Tank & Silo Fill-Level Field Imaging

WiFi waves travel differently through liquid or powder than through air, so the surface of the contents acts like an invisible line the signals can find. As the level rises or falls, that line moves and the signals crossing the vessel change with it.

In the physics: Liquid (water eps_r~80, hydrocarbons ~2-4) vs air creates a strong dielectric discontinuity at the fill surface. As level changes, multipath rays that graze or transit the vessel shift in delay (slower propagation through high-eps_r media) and amplitude (reflection coefficient at the air/liquid interface moves spatially). This is a geometry observable, not a motion observable.