DIFF Subgroup
G01C 21/38 Full Title
Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 (measuring distance traversed on the ground by a vehicle G01C22/00; control of position, course, altitude or attitude of vehicles G05D1/00; traffic control systems for road vehicles involving transmission of navigation instructions to the vehicle G08G1/0968)
Of 3 combined children, 0 exist in both systems.
3 codes are CPC-only extensions.