Observational calibration of the projection factor of Cepheids - I. The type II Cepheid κ Pavonis J. Breitfelder, P. Kervella, A. Mérand, A. Gallenne, L. Szabados, R. I. Anderson, M. Willson and J.-B. Le Bouquin A&A, 576 (2015) A64 Published online: 30 March 2015 DOI: 10.1051/0004-6361/201425171