The master's thesis brings attention to the procedures and results of the control of the elevation accuracy in selected geodetic plans. Elevations in the areas of geodetic plans were specified with the method of trigonometric levelling and with reference to benchmarks. The elevation accuracy in geodetic plans has been tested in order to evaluate the influence of the vertical datum changes in Slovenia. Our analysis includes 17 examples of geodetic plans from all over Slovenia. The thesis presents the results of the comparison between the elevations calculated to different vertical data with elevations in geodetic plans. Furthermore, a comparison of heights referring to vertical datums of Trieste, Koper and Amsterdam has been made.