Transmissometer

A transmissometer or transmissiometer is an instrument for measuring the extinction coefficient of the atmosphere and sea water, and for the determination of visual range.

It operates by sending a narrow, collimated beam of energy (usually a laser) through the propagation medium.

Transmissometers are also used by oceanographers and limnologists to measure the optical properties of natural water.

[2] In this context, a transmissometer measures the transmittance or attenuation of incident radiation from a light source with a wavelength of around 660 nm, generally through a shorter distance than in air, as water has a smaller maximum visibility distance.

[citation needed] Latest generation transmissometer technology makes use of a co-located forward scatter visibility sensor on the transmitter unit to allow for higher accuracies over an Extended Meteorological Optical Range or EMOR.