f in the direction of the x axis are measured by means of for example three ultrasonic or optical distance sensors 11 12 and 13 placed at known points in the space then the individual spatial coordinates of the three points f 1 f 2 and f 3 can be obtained by parallel translation of spatial coordinate values of the distance sensors 11 12 and 13 respectively in the direction of the x axis the plane including the front face f can thus be defined by the spatial coordinates thus obtained however the positions of the parallelepiped w in its rotational direction around an axis perpendicular to the plane and in a plane including the axis are still unknown subsequently spatial coordinates of two points g 1 and g 2 on a side face g of the parallelepiped w can be obtained in a similar manner by means of two distance sensors 21 and 22 placed at individually known points in short the spatial coordinates of the points g 1 and g 2 can be obtained by parallel translation of space coordinates of the distance sensors 21 and 22 respectively in the direction of the y axis in accordance with results of measurements by the distance sensors 21 and 22 since here the front face f and the side face g extend perpendicularly to each other if the space coordinates of the two points g 1 and g 2 are known then the plane including the side face g can be defined from them.