Question: Grand Admiral a naval rank in one of the highest in the several European navies that use this system, what system are they using? 
Sentence (from "Military rank"): Ranking systems have been known for most of military history to be advantageous for military operations, in particular with regards to logistics, command, and coordination; as time went on and military operations became larger and more complex, military ranks increased and ranking systems themselves became more complex.
Relevant evidence: No