Advanced sensors for things like GPS signals are under development.

The problem comes from distortions in the GPS signal caused by the atmosphere around you.

And then launch it into orbit to interrupt GPS signals coming down?

GPS signals are already very weak when they arrive at the Earth's surface.

Also the Next generation air traffic control systems is being built around clear GPS signals.

Now mess up the GPS signal and planes go bang into each other.

This works using GPS signals telling the device exactly how far away from certain frequencies in use it is.

They take temporary refuge in a tunnel where the GPS signal is lost.

This is a significant advantage in certain applications since a GPS signal can still be lost indoors.

The rescue helicopter searched the region where they were supposed to be according to their last GPS signal.