A system includes a laser tracker, a camera bar, an accessory, and an electrical system, the camera bar including a mounting structure, two cameras, and three non-collinear reflector points, the accessory including a plurality of light markers, the electrical system including a processor that causes the tracker to measure 3D coordinates of the three reflector points, to measure the light markers with the cameras, and to determine a position and orientation of the assembly in a tracker coordinate system.