Performance of commercial over-head camera sensors in recognizing patterns of two and three persons: A case study

Accurate visitor counting is needed in the research of people flows and people distributions. A case study about the performance of four commercial direction-sensitive over-head camera sensors (Axis and Biodata video camera counters, Sick time-of-flight camera, and Irisys thermographic people counter) in detecting patterns of two and three persons was carried out. Although all the tested sensors except Axis generally performed well with the patterns of two people, error rates of even over 20% were observed with the three-person patterns. Simultaneous false positive and false negative detections also occasionally speciously improved the counting results of Axis and Sick. Due to these flaws the accuracies of the sensors do not allow reliable people flow modeling or estimation of room occupancy levels, but is sufficient e.g. for measuring the order of magnitude of customer flows. However, as there are differences between separate counting sites, the results are only indicative in general.