Person Identification using Shadow Analysis

We introduce a novel person identification method for a surveillance system of much wider area than conventional systems using CCTV cameras. In the proposed system, we install cameras to rooftops of buildings or a low altitude airship, and identify people by gait features extracted from shadows, which are projected on the ground by the sun in the daytime or lights in the evening. Figure 1 shows an image above a city; what appears to be the shape of a human body is in fact the shape of its shadow, a body projection. Shadows offer the connecting link between aerial observation and gait/biometrics/gesture and behavior classification. Since conventional systems extract gait features from actual body area, the correct classification ratio is reduced due to the lack of information of body area, in case that images are captured by overhead cameras. On the other hand, the proposed system enables to identify people by gait features which are extracted from shadows projected on the ground, even if images are captured by overhead cameras. In the proposed system, shadow areas projected on the ground are extracted automatically from captured images, and then analyze dynamics of shadow areas by the spherical harmonics. The following offers the summary of each process.