An Objective Method for Pedestrian Occlusion Level Classification
This addresses the need for reliable ground truth annotation in safety-critical autonomous vehicle systems, though it is incremental as it improves existing annotation practices rather than introducing a new detection paradigm.
The paper tackles the problem of inconsistent and subjective occlusion level annotation in pedestrian detection benchmarks by proposing a novel, objective method for classification based on visible keypoints and 2D body surface area estimation, demonstrating effectiveness across various occlusion types including challenging edge cases.
Pedestrian detection is among the most safety-critical features of driver assistance systems for autonomous vehicles. One of the most complex detection challenges is that of partial occlusion, where a target object is only partially available to the sensor due to obstruction by another foreground object. A number of current pedestrian detection benchmarks provide annotation for partial occlusion to assess algorithm performance in these scenarios, however each benchmark varies greatly in their definition of the occurrence and severity of occlusion. In addition, current occlusion level annotation methods contain a high degree of subjectivity by the human annotator. This can lead to inaccurate or inconsistent reporting of an algorithm's detection performance for partially occluded pedestrians, depending on which benchmark is used. This research presents a novel, objective method for pedestrian occlusion level classification for ground truth annotation. Occlusion level classification is achieved through the identification of visible pedestrian keypoints and through the use of a novel, effective method of 2D body surface area estimation. Experimental results demonstrate that the proposed method reflects the pixel-wise occlusion level of pedestrians in images and is effective for all forms of occlusion, including challenging edge cases such as self-occlusion, truncation and inter-occluding pedestrians.