8:46 PM Tue 9 Feb 2010 GMT
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'Loran-C chain coverage'
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The Long Range Aids to Navigation (Loran-C) system was a valuable position and navigation system when it was established in 1957, but it is about to go into history, made redundant by the GPS system.
The US Government, as part of an Obama economy package, has determined that it is not even needed as a back-up.
Transmission of the Loran-C signal and phased decommissioning of the LoranC infrastructure was due to commence on or about February 8, 2010. All Loran stations are expected to cease transmitting the LoranC signal by October 1, 2010.
On October 28, 2009, the President signed into law the 2010 Department of Homeland Security Appropriations Act. The Act allows for the termination of the LoranC system subject to the Coast Guard certifying that termination of the LoranC signal will not adversely impact the safety of maritime navigation and the Department of Homeland Security certifying that the LoranC system infrastructure is not needed as a backup to the GPS system or to meet any other Federal navigation requirement.
The decommissioning plans include ending transmissions at 18 Loran stations located in the contiguous United States and 6 Loran stations in Alaska. The Department of Homeland Security anticipates that all Loran stations will cease transmitting the LoranC signal by October 1, 2010.
About the Loran_C:
The U.S. LoranC system is a low frequency hyperbolic radionavigation system. A LoranC receiver measures the slight difference in time it takes for pulsed signals to reach a ship or aircraft from the transmitting stations within a LoranC chain to develop a navigational position. LoranC is approved for use in the U.S. Coastal Confluence Zone and as a supplemental air navigation aid. LoranC is operated and maintained by the U.S. Coast Guard.
The LoranC system was a valuable position and navigation system when it was established in 1957. As a result of technological advancements over the last 20 years and the emergence of the U.S. Global Positioning System (GPS), LoranC is no longer required by the armed forces, the transportation sector, or the nation's security interests, and is used only by a small segment of the population.
The LoranC system was not established as, nor was it intended to be, a viable systemic backup for GPS. Backups to GPS for safety of life navigation applications, or other critical applications, can be other radionavigation systems, or operational procedures, or a combination of these systems and procedures. Backups to GPS for timing applications can be a highly accurate crystal oscillator or atomic clock and a communications link to a timing source that is traceable to Coordinated Universal Time.
With respect to transportation to include aviation, commercial maritime, rail, and highway, the Department of Transportation has determined that sufficient alternative navigation aids currently exist in the event of a loss of GPSbased services, and therefore Loran currently is not needed as a backup navigation aid for transportation safety of life users.
by US Federal Register
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