Each record should contain 1 image row. Cell values should be separated by a comma or a space(s). Note, it will be necessary to strip (delete) the header information from the image file if it exists, but be sure to keep it for later reference regarding background cell value, # rows, # columns, cell size, and nodata value. The default file name extension for a raw ascii grid is .asc for file navigation purposes, but any extension can be used.