A measurement system for determining six degrees of freedom (.alpha., .beta., d, .phi., .chi., .psi.) of a reflector (2) or of an object (3) on which the reflector is arranged, comprises an angle- and distance measurement apparatus (1), e.g. a laser tracker, operating with a laser beam as a measurement beam (4). The reflector (2) is designed for a parallel reflection of the measurement beam (4) and has an apical opening or surface (6), in a manner such that a part of the measurement beam (4) directed onto the reflector (2), passes through the apical opening or surface (6), and is incident on a light-sensitive surface (7) arranged behind the reflector apex. Five degrees of freedom (.alpha., .beta., d, .phi., .chi.) of the reflector (2) or the object (3) are computed from measurement data produced by the angle- and distance measurement apparatus (1) and by the light-sensitive surface (7).