A type of evaporation gauge or evaporimeter; it is a pan used in the measurement of the evaporation of water into the atmosphere. The U. S. Weather Bureau evaporation pan (Class-A pan) is a cylindrical container fabricated of galvanized iron or other rust-resistant metal with a depth of 25. 4 cm (10 in. ) and a diameter of 121. 9 cm (48 in. ). The pan is accurately leveled at a site that is nearly flat, well sodded, and free from obstructions. The water level is maintained at between 5 and 7. 5 cm (2 and 3 in. ) below the top of the rim, and periodic measurements are made of the changes of the water level with the aid of a hook gauge set in the still well. When the water level drops to 17. 8 cm (7 in. ), the pan is refilled. Its average pan coefficient is about 0. 7. See also BPI pan, Colorado sunken pan, floating pan, screened pan.