A measurement system including a tracking measurement device, a tracked measurement device, and a positioning unit disposed at least partly on the tracked measurement device. The positioning unit includes a tracking groove formed in a surface of the positioning unit, the tracking groove having a non-repeating pattern, and a positioning target configured to interface with the tracking groove so as to be movable within and along at least a portion of the tracking groove, where the positioning target is configured to interface with the tracking measurement device to effect a position determination of the tracked measurement device in a global coordinate system of the tracking measurement device.