Back before GPS there was LORAN. Building on the success of the British GEE radio navigation system, the US military developed LORAN during World War II as a secret program to provide the Allies with a reliable and accurate means of navigation at sea in any weather. LORAN was originally called Loomis Radio Navigation (LRN), named after its inventor Alfred Lee Loomis. After the war ended the Coast Guard continued to expand LORAN for use by both the military and commercial shipping fleets. It has evolved through the years but has always been a reliable means of off-shore navigation, and eventually it was expanded to include support for aircraft.
LORAN works in a way very similar to GPS. Rather than satellites orbiting the Earth, LORAN consists of a series of ground stations, called a chain. There are numerous LORAN chains throughout the world. The precise position of each transmitter is well known, and each transmitter knows the exact time. A radio will lock in to a chain and listen to the broadcasts from each transmitter in the chain. From these broadcasts it will be able to calculate the difference in the signal delay between transmitters and thus it can determine its position. LORAN signals work well at sea and in the air, but not so well across uneven ground with building and other obstructions. Although it was easy to extend its use to aircraft, it was not practical for use on the ground.
When we purchased our Mooney 10 years ago it came with a LORAN receiver: a Northstar M1. We have used the M1 on almost every flight to track our progress and estimate arrival times over the fixes along our route. Although it was never approved as a sole navigational source in the clouds (IFR use) we still found it very useful when flying IFR as a supplemental tool.
As GPS became widespread and inexpensive, the popularity of LORAN began to wane. On May 7 2009, President Barack Obama proposed cutting LORAN funding. On the same day the U.S. General Accounting Office (GAO), the investigative arm of Congress, released a report stating there was a very real potential for the GPS system to degrade or fail. The GPS program has recently suffered delays in its schedule to launch replacement satellites, potentially threatening the system's reliability. On the heels of that report there was an effort to save LORAN in some form to act as a backup for GPS. But the administration decided against such efforts and supported efforts to "achieve an orderly termination through a phased decommissioning beginning in January 2010, and the requirement that certifications be provided to document that the LORAN-C termination will not impair maritime safety or the development of possible GPS backup capabilities or needs." In November the Coast Guard announced that it saw no impairment to maritime safety. In January Homeland Security concluded that LORAN was not essential, even as a backup for GPS. So an orderly shutdown of the US LORAN chains was scheduled to begin at 2000 UTC February 8, 2010. US participation in international chains will continue as required by treaty.
The budget for LORAN is $35 million per year. This comprises 0.001% of the federal budget.
The shutdown of the US LORAN chains means our Northstar M1 is now useless. So we will have to replace it with something a bit more modern. Goodbye LORAN. You were a valued and trusted navigational tool.