A system for tracking a position of a working edge on an implement of a construction vehicle includes a GNSS with an antenna. The GNSS unit is configured to determine a position of the antenna and a tilt and a heading of the GNSS unit. A mount is configured to couple the GNSS unit to a rigid member of the construction vehicle. The mount is configured to couple the GNSS unit to the rigid member so that the antenna is arranged in a known spatial relationship with a pivot point between the rigid member and the implement. A mobile controller is configured for wireless communications with the GNSS unit and an angle sensor that is configured to determine rotation of the implement. The mobile controller is configured to receive the position of the antenna, the tilt, and the heading from the GNSS unit, to receive the rotation of the implement from the angle sensor, and to determine coordinates of the working edge of the implement in a real world coordinate frame.