Search results
Results from the WOW.Com Content Network
A protractor is a measuring instrument, typically made of transparent plastic, for measuring angles. Some protractors are simple half-discs or full circles. More advanced protractors, such as the bevel protractor, have one or two swinging arms, which can be used to help measure the angle. Most protractors measure angles in degrees (°).
Sighting the height of a landmark can give a measure of distance off and, held horizontally, a sextant can measure angles between objects for a position on a chart. [1] A sextant can also be used to measure the lunar distance between the moon and another celestial object (such as a star or planet) in order to determine Greenwich Mean Time and ...
In trigonometry, the gradian – also known as the gon (from Ancient Greek γωνία (gōnía) 'angle'), grad, or grade [1] – is a unit of measurement of an angle, defined as one-hundredth of the right angle; in other words, 100 gradians is equal to 90 degrees.
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.
By reversing the telescope and at the same time rotating the instrument through 180 degrees about the vertical axis, the instrument can be used in 'plate-left' or 'plate-right' modes ('plate' refers to the vertical protractor circle). By measuring the same horizontal and vertical angles in these two modes and then averaging the results ...
The protractor head can be used for: Measuring and checking angles between surfaces, edges, and markings. Marking angles from an edge; Directly transferring angles, like a bevel gauge (sliding T gauge), to minimise measurement errors and inaccuracies. Measuring and marking angles relative to the horizontal by using the spirit level. [2]
Since an mrad is an angular measurement, the subtension covered by a given angle (angular distance or angular diameter) increases with viewing distance to the target. For instance the same angle of 0.1 mrad will subtend 10 mm at 100 meters, 20 mm at 200 meters, etc., or similarly 0.39 inches at 100 m, 0.78 inches at 200 m, etc.
Many angle units are defined as a division of the turn. For example, the degree is defined such that one turn is 360 degrees. Using metric prefixes , the turn can be divided in 100 centiturns or 1000 milliturns, with each milliturn corresponding to an angle of 0.36°, which can also be written as 21′ 36″ .