Position–velocity diagrams of the APEX CS 5−4, H¹³CO⁺ 3−2, H¹³CO⁺ 4−3, C¹⁷O 2−1, and C¹⁸O 2−1 transitions perpendicular a), b), c) and parallel d) to the filament. Linear fits are shown as straight lines. For C¹⁷O 2−1 and C¹⁸O 2−1 in c) the two outer points from either side of the curve were excluded from the fits. Fits to the innermost positions of C¹⁷O 2−1 and C¹⁸O 2−1 are also displayed.