IMPACT OF VERTICAL GROUND MOVEMENTS ON ACCURACY OF REFERENCE GEODETIC LEVELLING NETWORK

Theoretical research enabled to work out the methodology targeted to estimate the impact of the recent vertical ground movements on accuracy of reference geodetic levelling network. The methodology proposed makes it possible to plan repeated geodetic measurements of levelling networks to achieve required accuracy. The methodology is presented allowing reduction of measured differences in altitudes taking into account trends in vertical ground movements in selected moment of time. By reducing the measurements the influence of systematic errors is decreased due to the impact of vertical movements of the Earth's crust on to the errors of levelling. Regressive models are derived by means of the general mathematical statistical analysis of repeated geodetic measurements and incorporation of geo-indexes. The models are applied in forecasting the velocities of vertical ground movements required for the evaluation of the impact of vertical movements of the Earth's crust on the measured differences of altitudes and for performing reduction of measurements notifying the selected moment of time. Explore to assess the impact of the vertical movement of the Earth's crust for the levelling networks of Lithuania. The conclusion derived implies that in 10 years about 70% of the first-class levelling networks would not satisfy the accuracy requirements for maintenance. Accuracy requirements for the second class network in 10 year would not be satisfied by about 55%. The sums of reduction corrections of altitude differences in separate observations, in terms of the Lithuanian first class levelling network when specifying the selecting moment of time, up to four times exceed the sums of normalized corrections.