ground truth
n.— «Weather spotters provide what’s called “ground truth” to the National Weather Service and emergency weather management. “We’re needed because cloud-piercing Doppler radar is very good at helping the National Weather Service see what’s going on in the upper atmosphere, but it’s unable to detect what’s actually happening on the ground because of the curvature of the Earth.”» —“Volunteers track storms” by Debra Carr-Elsing Capital Times (Madison, Wisconsin) Oct. 26, 2006. (source: Double-Tongued Dictionary)
Further reading
Need a book to lift you out of this world? Try Orbital (Bookshop|Amazon). In it, Booker-winning novelist Samantha Harvey imagines the moment-to-moment experience of living on a space station, a mixture of the mundane and the majestic, 250 miles...
