Abstract: A method of reconstructing the surface of an object by the boundary element method (BEM), approximately describes a measured, closed object surface (K) by a number of initial triangles, the position of the vertices (E1, E2) of which is known and also the normals (n.sub.1, n.sub.2) to the measured object surface (K) at these vertices (E1, E2), the initial triangles are replaced by sub-triangles, having no more than two vertices corresponding to vertices of an initial triangle (E1, E), in order to enhance the approximative description. An as accurate as possible description of the surface is obtained at little cost in respect of storage time and calculation time in that a curved connecting line (P) is determined through two vertices of the initial triangle (E1, E2) in such a manner that the connecting line (P) extends perpendicularly to the normals (n.sub.1, n.sub.2) at the vertices of the initial triangle (E1, E2), and in that a new vertex of a sub-triangle (E31) is chosen on the curved connecting line (P).