The deformation analysis from the point of view of its subject and methodology is an extensive part of geodetic and other methods for watching objects´ stabilities and for the determination of their changes using suitable quantities from deformation measurements performed in more epochs. In the monitoring of the object deformations, their characteristic points – object points (OB) are measured and their stabilities or movements are registered relating to a convenient number of robust reference points (RB) in the surroundings. It often happens in the monitoring that some RBs are lost (damage, destruction, etc.), resulting in datum changes of the deformation net and making a reliable stability evaluation of the OBs impossible.In this contribution to the problems of right datum determination for the whole net, three methods are introduced to reduce various datums to one of them for the whole deformation net, when the original (1st) datum can not be used in all epochs.