1. A method for optically scanning and measuring an environment by means of a hand-held scanner for producing 3D-scans, the method comprising: providing a hand-held scanner having at least one projector and at least one camera; projecting at least one pattern onto an object in the environment with the at least one projector; circumnavigating the object with the hand-held scanner and recording with the at least one camera images of the object which has the pattern projected thereon with a plurality of frames; determining three-dimensional coordinates of points on the surface of the object from each frame in the plurality of frames; and determining a ring closure in the plurality of frames following the circumnavigation of the object, the determination comprising the steps of: forming a frustum for each frame; comparing a last frustum of the last frame with a plurality of frusta to form an intersection; selecting a frustum having the largest intersection.