ChronosLoc is a camera-free, privacy-preserving system that shows how many people are in each room of a building and how this changes over time. Phones and laptops regularly send short Wi-Fi signals while searching for networks. ChronosLoc observes these signals through the building's existing Wi-Fi access points and a few low-cost sensing modules, and estimates where devices are on the floor plan; machine learning that uses the recent history of each signal corrects the errors caused by walls and reflections. Devices are anonymised the moment they are observed, and results are shown only as room- and zone-level figures. Sensing modules in selected rooms also detect people who carry no phone. A live web dashboard shows occupancy on the floor plan, heat maps and trends, helping facility, energy and emergency teams decide based on how spaces are actually used.
