Optimization of Measurements in the Geodetic Network for Monitoring the Horizontal Deformations of the Rogojeşti Dam

The monitoring of the horizontal deformations of the dams in Romania was done by means of classical geodetic methods of angular measurements and, sometimes, of distance measurements. With the advent of GNSS technology, testing the capability of spatial geodetic networks to meet the precision requirements in monitoring the horizontal deformations of the engineering structures has begun. The case study was carried out for the monitoring network of the Rogojeşti dam, which is made of local materials and located on the Siret River, 12 km from its entrance in the north of Romania. Optimization of measurements in the monitoring network has been analysed from the perspective of global precision indicators (standard reference deviation) and errors in the horizontal positioning of new points, highlighted by the graphical representation of standard error ellipses. The optimization problems were taken into consideration by both the classic geodetic micro-triangulation network and the modern GNSS network, used either individually or through the horizontal distance components, in a combined micro-triangulation-trilateration geodetic network. The conclusions highlight that by combining both classical measurements (angular measurements) and GNSS measurements (by horizontal distance determinations), positioning errors can be diminished and an improvement in the geometric configuration of the error ellipses in the newly determined points compared to the simple network of geodetic micro-triangulation becomes noticeable.