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These instruments are also used to measure the angular distance between objects: Octant, invented in 1731. The first widely accepted instrument that could measure an angle without being strongly affected by movement. Sextant, derived from the octant in 1757, eventually made all previous instruments used for the same purpose obsolete.
A sextant. A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of celestial navigation.
In navigation the instrument is also called a cross-staff and was used to determine angles, for instance the angle between the horizon and Polaris or the sun to determine a vessel's latitude, or the angle between the top and bottom of an object to determine the distance to said object if its height is known, or the height of the object if its distance is known, or the horizontal angle between ...
In aviation, distance measuring equipment (DME) is a radio navigation technology that measures the slant range (distance) between an aircraft and a ground station by timing the propagation delay of radio signals in the frequency band between 960 and 1215 megahertz (MHz). Line-of-visibility between the aircraft and ground station is required.
For that reason, Admiral John Campbell, who conducted shipboard experiments with the lunar distance method, suggested a larger instrument and the sextant was developed. [ 10 ] From that time onward, the sextant was the instrument that experienced significant development and improvements and was the instrument of choice for naval navigators.
Thomas Walker & Son were inventors and makers of nautical instruments in the 19th and 20th centuries. The firm made one of the most commonly used navigation instruments, the 'log' which allowed sailors to measure distance at sea, [1] [2] one of the main measurements used in nautical navigation. The firm was founded by Thomas Walker in ...
The time interval needs to be adjusted according to the distance between knots. Substituting 6,000 feet for 1 mile, the above formula yields 28.8 seconds for a distance of 8 fathoms. In fact, 28-second and 14-second glasses used to be common among navigation equipment. [9] Chip log in the 18th century
By modern measure, this is about 1 degree, 36 minutes, and 25 seconds, or just over 1.5 degrees. It is equal to the arcsine of the ratio of the width of the finger to the length of the arm. In Chinese navigation, the unit of jiao 角 is also used to represent a quarter 指 (an angle of 24 minutes 6 seconds).
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