Sharpness Old (1827) and New (1874) Docks and the canal as far as the Severn Bridge. CRT codes have been used for the location data with the main 'GS' set starting at the tide gate at the entrance to the tidal pool in the New Docks. The arm to the Old Docks has the prefix 'OA' and is measured from the junction with the arm the to the New Docks.