3. General measurement principles

There are a huge number of measurement techniques that can be used to study atmospheric pollution, but they can be grouped into two main categories, depending on whether they operate directly in the atmosphere (remote sensing techniques) or require sampling.

The former are of considerable theoretical interest, but are still complex to implement. They will be presented briefly in 3.1 . The latter are now the most widely used, and will be presented in detail in 3.2