The United States Geological Service maintains over 8500 "Gaging stations" in bodies of water all over the country. Gaging stations are devices that are used to measure environmental data such as groundwater levels, discharge, water chemistry, and water temperature. What's interesting is that they all upload their data in real time to GOES satellites - the same satellites that we can use with an RTL-SDR to receive weather images of the entire earth. The data is then downlinked in the L-band to the USGS scientists via a protocol known as DCP (Data Collection Platform).
In the latest SignalsEverywhere video, Corrosive investigates how these stations work, and how we can receive the downlink at 1.68 GHz with a simple Inmarsat L-band antenna. While a fully functional decoder is not yet available, Corrosive notes that one called goes-dcs is currently being worked on.