Testing of geometric quality of a precast unit is aimed at yielding reliable information on the features achieved at yielding reliable information on the features achieved in production. Therefore the authors present a measuring system consisting of a robot, the sensors and the coordinating computer. The main goal of this kind of measuring is to realize an objective low cost measuring procedure. The possibilities and the boundaries of this system are discussed. The authors show that this system is a first contribution in securing geometric shape with the help of automation of length-measuring process.