static void SavePly(CartGridData map, string fileName, IProgress <int> progress)
        {
            try
            {
                var outputFilename = BuildFileName(fileName, "", ".ply");
                Debug.WriteLine("writing PLY file " + fileName);
                var plyF = new PlyFile();
                plyF.BuildFromGrid2(map);
                plyF.SaveAscii(outputFilename);

                Debug.WriteLine("finished writing ply file");
            }
            catch (Exception)
            {
                throw;
            }
        }