Inside the Government's Backup Plan for GPS Failure

Popular Mechanics

With the threat of everything from antisatellite weapons to solar flares, the Department of Homeland Security is upgrading an old navigation system to eLORAN to track signals across the country, Lost-style.

By Joe Pappalardo
Published on: June 3, 2008

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.

Why GPS Needs a Backup Plan

Intentional Jamming
Threat: GPS signals use low-powered, high-frequency signals that are easy to block.
eLORAN Fix: Uses high-powered transmitters that send stronger signals requiring more power to disrupt.

Environmental Interference
Threat: Signals from GPS sats need to be in the line of sight of receivers and are blocked by metal, mountains and reinforced concrete.
eLORAN Fix: Terrestrial signals bend around the Earth’s curvature and can penetrate urban canyons and dense foliage.

Cosmic Radiation
Threat: Unusually large solar flares can produce radio bursts over the same frequency bands as GPS satellite transmissions.
eLORAN Fix: Cosmic radio waves cannot penetrate the ionosphere, so LORAN signals are immune to interference.

Antisatellite Weapons
Threat: Future ground-based missiles could target and knock out GPS satellites.
eLORAN Fix:Ground stations can be more easily guarded from attacks, including those by missiles.

Of course, the fact that we have fewer LORAN receivers is a problem.  Time to start installing LORAN backups

And the Coasties keep getting to garrison places like Boise City, OK!

so where do I buy me a loran unit?

Bring back OMEGA!

I flew a Travelair with a KLN-89B in it...street cred, baby.

You could build and fly LORAN approaches...not that I ever did.

So when are we going to see dual receiver GPS/eLORAN hand held units? There are lots of areas here where GPS doesn't work so well.

Can combined signal processing yield more accuracy than just GPS?

I don't think there is real synergistic advantages, and LORAN is suceptible to rain fade and some other wierd atmospherics to which GPS is by design, immune.

eLORAN, as I understand, is about as accurate a non-WAAS/LAAS GPS...8 M or so.

It would provide RNP0.1 accuracy, but I think rain fade alone would limit the 95% time requirement.

I wonder if we have any military equipment that's using the Russian GLONASS system as backup,  of course without bothering to say much about it?


CJ

Quoted: I wonder if we have any military equipment that's using the Russian GLONASS system as backup,  of course without bothering to say much about it? CJ

Uh, GLONASS sucks.  The birds are unreliable, the constellation is imcomplete and coverage is spotty, even in Russia.

Quoted: So when are we going to see dual receiver GPS/eLORAN hand held units? There are lots of areas here where GPS doesn't work so well. Can combined signal processing yield more accuracy than just GPS?

Most places where GPS won't work, LORAN won't either...

They are both RF-based, and if you're in an RF hole, you're still in the hole weather the transmitter is in space or on land...

Or, we could all learn how to read a map and a compass...

LORAN was the GPS in the fishing industry back in the 80's.

Aren't the Euros launching the Magellan position system?

Quoted: Or, we could all learn how to read a map and a compass...

It doesn't work so well out of sight from land for more than a handfull of days, but I get what you mean.

Do they still print the Loran grids on charts?

Quoted: Aren't the Euros launching the Magellan position system?

Galileo.

Quoted: Or, we could all learn how to read a map and a compass...

Works better for walking than it does for other modes of transpo...

Clock/map/ground -> OH SHIT mode, not a viable nav method under normal circumstances....

That's good news... it's an excellent complement to GPS and using the two in combination is better than either.