Abstract: The invention relates to measuring apparatus for measuring the dimensions of a large object with the aid of a narrow optical measuring beam directed onto a number of measuring points. A hit indicator unit is placed in connection with each measuring point. The apparatus includes rail which can be placed adjacent the object to measured and which carries a measuring carriage which is movable along the rail and which directs the direct the narrow optical measuring beam at an angle relative to the measuring path in an object reference plane. The carriage is moved rectilinearly along the rail. Each hit indicator unit coacts with an indicating arrangement which automatically indicates a hit by measuring beam. The carriage is provided with an automatically indicating rail-position sensor and the indications given by the sensor are read-off with each automatic hit indication through the medium of the indicating arrangement.

Abstract: A scale pattern is placed in close proximity of a measuring point whose position is to be determined in at least one dimension with the aid of a narrow measuring beam which moves in one place and sweeps over the scale pattern as it moves. The scale pattern is such that an indicating arrangement which indicates impingement of the measuring beam on the scale pattern gives rise to different signal patterns from a beam detector (25) for different heights at which the measuring beam sweeps over the scale pattern. The scale pattern has reflective and non-reflective pattern parts. Each scale pattern includes part-patterns (63, 64; 84, 85; 90, 91; 102, 105) which are operative in providing time or position scale-calibration for the signal pattern obtained from the beam detector (25) as the measuring beam sweeps over the scale pattern.