Function wmo_geopotential_from_geometric_m 

pub fn wmo_geopotential_from_geometric_m(
    height_msl_m: f64,
    latitude_rad: f64,
) -> Result<f64, AtmosError>

WMO geopotential height Z (gpm) of geometric height height_msl_m at geodetic latitude latitude_rad, by WMO-No. 8 (2023), Vol. I, eqs. 12.15 and 12.16 (after Mahoney):

Z = (γ_s(φ)/γ₄₅) · R(φ) z / (R(φ) + z)
γ_s(φ) = 9.780325 (1 + 0.00193185 sin²φ) / (1 − 0.00669435 sin²φ)^½
R(φ) = 6378.137 km / (1.006803 − 0.006706 sin²φ)

WMO puts 30 km at 29.7785 km of geopotential at the equator and 29.932 km at 80° N.

Errors

AtmosError::Domain if a value is not finite, the latitude is beyond ±90°, or the height is at or below −R(φ).