Characterising arbitrary dark solitons in trapped one-dimensional Bose-Einstein condensates H. A. J. Middleton-Spencer, N. G. Parker, L. Galantucci and C. F. Barenghi EPL, 133 1 (2021) 16001 Published online: 05 March 2021 DOI: 10.1209/0295-5075/133/16001