def triangulate(self):
        """
        Convert mesh points to vectors in Cartesian space.

        :returns:
            Tuple of four elements, each being 2d numpy array of 3d vectors
            (the same structure and shape as the mesh itself). Those arrays
            are:

            #. points vectors,
            #. vectors directed from each point (excluding the last column)
               to the next one in a same row →,
            #. vectors directed from each point (excluding the first row)
               to the previous one in a same column ↑,
            #. vectors pointing from a bottom left point of each mesh cell
               to top right one ↗.

            So the last three arrays of vectors allow to construct triangles
            covering the whole mesh.
        """
        points = geo_utils.spherical_to_cartesian(self.lons, self.lats,
                                                  self.depths)
        # triangulate the mesh by defining vectors of triangles edges:
        # →
        along_azimuth = points[:, 1:] - points[:, :-1]
        # ↑
        updip = points[:-1] - points[1:]
        # ↗
        diag = points[:-1, 1:] - points[1:, :-1]

        return points, along_azimuth, updip, diag