A system and a method for providing an indication about positioning unreliability are described. The system comprises a scanner for scanning a surface geometry of an object and accumulating 3D points for each frame using shape-based positioning; a pose estimator for estimating an estimated pose for the scanner using the 3D points; an unreliable pose detector for determining if the estimated pose has an under constrained positioning and an indication generator for generating an indication that the unreliable pose estimation is detected. In one embodiment, a degree of freedom identifier identifies a problematic degree of freedom in the estimated pose. In one embodiment, a feature point detector detects a reobservable feature point and the pose estimator uses the feature point with the 3D points to estimate the estimated pose and the unreliable pose detector uses the feature point to identify the estimated pose as an unreliable pose estimation.
