The Analysis of Monitoring Control Point Displacement of Sermo Dam Based on the 2015-2016 GNSS Data

Sermo dam has operated for 20 years. This dam has a great benefit, especially as a water storage for water supply, irrigation and flood prevention. For the purposes of Sermo dam deformation monitoring, the control network was built around the Se dam in 2010. Then, this network was developed in 2015 by adding 5 new control points. For the time being, the network consists of 8 existing control points (micro) and 5 new control points (macro). The aim of the study is to monitor the control network displacement in the period of 2015 to 2016 based on GNSS observation data.GNSS measurement were conducted at 9 to10 of May 2015 and 12 to 15 of May 2016. The data observation was processed using GAMIT/GBLOK scientific software referenced to IGS station to determine the coordinates and its standard deviation. Further, horizontal and vertical displacement was analyzed by comparing with 2.5 times the standard deviation. The results showed that within a year, the coordinate difference varied from 0.12 to 1.68 cm on the N component, 0.21 to 0.65 cm on the E component, while the U component (the vertical displacement) have greater one, varied from 2.71 to 16.34 cm. Six control points (MAK2, MAK3, BMB2, BM95, BMS2 and BMS5) have significant different in the horizontal displacement and six control points have significant different m vertical displacement (MAK5, BMM, BMB2, BMS1, BMS2 and BMS 3). In general, the horizontal displacement tends toward southeast. However, for obtaining more accurate and realistic results, further evaluation is required in the processing strategy such as the use of local control point as reference.