USGS → Fourier Mountain

Select terrain from USGS 3DEP, reconstruct it with 2D Cosine modes, and export a Desmos 3D equation.

Tip: keep the box roughly square and centered on one mountain. The grid is sampled from the live USGS 3DEP bare-earth elevation service.
Search for a location, then draw a rectangle around the terrain you want.
3D reconstruction No terrain loaded
RMSE — Energy —
Exported equation is Desmos-scaled: larger horizontal dimension maps to −5 to 5, and minimum elevation is shifted to 0.