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The
larger truth, the one we missed, was how deeply dependent our whole infrastructure
was becoming on a GPS technology that was inherently vulnerable to what
are known as "unintentional" and "intentional" problems.
It’s all spelled out in this year’s Volpe Report, but had we
been listening back in 1999, we might have heard a well-informed skeptic
like Bond say, "If we rely on GPS alone, there is the risk, indeed
the likelihood, of multiple aviation and marine catastrophes."
The problem is the extraordinary
weakness of the GPS signal. It’s a marvel that our little handhelds
work as well as they do with data coming in at one ten-quadrillionth of
a watt, equivalent to light from a 20-watt bulb 11,000 miles away. Interference
from unexpected natural and man-made sources is easy. There is already
regular "ionosopheric interference" near the poles; an extended
period of solar flares could cause GPS malfunction in well-traveled areas.
Satellite navigation is said to be difficult in Italy because certain
TV channels are leaking spurious emissions. Recently, automated wireless
toll-taking devices installed on bridges have been discovered knocking
out local GPS reception.
These sorts of problems
will probably be solved with the next generation of GPS, which will add
new frequencies and possibly more power to the present signal. However,
the issue of "intentional" interference looks much harder, if
not impossible, to solve. Bond says, "Anyone with $50 and a soldering
iron can make a jammer able to destroy the GPS signal for a hundred miles."
The Volpe researchers, who clearly had access to at least some portion
of our military’s "dark" GPS technology, detail what a
more sophisticated enemy could accomplish. This includes not just widespread
and prolonged jamming, but also "spoofing" in which GPS misinformation
blankets the real signals.
You can easily imagine
the terrible consequences of fake navigation data in foggy harbors and
airports. In the aviation world it’s acronymed HMI for "hazardously
misleading information" and understood to be much more dangerous
than no information at all. But did you realize that many of our telecommunications
and power-grid systems are also dependent on GPS for atomic-clock timing
capabilities?
The whole scary story
is laid out in the Volpe report (available at www.navcen.uscg.gov)
and was apparently taken quite seriously by our secretary of transportation
Norman Minetta. He released it to the public last September 10, and of
course the horrid events of the following day could not have done more
to emphasize the presence of malevolent and clever forces in our world.
The notion of "sole source" electronic navigation has been officially
retired for at least the near future. The military, which knows more about
GPS vulnerability than anyone, already equips all its GPS-guided vehicles
and weapons with alternate electronic backup; the civilian sector, led
by Minetta’s DOT, will soon follow.
Much to my surprise,
Loran appears to be a prime backup candidate. I remember the complexity
of compensating for "Additional Secondary Factors" in coastal
waters and switching "chains" on long voyages, and then having
the darn signals fade away just short of Bermuda. No wonder the only currently
manufactured marine Loran I could find is Furuno’s solid but pricey
LC-90 (and the salesman assured me that I really didn’t need it because
GPS "never goes out").
Well, it turns out that
Loran has been quietly improving. When the DOT decided in the late ‘90s
that shutting down the transmitters was perhaps imprudent, it also began
to slowly replace old vacuum-tube units with more capable Megapulse solid-state
devices complete with cesium clocks. In October 2001 Megapulse received
a $40-million contract to complete this process ASAP. Meanwhile, small
industrial manufacturers have developed "all in view" Loran
receivers that can work with multiple signal chains. Pretty soon we should
see more accurate and easier to use Loran sets that will work very well,
at least around North America and Europe.
In our age, the ultimate
beauty of Loran is how different it is from GPS. With its high power,
low frequency, and land-based signals, Loran is much harder to jam or
spoof. Thus Bond and his ilk predict the proliferation of integrated GPS/Loran
units that can feed our digital charts, radar overlays, etc. with a new
level of electronic integrity. I look forward to this development, but
I have to admit that my research tends to support the gizmo-leery, belt-and-suspenders
approach to navigation that Richard Thiel advocated in his column. In
short, the boss was right.
Ben Ellison has been
a delivery captain and navigation instructor for nearly 30 years and was
recently the editor of Reed’s Nautical Almanacs.
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