# Human Height Estimation by Color Deep Learning and Depth 3D Conversion
## 4 Experiment Results  
Intel Realsense D435 is used as a depth camera for the experiments of the proposed method. A focal length \(f\) and a frame rate of the depth camera are 325.8 mm and 30 Hz, respectively. The resolutions of depth video are specified as \(640\times 480\). The threshold \(T_{b}\) for (1) and \(T_{o}\) for (6) are set to 100 and 50, respectively. The parameter \(\gamma\) in (9) is 4000, which means \(r\) is 2 when \(d_{h}\) is 2000 mm. Figures 9 and 10 show the extractions of the human body region through by mask R-CNN and by the background depth image, respectively. Both methods of the human body region extraction accurately extract the human body region at not only a standing state, but also a walking state. In addition, the human body region is accurately extracted regardless of the states of the human body. In Figure 9, areas painted in green and red are the human body and human head regions, respectively. The human head regions are accurately found even though the position of the hand is above the head. The human body region extraction by the background depth image extracts larger regions than by mask R-CNN, so some part of the background is included in the human body region. In addition, the bottom area of the human body is not included in the human body region because the depth values of these area are similar to the depth value of the ground. Figure 9: Extraction of human body region by mask R-CNN. (**a**) Standing toward front; (**b**) standing backward; (**c**) standing sideways; (**d**) walking toward camera; (**e**) walking opposite to camera; (**f**) lateral walking, (**g**) standing toward front and waving hand; (**h**) standing backward and waving hand. Figure 11 shows the correction of human height by (12) when the body region is extracted by mask R-CNN. The distributions of the estimated human height are large because of the noises of the depth frame when the correction of human height is not applied. After applying the correction of the human-height estimation by (12), the human heights are estimated as certain heights after about 20 frames. Figure 12 shows the result of the human-height estimation depending on the methods of the human body region extraction. The actual height of a person is 177 cm. In the human body region extraction through the background depth image, first 50 frames are accumulated to generate the background depth image. The human body keeps at a distance of 3.5 m from the camera. The body height is estimated as 176.2 cm when the human body region is extracted by mask R-CNN. The body height is estimated as 172.9 cm when the human body region is extracted by the background depth image. Figure 11: Results of height estimation after correction through cumulative average for each three persons. Figure 10: Extraction of human body region by background depth image. (**a**) Standing toward front; (**b**) standing backward; (**c**) standing sideways; (**d**) walking toward camera; (**e**) walking opposite to camera; (**f**) lateral walking. Figure 13 shows the result of the human-height estimation according to the distance between human body and the camera. The actual height of a person is 182 cm. The distances from the camera are 2.5 m, 3 m, 3.5 m, 4 m and 4.5 m. The averages of the human heights are estimated as 181.5 cm, 181.1 cm, 181.2 cm, 179.7 cm and 179.8 cm when the distances are 2.5 m, 3 m, 3.5 m, 4 m and 4.5 m, respectively. Figure 14 shows the result of the human-height estimation when a person whose height is 180 cm is standing, walking toward the camera and lateral walking. Human body keeps at a distance of 2.5 m from the camera when the human is standing and lateral walking. When the human is walking toward the camera, the distance from the camera is in range of 2.5 m to 4 m. In the standing state, the human height is estimated as 178.9 m. The human height is 177.1 cm and 174.9 cm in the lateral walking and the walking toward the camera, respectively. The magnitude of the estimated error in the lateral walking state is similar to in the standing state.