Transmissometer

5-4-365

A device which assesses the visibility by measurement of the attenuation of radiation along a straight path through the atmosphere, resulting from the presence of particles which cause scattering and absorption of radiation out of the path. In a homogenous atmosphere, the attenuation can be directly related to the atmospheric transmission factor (2-1-270).

Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)