Note the articles about eLoran and GPS...

[Michael O'Dell]

GPS World is admittedly the flagship pub of the GNSS industry,
but everything discussed here has been discussed and bore-out
in peer-reviewed journals such as those of the Institute
for Navigation (ION).  ION is the scholarly science and engineering
society which encompasses GNSS, among other things.

http://www.gpsworld.com/

the Obama administration has zeroed-out funding for Loran,
claiming an eLoran upgrade would cost zillions over many years.
in point of fact, the upgrade is almost complete at a comparative
pittance as such programs usually go.  therefore shutting down
the Loran stations after all that work is just throws away all \the 
money already spent on the upgrades for a system vitally important
as a backup for GPS.

Which leads to item number two.

the GPS constellation is very much at risk. It would be nice
if there were a functional backup system. This is also required
by the FAA if real ADS-B-aided area navigation is to be pursued
as the way to increase capacity of the airspace system.

the insight and commentary article on intentional GPS interference
is also sobering reading if one cares about reliable, precision
Postion, Navigation, and Timing (PNT) signals. all the more reason
eLoran is critically important to prevent a massive 
single-point-of-failure liability.

	-mo