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Posted on 06/04/2008 11:13:45 AM PDT by Dawnsblood
Satellite-based navigation has become a ubiquitous tool for business, military and personal use. The downside is that any disruption in the Global Positioning System could wreak havoc down on Earth.
This year, the Department of Homeland Security decided that a 30-year-old navigation system used by mariners will be upgraded to back up GPS. The decision preserves the Long-Range Aids to Navigation (LORAN) network, which has been teetering on the verge of forced retirement since the 1980s, according to the Coast Guard’s Navigation Center.
The backbone of LORAN is a network of transmission stations, many located in remote regions, staffed with Coast Guard personnel, and equipped with antennas as tall as 900 ft.
The 2009 DHS budget allocates $34.5 million for the Coast Guard to start upgrading the LORAN system with modern electronics and solid-state transmitters. Users of the enhanced system, called eLORAN, will acquire and track signals from ground stations in much the same way they triangulate signals from multiple satellite feeds.
LORAN also adds a data channel that can handle more detailed information. The system won’t just wait for GPS to fail: eLORAN stations will continually transmit time-keeping data needed for navigation and warnings about coming disruptions.
(Excerpt) Read more at popularmechanics.com ...
Interesting. I thought LORAN had already been deactivated years ago.
}:-)4
I work for a company under contract with the FAA developing aviation instrument approaches and departures. More and more approaches and departures use GPS (referred to with the term RNAV, Area Navigation) as their sole source of guidance, no ground based navigational aids. There are no procedures or standards established for using LORAN as a substitute for GPS in aviation approaches and departures.
What I’m wondering is, what happens during a storm? Being as that GPS relies on satellite signals, wouldn’t a thunderstorm disrupt the signal? I have satellite TV and Wi Fi internet service. Whenever a thunderstorm comes up, I lose both signals for several minutes. Wouldn’t the same be true for GPS?
I wouldn’t think LORAN has the precision to fly an RNAV arrival or GPS approach, does it? I guess if GPS failed, everybody would have to start flying the old-school way with VORs and NDBs.
}:-)4
LORAN-C works at 100 kHz, so it couldn’t provide the level of resolution you would need to land an aircraft. It could get you to the airfield, and possibly it could tell one end of the runway from the other. Not good enough.
TACANS and ADFs rock!
The problem is that the FAA has been de-commissioning most of the NDB’s in the lower 48, too expensive to maintain and the minimums are very high compared to RNAV. This is especially common at smaller, general aviation airports. With RNAV the pilot gets a better approach with much lower minimims. There are no standards developed for using Loran for approaches and departures. Additionally, every Loran station I know of is located on the coast, none are located within the US. The day may come when so many procedures are based upon GPS that there are no VOR’s and NDB’s to fall back upon.
Me, too. Satellite TV operates at X-Band, about 11 GHz, GPS is at L-Band about 1.4 GHz. The effect of rain on radio waves is roughly proportional to the fourth power of frequency. (Cf. "Rayleigh Scattering"). (11/1.4)^4 ~ 3800. A given amount of rain will reduce an X-Band signal about 3800 times more than an L-Band signal.
DirecTV has about 6.0 dB (4X) link margin, meaning that they transmit about four times as much power as you need on a clear day. Whenever the link attenuation increases by a factor of four, - invariably due to rain - you lose the ability to receive. In practice, you experience about 24 hours of outage per year due to rain (99.7% availability).
L-Band only experiences the negligible attenuation due to rain.
I have no idea what frequency WiFi operates at.
G Standard at 2.4 Gig, N Standard at 5. Gig.
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Non-jammable. Worked for me for 20 years.
yeah, but that assumes a few things. One, that they will not find the “potemkin satellites”. Two, that they will some how get all the other layers of communication we are developing which integrate with satellites. Three, don’t think for a minute that we don’t have some very clever top secret back ups.
8.6 and 163 times the sensitivity to rain of L-Band, respctively.
The issue is frequency of update. GPS updates its position five times a second. LORAN (I believe) updates its position once a second. If LORAN can match GPS' update rate it should be fine for non-precision approaches.
For approaches and deportures it would make more sense to use publish alternates for VOR, DME and ADF instrumentation. A lot of IFR-capable aircraft are not equipped with LORAN but most (if not all) carry VOR, DME and ADF equipment.
/johnny
>This year, the Department of Homeland Security decided that a 30-year-old navigation system used by mariners will be upgraded to back up GPS.
30?
LORAN has been around for more than 80 years.
Yes, it is still online and usable.
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