The earth is bathed in radiation from GPS transmitters and these clever satellites are using doppler radar techniques to see how those signals are being reflect

The earth is bathed in radiation from GPS transmitters and these clever satellites are using doppler radar techniques to see how those signals are being reflected from ocean waves. From the doppler shift you can infer wind fields. Consumer GPS receivers only compute position from these signals, but there is a lot of interesting science you can do from the raw signals with a hacked GPS receiver.