Selection of a filament. The three maps from left to right in the upper panel display line-of-sight velocity v_los (in  km s^-1), field inclination γ (in degrees), and temperature T (in K). The diamonds are selected points lying along the filament’s axis, between which a spline interpolation is performed. The area selected for the study of this filament is covered by the transverse lines. The v_los, γ, and T of the selected filament in its de-stretched and scaled form at log   (τ) = 0 are shown in the lower panel.