2. Geometric measurement methods

2.1 Atmospheric measurements

Atmospheric phenomena of particular interest to topographers are :

• refraction (variations in the refractive index that cause a change in the speed and direction of electromagnetic waves, which affects angle, distance and GNSS measurements);

• scattering, radiation interaction, either with :

  • air molecules and atoms (Rayleigh scattering),

  • aerosols and small dust particles suspended in the air (Mie scattering), which plays a direct role in the radiometry of aerial or space images required for photogrammetry.

Rayleigh scattering is intimately linked to the ultraviolet...