Definitions of the limits of the Severn Estuary vary. A narrower definition adopted by some maps is that the river becomes the Severn Estuary after the Second Severn Crossing near Severn Beach, South Gloucestershire, and stretches to a line from Lavernock Point (south of Cardiff) to Sand Point near Weston-super-Mare. The definition used on Admiralty Chart SC1179 and the Bristol Channel and Severn Cruising Guide is that the estuary extends upstream to Aust, the site of the old Severn Bridge. The estuary is about wide at Aust, and about wide between Cardiff and Weston-super-Mare.