For over a century, doctors have used electrocardiograms (EKGs) to render the invisible electrical activity of the human heart visible, using the pulse to diagnose disease before it becomes fatal. Now, scientists have invented a way to do the exact same thing for the places where most of humanity lives: cities.

In a recent study published in the Proceedings of the National Academy of Sciences, researchers introduced the concept of the “Urban Pulse.” By using dense, high-frequency satellite imagery, the team successfully tracked the dynamic, real-time metabolic activity of urban environments, effectively measuring the heartbeat of a city.

Zhe Zhu, director of the Global Environmental Remote Sensing (GERS) Laboratory and associate professor of natural resources and the environment in the College of Agriculture, Health and Natural Resources (CAHNR), was the first author. He worked in close collaboration with senior author Karen C. Seto, the Frederick C. Hixon Professor of Geography and Urbanization Science at the Yale School of the Environment, alongside Michail Fragkias of Boise State University and a multi-institutional team of researchers.