I've blogged about how we are to reliant on GPS, for example see: Are we to reliant on GPS/GNSS? Royal Academy of Engineering says we are. Now the Department of Homeland Security is saying the same thing in the report:National Protection and Programs Directorate Department of Homeland Security
National Risk Estimate: Risks to U.S. Critical Infrastructure from Global Positioning System Disruptions
The Office of Infrastructure Protection
Bottom Line: U.S. critical infrastructure sectors are increasingly at risk from a growing dependency on GPS for positioning, navigation, and timing (PNT) services. Such dependencies are not always apparent
"Human skills for using manual techniques could erode due to lack of training and practice as GPS becomes more ubiquitous", means that just because we have calculators and computers does not mean we should not teach and learn to do math with paper and pencil, and how to use a sextant. Also few understand how the banking and stock market have become dependent on timing synchronized transactions, at the nano-second or better levels of accuracy and precision.
For more information visit, http://www.dhs.gov/criticalinfrastructure, today. The day-after-tomorrow may be to late. Space Weather is reporting that sunspot AR1748 may release more X-Class flares this week, this time directed toward Earth. See Geomagnetic Storms: An Evaluation of Risks and Risk Assessments, 2011.
See also, The National Infrastructure Advisory Council Final Report and Recommendations on the insider threat to critical infrastructures, 2008 and Critical Infrastructure Partnership Advisory Council 2012 annual update.