Pilot Balloons

Aviators required accurate information on winds at all altitudes. By releasing neoprene rubber balloons - pilot balloons, or "pibals" - and tracking them as they climbed with telescopic instruments called theodolites, meteorologists could plot wind speed and direction with a good degree of accuracy. This 1944 Navy aerology training manual describes the procedure, which was conducted at least twice a day from airports and military installations all over the country, as well as from ships at sea, in the 1940s and 50s.