Figure 7From: Probing crowd density through smartphones in city-scale mass gatheringsUser density (GPS) vs. crowd density (CCTV). (a) Scatter plot of ( ρ User , ρ Crowd )-tuples. This data was obtained throughout the whole event at three distinct locations. The green fit line indicates the linear regression. (b) influence of the kernel radius R of Equation 1 on the correlation coefficient r of the linear regression.Back to article page