TABLE 1. Summary of Sensing Intelligence Technologies Applications to Social Distancing.

Technology	Range	Accuracy	Cost	Privacy	Scalability	Indoor/Outdoor	Readily available devices
Ultrasound [7], [8], [10], [11]	Short, confined by walls	Less than 14 cm [8]	Low to Medium	Low [8] to High [9]	Medium	Indoor	Active Bat, Cricket systems
Inertial sensors [46], [95], [96], [98], [101], [105]	Not applicable	Less than 1 m [95]	Low	High	High	Both	Smartphone, body sensors networks
Visible light [15], [16], [18], [20], [21], [24]–[26]	Short	≤ 1 cm [25], ≤ 10 cm [16], [18], [26], ≤ 20 cm [19]	Low to Medium	High	High	Both	Smartphone, Smart Retail
Thermal [33], [35]–[37], [39]	IRP 10 m, THC a few km	IRP ≤ 0.125 mm [32], THC ≤ 0.9 m [38]	Medium to High	Low to High	Low to Medium	Both	Thermal Cameras