The shortest ground wavelength the canonical field carries, meters.
docs/adr/0019-the-geology.md names the canonical floor as roughly 0.5 m of
amplitude at ~8 m of wavelength, and this is the wavelength half of it. Below it,
detail is synthesized at render time and may differ between backends by
design — the divergence is bounded, named and measured rather than denied.
A landing ship spans tens of meters, so ground that is right to within this
is ground.