GPS observations for geoid determination in Lithuania

Abstract

The GPS presents new possibilities for the Geoid determination. Together with traditional gravimetrical methods the connection of the Geoid to the Height System which in used. Institute of Geodesy, VTU had performed GPS observations at 1400 points of polygonometry, which already were leveled (IV order). Accuracy of these points' heights not always is known. Construction of fundamentation is not reliable. The points were leveled 10-20 years ago. The methodic of polygonometric points suitability for the Geoid Determination was selected. 1060 points were picked out. For more strict geoid orientation 41 bench marks of 1st and 2nd order leveling were coordinated by the GPS. The significant factors of the selection were: - points should be distributed evenly in the territory of the country; - preferably fixed by ground bench marks; - leveling should be done as late as possible. Bench marks were coordinated from Zero and First Order GPS Network’s stations. The standard deviations of the ellipsoidal heights were less than 15 mm. Some bench marks were rejected and finally only 36 were selected.