120 L. Tașçi.
Dam deformation measurements with GPS
4.5. Interpretation of the results A 2-dimensional deformation analysis was made
Water levels were 170.34 m in first period, 167,53 m – in because of a lower accuracy of the Z component with
the second period, 164,20 m – in the third period, and respect to the X and Y components. Therefore, for furt-
177,23 m – in the final period. In between 3 epochs obser- her work, in order to determine the movement in the
ved, because of a larger electric production and no rainfall, vertical dimension, the use of a precise levelling or anot-
water level has decreased. The reduction of water level in her method that has the potential to provide a vertical
between the 3 epochs is 6,14 m. This reduction caused the accuracy equal to or greater than the horizontal accuracy
movement of points on the dam’s crest. These horizontal of GPS is recommended.
movements on the crest could occur in the middle of the In conclusion, in regard to a magnitude of the dis-
dam crest in arch dams was proved by the GPS measure- placements, there is neither threat to the structural and
ments and deformation analysis methods (Fig. 4). functional security of the dam nor to the lives and pro-
perty of people living in the vicinity.
References
Chen, Y. Q. 1983. Analysis of deformation surveys. A genera-
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requirements for dam deformation measurements. object points in the deformation networks (Deformasyon
Ağlarýndaki Referans ve Obje Noktalarýnýn Hareketli
GPS is an effective method for static deformation
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concepts and applications. Ann Arbor Press. Inc. Chelsea,
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tream (Fig. 4). Singh, R.; Setan, H. 1999. Comparison of different datum de-
In this study, the most significant movements have finitions in detection of deformation of a geodetic monito-
ring networks, in Presented at Research Seminar on Cons-
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truction, Materials and Environmental Technology. 3–4
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vation have also been provided by the results of deforma-
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Deformation parameters obtained from the results Wellesley-Cambridge Press, USA.
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relation. Besides, both methods have the capability of de- Altýnkaya dam GPS measurements by minimum norm qu-
termination of the single point displacements free from adratic unbiased estimation (MINQUE). International Sym-
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comparing the LAS method with the IWST method, the Wellenhof, B. H.; Lichtenegger, H.; Collins, J. 1992. GPS theory
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ments of the LAS method is more effective with respect Öztürk, E.; Şerbetçi, M. 1992. Adjustment Vol III (Dengeleme
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cement vectors, obtained by the LAS method, the points
with a displacement greater than or equal to 4 mm were Levent TAŞÇI, Assoc. Prof., Dr. Fýrat University, Elazýğ, Tur-
accepted as unstable. This coincides with the horizon- key, Ph +424-2370000-5404.
tal accuracy of the observations calculated by MINQUE Research interest: Global Positioning System, deformati-
(Gökalp 1991; TaŞçi, Gökalp 2002). on measurements and analysis.
