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? 

full_context: Document 1: Field marshal (India): Field marshal (or field marshal, abbreviated as FM) ( , ) is a five–star general officer rank and the highest attainable rank in the Indian Army. Field marshal is ranked immediately above general, but not exercised in the regular army structure. It is a largely ceremonial or wartime rank, having been awarded only twice. A field marshal's insignia consists of the national emblem over a crossed baton and sabre in a lotus blossom wreath.
Document 2: United States Navy officer rank insignia: In the United States Navy, officers have various ranks. Equivalency between services is by pay grade. United States Navy commissioned officer ranks have two distinct sets of rank insignia: on dress uniform a series of stripes similar to Commonwealth naval ranks are worn, while on service khaki, working uniforms (Navy Working Uniform [NWU], and coveralls), and special uniform situations (combat utilities, flight suits, and USMC uniforms when worn by Navy officers assigned or attached to USMC units), the rank insignia are similar (there are subtle differences in the size, shape, and design of naval services insignia) to the equivalent rank in the US Army or US Air Force.
Document 3: Fleet admiral (United States): Fleet admiral (abbreviated FADM), officially known as "Fleet Admiral of the United States Navy", is a five-star flag officer rank in the United States Navy. Fleet admiral ranks immediately above admiral and is equivalent to General of the Army and General of the Air Force. Although it is a current and authorized rank, no U.S. Navy officer presently holds it, with the last living U.S. Navy fleet admiral being Chester W. Nimitz, who died in 1966.
Document 4: Admiral (Germany): Admiral, short Adm, (en: Admiral) is the most senior flag officer rank in the German Navy. It is equivalent to General (Germany) in the German Army or German Air Force. In the Central Medical Services there is no equivalent. In the German Navy "Admiral" is, as in many navies, a four-star rank with a NATO code of OF-9. There is currently one admiral in the German Navy, Admiral Manfred Nielson, serving as Deputy Supreme Allied Commander Transformationin Norfolk, Virginia.
Document 5: Cap badge: A cap badge, also known as head badge or hat badge, is a badge worn on uniform headgear and distinguishes the wearer's nationality and/or organisation. The wearing of cap badges is a convention commonly found among military and police forces, as well as uniformed civilian groups such as the Boy Scouts, civil defence organisations, ambulance services (e.g. the St. John Ambulance Brigade), customs services, fire services etc.
Document 6: Grand admiral: Grand admiral is a historic naval rank, the highest rank in the several European navies that used it. It is best known for its use in Germany as "Großadmiral". A comparable rank in other navies is that of fleet admiral.
Document 7: Brazilian jiu-jitsu ranking system: The Brazilian jiu-jitsu ranking system is a means of signifying a practitioner’s increasing levels of technical knowledge and practical skill within the art of Brazilian jiu-jitsu. Colored belts that are worn as part of the uniform are awarded to the practitioner. While the ranking system's structure shares its origins with the Judo ranking system and that of all colored martial arts belts, the Brazilian jiu-jitsu ranking system grew to incorporate unique aspects and themes. The system has minor differences from Judo in areas such as a division between youths and adults and the issuance of stripes and degrees. Some distinct differences have become synonymous with the art, such as a marked informality in promotional criteria, a focus on a competitive demonstration of skill, and a conservative approach to promotion.
Document 8: Military rank: Military ranks are a system of hierarchical relationships in armed forces, police, intelligence agencies or other institutions organized along military lines. Usually, uniforms denote the bearer's rank by particular insignia affixed to the uniforms. 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.
Document 9: Other ranks (Denmark): Other ranks (or ORs) in the Royal Danish Army, Royal Danish Navy and Royal Danish Air Force is a joined term for military personnel that are not officers of various forces, by the NATO system of ranks and insignia. These personnel are NCOs and privates, seamen or aircraftsmen.
Document 10: List of United States Navy enlisted rates: A United States Navy enlisted rate indicates where an enlisted Sailor stands within the chain of command, and also defines one's pay grade. An enlisted sailor's rate is similar conceptually to a naval officer's rank. Only Naval Officers carry the term "rank". The word "rate" refers to an enlisted sailor's pay grade, while the word "rating" refers to one's area of occupational specialization within the enlisted Navy. Associated with the enlisted pay grades is a numbering system from the most junior enlisted sailor ("E-1") to the most senior enlisted sailor ("E-9"). This enlisted numbering system is the same across all five branches of the U.S. Military. All E-1 through E-3 are known as Seamen. E-4 through E-6 are called Petty Officers. All E-7s are called Chief Petty Officer, E-8s Senior Chief Petty Officer, and E-9s Master Chief Petty Officer. Rates are displayed on a rating badge, which is a combination of rate and rating. E-2s and E-3s have color-coded group rate marks based on their career field. Personnel in pay grade E-1, since 1996, do not have an insignia to wear.
Document 11: Erich Raeder pre Grand Admiral: Erich Johann Albert Raeder (24 April 1876 – 6 November 1960) was a naval leader in Germany before and during World War II. Raeder attained the highest possible naval rank—that of "Großadmiral" (Grand Admiral) — in 1939, becoming the first person to hold that rank since Alfred von Tirpitz. Raeder led the "Kriegsmarine" (German War Navy) for the first half of the war; he resigned in 1943 and was replaced by Karl Dönitz. He was sentenced to life in prison at the Nuremberg Trials, but was released early due to failing health. Raeder is also well known for dismissing Reinhard Heydrich from the Reichsmarine in April 1931 for "conduct unbecoming to an officer and a gentleman".
Document 12: Admiral of the fleet: An admiral of the fleet or fleet admiral (sometimes also known as admiral of the navy or grand admiral) is a military naval officer of the highest rank. In many nations the rank is reserved for wartime or ceremonial appointments. It is usually a rank above admiral (which is now usually the highest rank in peace-time for officers in active service), and is often held by the most senior admiral of an entire naval service.
Document 13: Field marshal (United Kingdom): Field Marshal has been the highest rank in the British Army since 1736. A five-star rank with NATO code OF-10, it is equivalent to an Admiral of the Fleet in the Royal Navy or a Marshal of the Royal Air Force in the Royal Air Force (RAF). A Field Marshal's insignia consists of two crossed batons surrounded by yellow leaves below St Edward's Crown. Like Marshals of the RAF and Admirals of the Fleet, Field Marshals traditionally remain officers for life, though on half-pay when not in an appointment. The rank has been used sporadically throughout its history and was vacant during parts of the 18th and 19th centuries (when all former holders of the rank were deceased). After the Second World War, it became standard practice to appoint the Chief of the Imperial General Staff (later renamed Chief of the General Staff) to the rank on his last day in the post. Army officers occupying the post of Chief of the Defence Staff, the professional head of all the British Armed Forces, were usually promoted to the rank upon their appointment.
Document 14: Admiral: Admiral is one of the highest naval ranks in some navies, and in many navies is the highest rank. It is usually abbreviated to "Adm" or "ADM". The rank is generally thought to have originated in Sicily from a conflation of Arabic: أمير البحر‎ ‎ , "amīr al-baḥr", "commander of the sea", with Latin "admirabilis" ("admirable") or "admiratus" ("admired"), the first was admiral Lumu Farouk, although alternative etymologies derive the word directly from Latin, or from the Turkish military and naval rank miralay.
Document 15: Erich Raeder: Erich Raeder (24 April 1876 – 6 November 1960) was a naval leader in Germany who played a major role in the naval history of World War II. Raeder attained the highest possible naval rank—that of Grand Admiral — in 1939, becoming the first person to hold that rank since Alfred von Tirpitz. Raeder led the "Kriegsmarine" for the first half of the war; he resigned in 1943 and was replaced by Karl Dönitz. He was sentenced to life in prison at the Nuremberg Trials, but was released early due to failing health.
ground_truth: Military ranks