Milestone-Proposal:LORAN: Difference between revisions

Revision as of 21:30, 10 December 2010

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Pierce Loran.pdf
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 Today's loran operates on one of several frequencies between1700 and 2000 kHz. It enjoys propagation characteristics determined primarily by soil conductivity and ionospheric conditions. Both ground wave and sky waves can be used to provide coverage over an  extensive area with few stations.  Usually. stations of a pairs are located 200 to 400 miles or more. At one time, several station pairs were separated by 1000 to 1400 miles apart.  Transmitters now in use radiate about 100kw and give a ground-wave range oversea water of about 700 nautical miles in the daytime. The day time range over land is seldom more than 250 miles even for high-flying aircraft and is scarcely 100miles at the surface of the earth. At night the ground-wave range oversea water is reduced to about 500 miles by the increase in atmospheric noise, but sky waves, which are almost completely absorbed by day,become effective and increase the reliable night range to about 1400miles. Generally, a number of stations are located so as to form a chain, with all but the end station in the group being double pulsing. In most parts of the world, signals  can be received from at least two pairs of stations  making it possible for a mariner to determine a fix using loran alone.
 A BRIEF HISTORY
-The name loran is derived from long-range navigation, a name given by Lawrence M. Harding, a career officer of the United  States Coast Guard (USGC). Harding is one of the loran pioneers we should not forget.  Beginning in 1943, USCG played a key role in getting some twenty-five loran transmitter stations up and running in the Aleutian Islands and the Pacific.  Pierce gives credit to the USCG for loran stations in Iwo Jima and Okinawa,  erected "upon the heels of the invading forces". Other loran stations in the Pacific guided the air force in its bombing campaign.  Until quite recently,  USGC crews have been manning loran stations in this part of the world for over 60 years.  The United States loran system was replaced by GPS and shut-down on 8 February 2010. The nominator witnessed this great event, perhaps planting the seed for this milestone nomination.
+The name loran is derived from long-range navigation, a name given by Lawrence M. Harding, a career officer of the United  States Coast Guard (USGC). Harding is one of the loran pioneers we should not forget.  Beginning in 1943, USCG played a key role in getting some twenty-five loran transmitter stations up and running in the Aleutian Islands and the Pacific.  Pierce gives credit to the USCG for loran stations in Iwo Jima and Okinawa,  erected "upon the heels of the invading forces". Other loran stations in the Pacific guided the air force in its bombing campaign.  Until quite recently,  USGC crews have been manning loran stations in this part of the world for over 60 years.  The United States loran system was replaced by GPS and shut-down on 8 February 2010. The nominator witnessed this great event on Nantucket, planting the seed for this milestone proposal.
 Other individuals should be mentioned:
-- Melville Eastman of the Microwave Committee:  First  leader of a small group organized under the newly formed Radiation Laboratory of the Massachusetts Institute of Technology. This group was responsible for developing a new radio navigation system. CEO and founder of General Radio Corporation of Cambridge, Eastman had taken a leave of absence from his company during 1941 to 1943.
+ Melville Eastman of the Microwave Committee:  First  leader of a small group organized under the newly formed Radiation Laboratory of the Massachusetts Institute of Technology. This group was responsible for developing a new radio navigation system. CEO and founder of General Radio Corporation of Cambridge, Eastman had taken a leave of absence from his company to work on the project from 1941 to 1943.
+ Jack Pierce,  a senior research fellow at Harvard University, Cambridge, MA joined the team in 1941.  He would later receive the Medal For Engineering Excellence in 1990 for the design , teaching and advocacy of radio propagation, navigation and timing which led to the development of Loran,  Loran C and other systems. He also received the 1948 Presidential Certificate of Merit and the 1953 Morris Liebmann Prize of the Institute of Radio Engineers.
-Jack Pierce,  a senior research fellow at Harvard University, Cambridge, MA joined the team in 1941.  He would later receive the Medal For Engineering Excellence in 1990 for the design , teaching and advocacy of radio propagation, navigation and timing which led to the development of Loran,  Loran C and Omega. Pierce,  Eastman and a small group of radio experts soon began testing the United States' first hyperbolic radio aid to navigation, investigating  radio frequencies, wave patters, reflection, and so on.
+Pierce,  Eastman and a small group of radio experts soon began testing the United States' first hyperbolic radio aid to navigation, investigating  radio frequencies, wave patterns, propagation, reflection, and so on.
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 Jack Pierce's epic article published by the IEEE in 1946 is the prime source for the information here.
-Among his many awards are a 1948 Presidential Certificate of Merit and the 1953 Morris Liebmann Prize of the Institute of Radio Engineers.
-JA Pierce was . . .???/////
-LORAN CITATION
 JA Pierce
 “In less than 5 years, loran, the American embodiment of a new method of navigation, has grown from a concept into service used by tens of thousands of navigators over three tenths of the surface of the earth. Even under the stress of military urgency, the direct cost of this system has been less than two percent of the seventy-five million dollars so far spent for operational equipment. ” JA Pierce 1946.
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 BOSDWITCH pdf
 Principle
-A crude diagram of the LORAN principle - the difference between the time of reception of synchronized signals from radio stations A and B is constant along each hyperbolic curve; when demarcated on a map, such curves are known as "TD lines"
-The navigational method provided by LORAN is based on the principle of the time difference between the receipt of signals from a pair of radio transmitters.[6] 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.
-A LORAN network with only two stations cannot provide meaningful navigation information as the 2-dimensional position of the receiver cannot be fixed due to the phase ambiguities in the system and lack of an outside phase reference.
-A second application of the same principle must be used, based on the time difference of a different pair of stations. In practice, one of the stations in the second pair also may be—and frequently is—in the first pair. In simple terms, this means signals must be received from at least three 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.
-L
-TODAY LORAN-C was originally developed to provide radionavigation service for U.S. coastal waters & was later expanded to include complete coverage of the continental U.S. as well as most of Alaska. Twenty-four U.S. LORAN-C stations work in partnership with Canadian and Russian stations to provide coverage in Canadian waters and in the Bering Sea. They system provides better than 0.25 nautical mile absolute accuracy for suitably equipped users within the published areas. and provides navigation, location, and timing services for both civil and military air, land and marine users. It is approved as an en route supplemental air navigation system for both Instrument Flight Rule (IFR) and Visual Flight Rule (VFR) operations. The LORAN-C system serves the 48 continental states, their coastal areas, and parts of Alaska. Dedicated Coast Guard men and women have done an excellent job running and maintaining the LORAN-C signal for 52 years. It is a service and mission of which the entire Coast Guard can be proud.
 Quote from extracted from
 Website entitled LORAN A