Knot (unit) in the context of "True airspeed"

A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. Historically, it was defined as the meridian arc length corresponding to one minute (⁠1/60⁠ of a degree) of latitude at the equator, so that Earth's polar circumference is very near to 21,600 nautical miles (that is 60 minutes × 360 degrees). Today the international nautical mile is defined as exactly 1,852 metres (about 6,076 ft; 1.151 mi). The derived unit of speed is the knot, one nautical mile per hour.

The nautical mile is not part of the International System of Units (SI), nor is it accepted for use with SI. However, it is still in common use globally in air, marine, and space contexts due to its correspondence with geographic coordinates.

A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its location and strength, a tropical cyclone is called a hurricane (/ˈhʌrɪkən, -keɪn/), typhoon (/taɪˈfuːn/), tropical storm, cyclonic storm, tropical depression, or simply cyclone. A hurricane is a strong tropical cyclone that occurs in the Atlantic Ocean or northeastern Pacific Ocean. A typhoon is the same thing which occurs in the northwestern Pacific Ocean. In the Indian Ocean and South Pacific, comparable storms are referred to as "tropical cyclones". In modern times, on average around 80 to 90 named tropical cyclones form each year around the world, over half of which develop hurricane-force winds of 65 kn (120 km/h; 75 mph) or more.

Tropical cyclones typically form over large bodies of relatively warm water. They derive their energy through the evaporation of water from the ocean surface, which ultimately condenses into clouds and rain when moist air rises and cools to saturation. This energy source differs from that of mid-latitude cyclonic storms, such as nor'easters and European windstorms, which are powered primarily by horizontal temperature contrasts. Tropical cyclones are typically between 100 and 2,000 km (62 and 1,243 mi) in diameter. The strong rotating winds of a tropical cyclone are a result of the conservation of angular momentum imparted by the Earth's rotation as air flows inwards toward the axis of rotation. As a result, cyclones rarely form within 5° of the equator. South Atlantic tropical cyclones are very rare due to consistently strong wind shear and a weak Intertropical Convergence Zone. In contrast, the African easterly jet and areas of atmospheric instability give rise to cyclones in the Atlantic Ocean and Caribbean Sea.

In kinematics, the speed (commonly referred to as v) of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a non-negative scalar quantity. The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero. Speed is the magnitude of velocity (a vector), which indicates additionally the direction of motion.

Speed has the dimensions of distance divided by time. The SI unit of speed is the metre per second (m/s), but the most common unit of speed in everyday usage is the kilometre per hour (km/h) or, in the US and the UK, miles per hour (mph). For air and marine travel, the knot is commonly used.

The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. More simply, the speed of sound is how fast vibrations travel. At 20 °C (68 °F), the speed of sound in air is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn), or 1 km in 2.92 s or one mile in 4.69 s. It depends strongly on temperature as well as the medium through which a sound wave is propagating.

At 0 °C (32 °F), the speed of sound in dry air (sea level 14.7 psi) is about 331 m/s (1,086 ft/s; 1,192 km/h; 740 mph; 643 kn).

SMS Panther was one of six Iltis-class gunboats built for the German Kaiserliche Marine (Imperial Navy) in the late 1890s and early 1900s. The ships were built to modernize the German gunboat force that was used to patrol the German colonial empire. They were ordered in three groups of two ships, each pair incorporating design improvements. Panther, along with Eber, was armed with a main battery of two 10.5 cm (4.1 in) guns, had a top speed of 13.5 knots (25.0 km/h; 15.5 mph), and could cruise for 3,400 nautical miles (6,300 km; 3,910 mi).

Panther spent most of her career abroad, where she was involved in a number of international disputes. She was initially sent to the East American Station after entering service in 1902, and she was soon sent to intervene in the Markomannia incident, where she sank the Haitian gunboat Crête-à-Pierrot. Panther was next involved in the Venezuelan crisis of 1902–1903, during which she participated in the bombardment of Fort San Carlos. Panther returned to Haiti in 1904 to pressure the Haitian government to pay a settlement after an attack on a German diplomat in the country. In 1905 and 1906, the ship toured South America, steaming as far south as Paraguay. She was transferred to German West Africa in mid-1907.

The Floréal class is a type of light "surveillance frigates" (French: frégate de surveillance) designed for the needs of the French Navy in low-threat environments ordered in 1989. The ships are named after months of the Republican Calendar. They use construction standards of commercial ships. The frigates were built between 1990 and 1993 by the Chantiers de l'Atlantique at Saint-Nazaire, France. The six French ships of the class, Floréal, Prairial, Nivôse, Ventôse, Vendémiaire and Germinal, remain in active service.

The ships' main armament was two Exocet MM38 surface-to-surface missiles and a 100 mm (4 in) CADAM turret, but in 2014, the Exocets were removed at the end of their life cycle. The vessels have a maximum speed of 20 knots (37 km/h; 23 mph) and can carry 24 marines. The vessels are used mainly to patrol the French overseas departments and regions in the Pacific, Indian Ocean and Caribbean regions, but have served in both military and humanitarian operations in the Persian Gulf and the Gulf of Guinea.