The basic quantity of strain are determined vectors of velocity or displacement of de- formed body. Determination of displacements in geodetic practice is possible only with repeated survey of a geodetic net. Coordinates of points in geodetic net are estimated in each survey on a basis of observations. Thesis presents datum parameters of specific type of observation in projection plane and methods of datum assurance in geodetic nets. Velocity or displacement vectors are estimated from repeated surveys, where different survey techniques were used. Estimation is taking place in one step for all survey epochs in 4D space. Results are estimated coordinates of points in some reference epoch with corresponding velocity vectors. Velocity vectors are biased because of bad datum defi- nitions in separate surveys. These vectors are datum dependent, while strain tensor is invariant to transformation, but dependent on scale of a net. Vectors are analyzed on datum alterations presence and datum independent velocity vectors are obtained, which represent relative displacements of points in geodetic net. Main purpose of this thesis is to present a method of velocity vectors estimation from repeated surveys, that represent geometric displacements and are not biased because of datum alterations in separated surveys
