Oh wow, cool to see this on HN!

I'm a postgraduate researcher working on GNSS interferometric reflectometry (GNSS-IR), a related but slightly different technique.

I'll shout out this awesome open source project, where you can use GNSS-IR and your own RINEX files to measure tides or soil moisture around your antenna: https://gnssrefl.readthedocs.io/en/latest/

(Your antenna needs to be near the sea or bare soil, respectively)