scope:

For reasons of air quality control, both scientists and official authorities are displaying increasing interest in measuring the turbidity of the atmosphere due to air pollutants. The turbidity characterises the atmospheric content of turbid extinguishing particles and thus the pollution. It provides, therefore, information on long-term changes in air quality.

This standard describes the fundamental principles of measuring the meteorological optical range by using transmission and scattered light methods and includes directions on measurement planning as well as on data acquisition, transmission and analysis. The method of processing the readings should be included in the planning to ensure that the results are comparable; it is determined essentially by the particular measuring task involved.

Air turbidity measurement using the methods listed in this Standard is suitable for air quality monitoring over prolonged periods, e.g., for trend investigations in clean air regions or conurbations. Measuring the turbidity or the visual range is also significant in road traffic, aviation and shipping investigations.

Methods that use the sun as a light source (solar photometry) are unsuitable for continuous measurements of air turbidity, and therefore are not covered in this standard. Methods for measuring the global radiation, the direct solar radiation and the radiation balance are contained in VDI 3786 Part 5. Measurements of visual range with Lidar are covered in DIN ISO 28902-1.

This standard does not cover visual range determination; for this, see also VDI 3786 Part 9.