What datum ellipsoids do NAD27 and NAD83 use? The North American Datum 1927 (NAD27) datum uses the Clarke 1866 ellipsoid. The North American Datum 1983 (NAD83) uses the GRS 1980 / IUGG 1980 ellipsoid. Updated: October 5, 2016 Have more questions? Submit a request 0 Comments Please sign in to leave a comment.