openlifu.geo.spherical_coordinate_basis

openlifu.geo.spherical_coordinate_basis(th: float, phi: float) → ndarray

Return normalized spherical coordinate basis at a location with spherical polar and azimuthal coordinates (th, phi). The coordinate basis is returned as an array basis of shape (3,3), where the rows are the basis vectors, in the order r, theta, phi. So basis[0], basis[1], basis[2] are the vectors $hat{r}$, $hat{theta}$, $hat{phi}$. Angles are assumed to be provided in radians.