From left to right and top to bottom: (1) column density (Fig. B.1, panel 3) after an asinh transform (colour scale is linear, not logarithmic); (2) structures resulting from the aspect-ratio filter of Frangi et al. (1998) applied to the Hessian eigenvalues of the transformed column density, with a single detection scale of 0.14 pc; (3) the samestructures after applying a gradient-based ridge-detection filter, with the same detection scale; (4) the result of the multi-scale (0.06–0.3 pc) filtering; (5) regions identified as filamentary, by applying a threshold onto the multi-scale filtered map; and (6) skeleton obtained by morphological thinning of these regions. The filaments that end up being eliminated at some point in the cleaning process are indicated in red.