“…Its main drawback is the selection of the number of clusters, which, as previously discussed, can be optimized by using an EM algorithm. An example of the maritime data clustering based on K ‐means can be found in Vespe, Pallotta, Visentini, Bryan, and Braca (); recently density‐based spatial clustering of applications with noise (DBSCAN) methods have become very popular for their convenient properties as compared to K ‐means: they are density‐based (which is a convenient property for the maritime data), they do not require to specify the number of clusters, they have the ability to derive arbitrarily shaped clusters and they incorporate by‐product the classification of the noise points; examples of such applications in the maritime domain can be found in Arguedas, Pallotta, and Vespe (), Pallotta and Jousselme (), Pallotta, Vespe, and Bryan () and Pallotta, Vespe, and Bryan (). Liu, De Souza, Hilliard, and Matwin () discusses an “ad‐hoc” similarity metric for trajectory partitioning and segment clustering, which can be seen as a DBSCAN version for trajectory clustering.…”