The problem of optimization of geodetic networks has been extensively examined in geodetic science for the last 40 years. Despite extensive researches and progression at this field of study, it is still considered that general and unique solution of optimization does not exist, which is confirmed by countless procedures that solve the optimization problem depending on one or a group of criteria. These procedures, based on selected criteria, contain certain limitations, that prevent an universal solution, in spite of that, some methods provide reliable and practically useful results. In selected terrestrial networks in Slovenia, which are established for the purposes of control measurements, will be shown the use of the second order optimization. Measurements in these networks have been carrying out for longer period, they started average of more than 10 years ago. Until today, none of these treated networks had been completely optimized, therefore, the purpose of this work is to verify, if the measurements carried out in individual network, are actually needed and what impact the individual measurements have on the accuracy, when determinating the coordinates of points. This will give us an optimal plan of measurements, that will satisfy the requirements of the criteria of accuracy and could be realized with the available measuring equipment as well as lower costs.