eLoran: Articles and Blogs

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Are you confused? I'm confused. First I hear they're going to shut down the old Loran system. Then I hear they've going to update it into a robust alternative and backup to GPS. But then I read they're going to shut it down after all.

This most recent announcement was made last month, when President Obama's proposed budget was released. Here's an excerpt from the White House's New Era of Responsibility document:

"The Budget also supports the termination of outdated systems such as the terrestrial-based, long-range radionavigation (LOrAN-C) operated by the U.S. Coast Guard resulting in an offset of $36 million in 2010 and $190 million over five years."

There's an old joke that happens to include my surname in the punchline: "Off again. On again. Gone again. Flanagan." It's a joke about trains, not Loran. Still... What the heck's going on with Loran?

In fact it's not just bureaucratic inconsistency. Oh, there's some degree of that, to be sure, with various stakeholders contributing to a sort of long-term, glacially-paced global conversation about Loran technology in the United States and elsewhere.

But it isn't that alone. The other source of confusion for those of us who merely sit on the sidelines of the discussion is that they may be talking about two different systems.

TWO DIFFERENT THINGS

Loran-C is the system that came into widespread civilian use after the Vietnam War. Tremendously innovative when introduced, it remained the state of the art in reliable electronic navigation until GPS gained enough momentum to overshadow it in the 1990s.

[This nautical chart includes the familiar hyperbolic Loran-C time-difference (TD) lattices. NOAA's National Ocean Service (NOS) intends to eliminate Loran-C lattices from future editions of NOS nautical charts starting this year.]

Enhanced Loran (eLoran) improves upon the familiar Loran-C system with updated equipment and protocols. It promises to offer better performance and additional services, while remaining compatible with most Loran-C receivers. (For a more detailed description, see Mad Mariner' story on eLoran)

So when you hear "Loran is going to be decommissioned," they're talking about Loran-C. And when you hear "Loran is alive and well, and it's about to become a whole lot better," they're talking about eLoran.

Maybe you already knew this. I certainly didn't.

But once I figured it out, I started asking more questions. Mostly, I wanted to understand what distinguishes eLoran from Loran-C, and whether there really is a "future" for Loran.

GPS DEPENDENCY

There is a growing understanding that GPS is vulnerable to intentional, unintentional and natural interference and a legitimate concern that we have become overly dependent on GPS. This concern extends beyond aviation and marine navigation, too. In telecommunication and power distribution systems, for instance, GPS receivers generate timing signals used to synchronize massive networks affecting the daily lives and businesses of tens of millions of Americans. It is no exaggeration to suggest that GPS pervades our national infrastructure.

While GPS technology is satellite-based and very high frequency, Loran uses ground-based transmitters and is low frequency. Loran signals are very high-powered, so they penetrate cities, buildings and dense foliage where GPS signals can be blocked. Because of its high power, Loran is virtually impossible to jam.

The traditional Loran-C system, however, does not constitute an adequate backup system for GPS. But, proponents claim, it could, if only it were...well..."enhanced." Enhanced Loran, or eLoran, is a Loran system that incorporates updated receiver, antenna, and transmission system technology to enable Loran to back up and complement global navigation satellite systems (GNSS) for navigation and timing. This new technology provides substantially enhanced performance beyond what was possible with Loran-C, including much improved location accuracy - good enough for harbor entrances and non-precision runway approaches. Also, eLoran can function as an independent, highly accurate source of timing signals for network and power grid synchronization.

OFF AGAIN, ON AGAIN

For the past several years, eLoran transmission infrastructure has been gradually installed in the U.S., and a variation of eLoran is now operational in northwest Europe.

But wait a minute! If eLoran is so valuable, just what is it the Obama budget proposes decommissioning? Doesn't eLoran mostly involve installing new equipment at existing Loran-C facilities? So we should maintain those facilities through the transition, right?

Apparently not.

A bit of clarity seemed to emerge earlier this month when U.S. Coast Guard commandant Admiral Thad Allen responded to a question about Loran-C decommissioning on his blog:

"The President will propose in the Fiscal Year 2010 Budget that LORAN C be terminated, the stations shutdown. We are developing plans as to how we will execute the task when it is approved by Congress. Accordingly, it is difficult at this point to provide timelines or to address the issue of a backup for GPS, which is a separate and distinct issue. This decision will certainly force the discussion."

He emphasized this again, later in the same document: "The Loran-C system was not designed to be and is not a systemic backup for the positioning, navigation, and timing provided by GPS. A decision on eLoran will be made independently."

So in a way, I'm right back where I started: confused.

Does eLoran require a whole new network of ground stations, all scratch-built from the ground up? If so, then these surely are separate and distinct issues.

But what if that's not the case? Sherman Lo, a research associate at Stanford University's GPS Research Laboratory, says "enhanced Loran is designed to use the existing Loran system, modernized equipment, and a minimal amount of changes to achieve the required performance."

I'm no expert, so maybe it's naïve for me to suggest that perhaps we could save money, in the long run, by maintaining the Loran-C network and upgrading existing Loran-C stations to eLoran standards bit by bit.

I'm willing to be proved wrong on this. I don't come to this discussion with a bias or any special wisdom, so I hope experts with genuine knowledge will come forward and set me straight.

I'm just really curious about why Loran seems to be so "Off again, on again, gone again."