eLORAN: Inside the Government's Backup Plan for GPS Failure

Lets look at what we have here. Currently we have the Global
Navigation Satellite System (GNSS or GPS). Most of us are now familiar
with this technology. But are you aware of WAAS (wide area
augmentation system)? This is a system on the satellite that makes
corrections so that the data is more accurate on your GPS receiver.
Differential GPS (DGPS) is a system that is similar to LORAN (ran by
the Coast Guard) that provides data correction in parallel with your
GPS. What all of these systems (WAAS, DGPS) do is take a known
location, compare that to the GPS data then transmit the corrections.

We see survey equipment that provides localized DGPS for survey teams
(and centimeter accuracy).

Aviation is moving to LAAS (local area augmentation system) that would
provide very accurate data so that aircraft can land under poor
visibility.

The Navy has systems in development for ships and this technology is
moving towards the civilian market as a replacement for ILS (IFR Cat
I, II, III landings).

VORTAC is going away, along with ILS. They are scheduled to be
replaced by a GPS/LAAS (local area augmentation system) combination.
LORAN-C was scheduled to go away however this new eLORAN looks to
merge DGPS and a ground based version of GPS (eLORAN) that could
augment GPS. We use old LORAN-C frequencies now for DGPS (100 KHz
system coupled with 1500 MHz GPS).

From what I have been able to read, eLORAN will be somewhat different
than LORAN-C. Instead of a master and several slaves, the new system
will be like GPS in that several stations are used by measuring the
time difference from each. Instead of a master-slave in a chain,
eLORAN uses all stations that your receiver can hear (like GPS can use
all satellites in view). It appears that it will provide DGPS services
as well.

Europe is pushing eLORAN due to the control of the GNSS by the US
military.

It is a cheaper, land based system that is in the control of many
nations.

Harder for terrorists to jam or destroy. Frequencies are between
90-110 KHz with transmitters at 1000 Watts to 1 MW. GPS is about 1500
MHz and milliwatts.

Here are some links that might provide more information. The Coast
Guard site has pages on GPS, DGPS and eLORAN.

http://www.navcen.uscg.gov/eLoran/overview.htm

http://www.torkildsen.no/Navconf2007/Offermans.pdf

http://www.locusinc.com/pdf/Loran%20...0w%20logo6.pdf

http://www.locusinc.com/library/2005%20RTCM_Locus.pdf

http://www.askhelios.com/ERNP/docume...t%20300606.ppt

http://www.mycoordinates.org/satelli...uthnmyths1.php

http://www.popularmechanics.com/tech...y/4266972.html

Inside the Government's Backup Plan for GPS Failure

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.

LORAN Station, Attu, Alaska: This is the view from the 600-ft. LORAN
tower.

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.