TOAR-II HEGIFTOM Focus Working Group
Harmonization and Evaluation of Ground-based Instruments for Free Tropospheric Ozone Measurements (HEGIFTOM)

A Focus Working Group in the Tropospheric Ozone Assessment Report, Phase II (TOAR-II, 2020-2024).
Working Group Leads: Roeland Van Malderen & Herman G.J. Smit
A rather broad and popular presentation highlighting the background, objectives and achievements of HEGIFTOM can be found here.
Schematic of different techniques measuring vertical ozone profiles.