Lietuvos geodezinio vertikaliojo tinklo sudarymo principai

Abstract

Main principles of establishment and aspects of realisation of the Lithuanian geodetic vertical network as part of country’s geodetic network are analysed. Main purpose of the vertical network establishment is a creation of national geodetic vertical reference, according to the requirements of the international standards, suitable for the implementing new technologies of geodesy and cartography as well as for the needs of scientific problem solution. Vertical network should determine a unified geopotential height system in the territory of Lithuania and guarantee the reliable connection with height systems used in Europe. Therefore the network incorporates Lithuanian points observed during the international GPS campaigns such as EUVN (European United Vertical Network) and BSL (Baltic Sea Level). The vertical network will be composed of two different order networks. The first order network will consist of five polygons. Perimeter ca. 1900 kilometers. The main Lithuanian GPS points as part of EUVN and BSL networks: Vilnius, Siauliai and Molas are included. Monumentation of the points will be ground and wall benchmarks. Average distance between points will be 1.5 kilometer. Ground benchmark construction is suitable for the GPS observation. First order network will be densified by the second order network. Perimeter ca. 4500 kilometers. First and second order networks should be measured at the same time. Levelling network is the part of the vertical network. Levelling lines are adjusted with already existing levelling network. As many as possible benchmarks will be incorporated in new levelling lines. Measuring error models, accuracy of measurements, tests of measuring results as well as their control are analysed. According to the requirements of the network all geodetic, satellite geodesy and gravimetric observations should be coordinated and of a certain accuracy that root mean square error of the height difference of 1 kilometer first order levelling line should not exceed 0.5 millimeter, for the second order 0.7 millimeter. Such vertical network will create preconditions for the geoid improvement and will result in a higher accuracy of height determination by the GPS. Suggested structure of the network will enable the usage of the GPS for the height reference establishment for cartographical, surveying engineering and other needs.