The system is composed of three sensor nodes
equipped with PIR sensors having modified Fresnel lenses to
narrow their field of views and a coordinator node, and located
along a wall of a hallway. Based on the data set collected
from PIR sensors while a single person and a group of people
(two and three) walking in line as well as walking side by side,
they showed 100% correct detection of direction of movement
and 89% correct detection of number of people. The authors
also built a cluster system composed of two PIR sensors facing
each other in a hallway for detecting the direction of movement
and distance intervals (close to one sensor, in the middle, close
to the other sensor) when a person is walking