Estimated characteristic size for the observed ¹³CO emission in the line of sight as a function of the distance (r) from the center of the filament crest. The characteristic size is estimated combining the Herschel column density with the ¹³CO(3–2)/¹³CO(2–1) density estimate using the Herschel dust temperature (red) and a temperature of 10 K (blue). The horizontal lines indicate the characteristic sizes in the plane of the sky (POS) of the strands and the filament crest.