“…Directional statistics is a subfield of statistics that deals with quantities defined on manifolds such as the unit circle or the unit hypersphere. Originally mostly developed with geoscientific applications in mind (Mardia 1981;Bingham 1974;Gaile and Burt 1980), directional statistics has gained widespread interest in various areas during the past decades, for example in biology (Batschelet 1981;Mardia, Taylor, and Subramaniam 2007), robotics (Glover and Kaelbling 2014;Feiten, Lang, and Hirche 2013;Markovic, Chaumette, and Petrovic 2014), machine learning (Banerjee, Dhillon, Ghosh, and Sra 2005;Gopal and Yang 2014;Diethe, Twomey, and Flach 2015), aerospace (Horwood and Poore 2014;Darling and DeMars 2015;, and signal processing (Traa and Smaragdis 2013;Azmani, Reboul, Choquel, and Benjelloun 2009;Drude, Chinaev, Vu, and Haeb-Umbach 2014). A good introduction to the topic can, for example, be found in the book by Mardia and Jupp (1999).…”