The thesis presents the analysis of the impact of the recent vertical move-ments of the Earth‘s crust on the measurements of levelling as well as levelling networks submitting the results of theoretical research and practical observa-tions.

The aim of the work is to investigate the impact on the results of measure-ments in terms of levelling and levelling networks, to work out the methodology for their evaluation to be applied in compiling and maintaining of these net-works.

The objectivity of the experiments deals with the levelling networks of Lithuania and data received.

The following tasks were solved: 1) there was perfected the methodological approach for the evaluation of the forecasting models in terms of geoindexes of the territory with intention to improve the forecasting.; 2) there was theoretically grounded as well as worked out the methodology for the evaluation of the im-pact of the recent vertical movements of the Earth’s crust on the measurements of levelling and on levelling networks; 3) there was derived the methodology of reduction of differences of measured altitudes, taking into account the selected moment of time; 4) there were made investigations on the possibilities of up-grading the models of forecasting by applying diverse groups of geoindexes; the recommendations were prepared how to use the models of forecasting; 5) while applying the proposed methods and recommendations there were carried out the experiments and evaluation of the impact of the recent vertical movements of the Earth’s crust on the levelling networks of Lithuania; 6) after summarizing the theoretical and experimental investigations made, there were derived the rec-ommendations for the evaluation of the impact of the vertical movements of the Earth’s crust on levelling networks.

By applying the proposed methodology targeted to reduce the results of measurements of levelling and taking into consideration the selected moment of time, there was achieved the decrease of the impact of systematic errors on the errors of levelling network, which depend on the impact of the vertical move-ments of the Earth’s crust during the period of levelling procedure.

Raktažodžiai: vertical movements of the Earth’s crust, horizontal gradients on the vertical movements of the Earth’s crust, errors considering the impact of the vertical movements of the Earth’s crust