We may look to the night sky for answers, but sometimes, what matters most is what we can see looking down. For Yashena Naidoo, a spatial data scientist and researcher at the Gauteng City-Region Observatory (GCRO), the glowing lights of Johannesburg led to economic insight. Her work turns satellite-based night-time imagery into a proxy for understanding where economic activity thrives and declines across Johannesburg.

Naidoo’s research began as an experiment for GCRO’s “Map of the Month” series, when she came across freely available satellite data to visualise light intensity across Gauteng. “The lights are all artificial, a nd t hey represent w here w e are,” she says, or, put another way, the lights are a proxy for human and economic activity.