In the instructions to electronic total stations and in the modern references on electronic means of measurements there is no data of the root-mean-square error to determine excess using electronic total station. An average square error for the electronic total station of «Topcon» and «Nikon» is given. This article offers a traditional method of approach to organizing a study of measuring the excess of the trigonometric leveling using TS. The measured value is compared with the one which can be considered correct and then of the mean square error (RMSE) defined, gives the most accurate value of the standard deviation. In our case, the excess of the true dimension of the geometric leveling was taken from the II class course in the territory PMCs. Of course, all 11 sections were selected.