Complex sentence: The North American Datum of 1927 (NAD27) is a datum based on the Clarke Ellipsoid of 1866; it was created by way of manual surveying of the entire continent.
Split into simpler sentences: The North American Datum of 1927 (NAD27) is a datum based on the Clarke Ellipsoid of 1866. This Ellipsoid was created by way of manual surveying of the entire continent.