Study of Deflection of the Vertical Determination Methods and the Influence on the Traditional Terrestrial Three-Dimensional Geodetic Measurements

In present Global Navigation Satellite Systems (GNSS) are extensively used for national geodetic networks development and surveying. However, there are some applications where GNSS observations have to be integrated with traditional three-dimensional terrestrial geodetic measurements (e.g., underground engineering surveying, hydro electrical construction monitoring etc.). In order to integrate the GNSS observations and traditional measurements using total stations, it is necessary to know the Deflection of the Vertical (DoV), defined as the angle between the gravity vector that coincide with plumb line and the ellipsoidal normal in a given point. This paper is focused on studies of DoV components influence on the traditional terrestrial three-dimensional geodetic measurement: distance, horizontal and vertical angles. DoV components were calculated in the test network using geodetic (ellipsoidal) height differences determined by GNSS measurements and normal height differences from levelling network. The preliminary results show the necessity to use 1-II order levelling measurements and at least 1 hour GNSS observation in order to determine DoV components with a level of precision comparable to the angular accuracy achievable by 1 arcsec precision total station.