code: def segment_tripoints(self, ratio=0.33333):
          
  
          segments = self.identify_segments()
          points = self.points
  
          mids1 = ratio * points[segments[:,0]] + (1.0-ratio) * points[segments[:,1]]
          mids1 /= np.linalg.norm(mids1, axis=1).reshape(-1,1)
  
          mids2 = (1.0-ratio) *  points[segments[:,0]] + ratio * points[segments[:,1]]
          mids2 /= np.linalg.norm(mids2, axis=1).reshape(-1,1)
  
          mids = np.vstack((mids1,mids2))
  
          midlls = xyz2lonlat(mids[:,0], mids[:,1], mids[:,2])
  
          return midlls
docs: Identify the trisection points of every line segment in the triangulation