The BBC reports that the Colombian researchers used video of the fireball taken from camera phones, car-dashboard cameras and CCTV footage, including traffic cams that contained precise time stamps:
"Using the footage and the location of an impact into Lake Chebarkul, Jorge Zuluaga and Ignacio Ferrin, from the University of Antioquia in Medellin, were able to use simple trigonometry to calculate the height, speed and position of the rock as it fell to Earth.
"To reconstruct the meteor's original orbit around the sun, they used six different properties of its trajectory through Earth's atmosphere. Most of these are related to the point at which the meteor becomes bright enough to cast a noticeable shadow in the videos."
Early estimates of the size of the Chelyabinsk meteor put it at about 10,000 tons, but NASA later estimated the object at between 7,000 and 10,000 tons. The energy released by the event was estimated at about 500 kilotons, or 30 times the power of the atomic bomb dropped on Hiroshima in World War II.