Collection: Pilot balloons

A pilot balloon is used by meteorologists to determine the height of the base of clouds above the ground during daylight hours. The balloon is inflated to a level that determines its ascent rate. The measured time between the balloon's launch and its entry into the cloud allows the height of the cloud base to be determined. By tracking the trajectory, formerly with a theodolite, but now using radar or GPS, the direction and speed of high-altitude winds can be determined.