code: def get_uv_tan(c):
      
      l = c.spherical.lon
      b = c.spherical.lat
  
      p = np.array([-np.sin(l), np.cos(l), np.zeros_like(l.value)]).T
      q = np.array([-np.cos(l)*np.sin(b), -np.sin(l)*np.sin(b), np.cos(b)]).T
  
      return np.stack((p, q), axis=-1)
docs: Get tangent plane basis vectors on the unit sphere at the given
      spherical coordinates.