The Use of Statistical Assumptions at Determining the Support Network Points Tudor SĂLĂGEAN 1 , Paul SESTRAŞ 1,2* , Mircea ORTELECAN 1 , Dumitru ONOSE 3 , Adrian SAVU 3 , Raluca Farcaş 4 , Andra PORUŢIU 1 1 University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca, Calea Mănăştur 3-5, 400372, Cluj-Napoca, Romania, Phone: +40264.596.384, Fax: +40264.593.792 2 University of Agronomic Sciences and Veterinary Medicine Bucharest, 59 Mărăşti Blvd, District 1, 011464, Bucharest, Romania, Phone: +4021.318.25.64, Fax: + 4021.318.25.67 3 Technical University of Civil Engineering Bucharest, Faculty of Geodesy, Department of Topography, Lacul Tei 122-124, District 2, 020396, Bucharest, Romania 4 Technical University Cluj-Napoca, Faculty of Constructions, Department of Land Measurements and Cadastre, Memorandumului 28, 400114, Cluj-Napoca *)Corresponding author, e-mail: psestras@yahoo.com BulletinUASVM Horticulture 72(2) / 2015 Print ISSN 1843-5254, Electronic ISSN 1843-5394 DOI:10.15835/buasvmcn-hort: 11580 Abstract In many cases, the coordinates values of the support network, which were determined at different epochs, varies in the limit of measurement and calculation errors. In this case the problem is which of these points from the support network are fixed and which are displaced. The purpose of this paper is to establish the fixed points in the case of repeated measurements in a support network. Based on repeated measurements which were made in the support networks related to hydropower objectives, were used the statistical assumptions in order to determine the displacements of the points from one epoch to another. The instrumental observations in the support network were made with high precision total stations. Based on statistical verifications performed in the support network related to Drăgan Valley dam, from the eleven pillars, three pillars were established as fixed point. The statistics calculated for the other pillars is higher than the statistics extracted from tables, so these pillars could not be considered as fixed points. After the calculations, because the values of the point displacements from one epoch to another were very small, the determination of the pillars stability can only be achieved through statistical tests. The verification of the support network stability is extremely important because if the azimuthal measurements made on the tracking landmarks are made from station points which are displaced, then the coordinates of the tracking landmarks will be inaccurate. Keywords: dam, displacement, landmark, support network. INTRODUCTION When designing tracking stations, related monitored objectives, it must be taken into account to ensure the accuracy required for determining the displacements of the sighting landmarks and also to ensure the stability of the stations during the entire period of observations (Ortelecan and Pop, 2005). The exact determination of the observation stations displacements is required, because a wrong determination of the displacements may distort the shape deformations of the construction. The accuracy of determining the sighting marks increases when the station are closer to the researched object. The observation stations are placed in the vicinity of the monitored construction, at distances that do not exceed 300- 400 m. A necessary condition for accurate determi - nation of absolute displacements of constructions