Design of a Visual System for Detecting Natural Events by the Use of an Independent Visual Estimate: A Human Fall Detector

We describe the development of a vision system to detect natural events in a low-resolution image stream. The work involved the assessment of algorithmic design decisions to maximise detection reliability. This assessment was carried out by comparing measures and estimates made by the system under development with measures obtained independently. We show that even when these independent measures are themselves noisy, their independence can serve to guide rational design decisions and allow performance estimates to be made. Although presented here for one particular system design, we believe that such an approach will be applicable to other situations when an image-based system is to be used in the analysis of natural scenes, in the absence of a precise ground truth.