour with ro￾tation Fig. 11. Contour of character ‘e’ written with right hand, 𝑥 ′ ℎ, 𝑦 ′ ℎ, 𝑧 ′ ℎ-axis mean the projection of 𝑥ℎ, 𝑦ℎ, 𝑧ℎ-axis, respectively G, 2 (a) 3D contour (b) 2D contour by PCA (c) 2D contour with re￾versal (d) 2D contour with ro￾tation Fig. 12. Contour of character ‘g’ written with right hand, 𝑥 ′ ℎ, 𝑦 ′ ℎ, 𝑧 ′ ℎ, −𝑦 ′ ℎ-axis mean the projection of 𝑥ℎ, 𝑦ℎ, 𝑧ℎ, −𝑦ℎ-axis, respectively (a) 3D contour (b) 2D contour by PCA (c) 2D contour with re￾versal (d) 2D contour with ro￾tation Fig. 13. Contour of character ‘d’ written with right hand, 𝑥 ′ ℎ, 𝑦 ′ ℎ, 𝑧 ′ ℎ-axis mean the projection of 𝑥ℎ, 𝑦ℎ, 𝑧ℎ-axis, respectively (a) 3D contour (b) 2D contour by PCA (c) 2D contour with re￾versal (d) 2D contour with ro￾tation Fig. 14. Contour of character ‘t’ written with left hand, 𝑥 ′ ℎ, 𝑦 ′ ℎ, 𝑧 ′ ℎ-axis mean the projection of 𝑥ℎ, 𝑦ℎ, 𝑧ℎ-axis, respectively 4.2.1 Axis Projection Calculation. We project the 𝑥ℎ-axis, 𝑦ℎ-axis, 𝑧ℎ-axis of human-frame into the principal plane, and then compare the length of the projected axis to determine the reference coordinate plane. According to Section 4.1, in the principal plane, the orthonormal ACM Trans. Sensor Netw., Vol. 1, No. 1, Article 1. Publication date: January 2019