code: def rectifying(ell: Ellipsoid = None) -> float:
      """computes the radius of the sphere with equal meridional distances as the ellipsoid
  
      Parameters
      ----------
      ell : Ellipsoid, optional
            reference ellipsoid
  
      Returns
      -------
      radius: float
          radius of sphere
      """
      if ell is None:
          ell = Ellipsoid.from_name("wgs84")
      return (
          (
              ell.semimajor_axis ** (3 / 2)
              + ell.semiminor_axis ** (3 / 2)
          )
          / 2
      ) ** (2 / 3)
  
file_path: pymap3d/src/pymap3d/rsphere.py
imports: from __future__ import annotations
  from .None import rcurve
  from .ellipsoid import Ellipsoid
  from .mathfun import cos, degrees, log, radians, sin, sqrt
  from .vincenty import vdist
label_desc: Use image node_id 3 for calling a global function with example usage: rectifying(ell) and returns: unknown