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A 1931 U.S. Coast and Geodetic survey illustration of radio acoustic ranging using anchored station ships. Radio acoustic ranging, occasionally written as "radio-acoustic ranging" and sometimes abbreviated RAR, was a method for determining a ship's precise location at sea by detonating an explosive charge underwater near the ship, detecting the arrival of the underwater sound waves at remote ...
Aboard ship a dead reckoning plot is considered important in evaluating position information and planning the movement of the vessel. [8] Dead reckoning begins with a known position, or fix, which is then advanced, mathematically or directly on the chart, by means of recorded heading, speed, and time. Speed can be determined by many methods.
When a vessel (ship or boat) is within radar range of land or fixed objects (such as special radar aids to navigation and navigation marks) the navigator can take distances and angular bearings to charted objects and use these to establish arcs of position and lines of position on a chart. [32]
Navigation and location of the ship by geopositioning techniques based on the observation of the stars and other celestial bodies. The variables measured to find the location are: the observed angular height of the stars above the horizon , measured with the sextant (formerly with the astrolabe or other instrument), and the time , measured with ...
Radar ranges and bearings can be very useful for navigation. Radar navigation is the utilization of marine and aviation radar systems for vessel and aircraft navigation.When a craft is within radar range of land or special radar aids to navigation, the navigator can take distances and angular bearings to charted objects and use these to establish arcs of position and lines of position on a ...
A ship seen to be on a constant bearing with decreasing range will collide with the observer's ship unless avoiding action is taken. Constant bearing, decreasing range ( CBDR ) is a term in navigation which means that some object, usually another ship viewed from the deck or bridge of one's own ship, is getting closer but maintaining the same ...
A Dead Reckoning, DR, is calculated by using a previously determined position on a chart, and advancing that position based on known or estimated speed over a set amount of time. This can be calculated by using the formula Speed = Distance ÷ Time. [3] Once an advance position has been plotted, then set and drift can be factored in.
A diagram of a typical nautical sextant, a tool used in celestial navigation to measure the angle between two objects viewed by means of its optical sight. Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space or on the ...