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LORAN - LOng RAnge Navigation

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Post time 2018-10-24 13:20:33 | Show all posts |Read mode
LORAN (LOng RAnge Navigation)  , menentukan kedudukan kapal laut dan kapal terbang/pesawat , sekali lagi , manusia tak perlu satelit GPS . kalau satelit GPS wujud , mengapa kapal laut dan pesawat  kat lautan dalam , hilang fungsi GPS ?

krn ia hanya guna tower , kat laut dalam tiada tower .


LORAN (LOng RAnge Navigation) is a terrestrial radio navigation system which enables ships and aircraft to determine their position and speed from low frequency radio signals transmitted by fixed land based radio beacons, using a receiver unit.The most recent version of LORAN in use is LORAN-C, which operates in the low frequency (LF) portion of the radio spectrum from 90 to 110 kHz. Many nations have used the system, including the United States, Japan, and several European countries. Russia uses a nearly identical system in the same frequency range, called CHAYKA.In recent decades, LORAN use has been in steep decline, with the satellite-based Global Positioning System (GPS) being the primary replacement. However, there have been attempts to enhance and re-popularize LORAN, mainly to serve as a backup and land-based alternative to GPS and other satellite navigation systems.The current LORAN system has been phased out in the United States and Canada. The United States Coast Guard (USCG) and Canadian Coast Guard (CCG) ceased transmitting LORAN-C (and joint CHAYKA) signals in 2010...HistoryLORAN was an American development, advancing the technology of the British GEE radio navigation system that was used early in World War II. While GEE had a range of about 400 miles (644 km), initial LORAN systems had a range of 1,200 miles (1,930 km). It originally was known as "LRN" for Loomis Radio Navigation, after Alfred Lee Loomis, who invented the longer range system and played a crucial role in military research and development during World War II, but later was renamed to the abbreviation for the more descriptive term. LORAN systems were built during World War II after development at the Massachusetts Institute of Technology (MIT) Radiation Laboratory and were used extensively by the US Navy and Royal Navy. The RAF also used LORAN on raids beyond the range of GEE.In November 2009, the USCG announced that LORAN-C is not needed by the U.S. for maritime navigation...PrincipleThe navigational method provided by LORAN is based on measuring the time difference between the receipt of signals from a pair of radio transmitters. A given constant time difference between the signals from the two stations can be represented by a hyperbolic line of position (LOP).If the positions of the two synchronized stations are known, then the position of the receiver can be determined as being somewhere on a particular hyperbolic curve where the time difference between the received signals is constant. In ideal conditions, this is proportionally equivalent to the difference of the distances from the receiver to each of the two stations.So a LORAN receiver which only receives two LORAN stations cannot fully fix its position—it only narrows it down to being somewhere on a curved line. Therefore the receiver must receive and calculate the time difference between a second pair of stations. This allows to be calculated a second hyperbolic line on which the receiver is located. Where these two lines cross is the location of the receiver.In practice, one of the stations in the second pair also may be—and frequently is—in the first pair. This means signals must be received from at least three LORAN transmitters to pinpoint the receiver's location. By determining the intersection of the two hyperbolic curves identified by this method, a geographic fix can be determined.In the case of LORAN, one station remains constant in each application of the principle, the primary, being paired up separately with two other secondary stations. Given two secondary stations, the time difference (TD) between the primary and first secondary identifies one curve, and the time difference between the primary and second secondary identifies another curve, the intersections of which will determine a geographic point in relation to the position of the three stations. These curves are referred to as TD lines...

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This is a shortened version of the 1947 "LORAN for Ocean Navigation" filmstrip produced by the Coast Guard as a sales pitch to commercial shipping lines to adopt LORAN (as a both a navigational aid and to assist in distress situations).
Updated with a new narration track in place of the distorted period track, the film provides a brief wartime history of LORAN, and its significance to the American war effort.

credit - Smithsonian National Air and Space Museum



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credit - Jeff Quitney  
"LORAN (LOng RAnge Navigation) Technical training film - how it works."US Air Force training film FTA-356









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