Body and Head Orientation Estimation from Low-Resolution Point Clouds in Surveillance Settings
This work addresses privacy-preserving behavioral analysis in surveillance and clinical settings, though it represents an incremental advancement by adapting existing methods to low-resolution data.
The researchers tackled the problem of estimating body and head orientations from low-resolution LiDAR point clouds in surveillance settings, achieving mean absolute errors of 5.2 degrees for body orientation and 13.7 degrees for head orientation. They demonstrated the system's application by showing that autistic individuals exhibit significantly different attention distribution patterns in conversations compared to neurotypical individuals.
We propose a system that estimates people's body and head orientations using low-resolution point cloud data from two LiDAR sensors. Our models make accurate estimations in real-world conversation settings where subjects move naturally with varying head and body poses, while seated around a table. The body orientation estimation model uses ellipse fitting while the head orientation estimation model combines geometric feature extraction with an ensemble of neural network regressors. Our models achieve a mean absolute estimation error of 5.2 degrees for body orientation and 13.7 degrees for head orientation. Compared to other body/head orientation estimation systems that use RGB cameras, our proposed system uses LiDAR sensors to preserve user privacy, while achieving comparable accuracy. Unlike other body/head orientation estimation systems, our sensors do not require a specified close-range placement in front of the subject, enabling estimation from a surveillance viewpoint which produces low-resolution data. This work is the first to attempt head orientation estimation using point clouds in a low-resolution surveillance setting. We compare our model to two state-of-the-art head orientation estimation models that are designed for high-resolution point clouds, which yield higher estimation errors on our low-resolution dataset. We also present an application of head orientation estimation by quantifying behavioral differences between neurotypical and autistic individuals in triadic (three-way) conversations. Significance tests show that autistic individuals display significantly different behavior compared to neurotypical individuals in distributing attention between conversational parties, suggesting that the approach could be a component of a behavioral analysis or coaching system.