The Global Positioning System (GPS) is currently facing a potentially serious threat resulting from proposed ground stations that would send ground-based radio signals that may interfere with GPS signals.
You can learn more about this issue at SaveOurGPS.org.
Coalition to Save Our GPS
The Coalition to Save Our GPS is working to resolve a serious threat to the Global Positioning System. A company has been granted a conditional waiver by the FCC to build 40,000 ground stations in the U.S. that could cause widespread interference to GPS signals—endangering a national utility which millions of Americans rely on every day.
Source: Save Our GPS