Dwi Lestari
Teknik Geodesi, Fakultas Teknik, Universitas Gadjah Mada

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Comparison of Horizontal Displacement from Horizontal Control Network Adjustment Result Using Observation Model and Time-Variant Methods (Case Study : Horizontal Control Network of Borobudur Temple, Epoch 2002, 2003 and 2012) Een Lujainatul Isnaini; Dwi Lestari
Jurnal Geospasial Indonesia Vol 1, No 1 (2018): June
Publisher : Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jgise.38472

Abstract

Borobudur Temple is the biggest Buddhist Temple in the world protected by UNESCO. Therefore the periodical maintenance of Borobudur temple become important, deformation study through displacement analysis can be applied for it, by conducting Geodetic observation periodically. The design for Borobudur horizontal monitoring network is a relative one, the control point and monitoring points are in the deformation area. Therefore, the effect of position changes of the control point used in the horizontal network for displacement analysis of Borobudur needs to be considered, as it affects the result for the least square adjustment of the monitoring points. Two different adjustment methods used to overcome this problem, Least square adjustment using observation model and time-variant methods. This research aims to compare the horizontal displacement analysis of Borobudur resulted from these two adjustment methods.  First by giving position correction for the control point at each epoch according to its displacement in least square adjustment using observation model. The second by computing position and velocity vector directly using time-variant method. The comparation of 2D horizontal displacement vector analysis was done by using vector velocity of 2D horizontal displacement from the analysis of the two adjustment methods on the interval displacement epochs between 2002 and 2003 and between 2002 and 2012. This research showed the vector magnitude and the accuration of the displacement from the analysis resulted from the two adjustment methods was different. The resulted of least square adjustment using observation model with correction of control point showed that there was significant increase in magnitude of displacement vector of the monitoring points. Displacement analysis between 2002 and 2003 the magnitude in average were 7.97 mm and the analysis between 2002 and 2012 were 37.78 mmwith consistent displacement direction of the both interval displacement to the northwest. The Time-Variant adjustment method showed an increase in the vector velocity of 2D horizontal displacement from 0.29 mm/year to 0.32 mm/year with different displacement direction. The vector magnitude of the displacement from time variant method was smaller than observation model and the standard deviation for the horizontal displacement from time variant method was slightly bigger about 0.5 mm compared to the observation model.
Time Variant Adjustment for The Solution of Control Point Unstability in Deformation Analysis of Borobudur Vertical Deformation Monitoring Network Dwi Lestari; Yulaikhah Yulaikhah; Rizki Iman Sari
Jurnal Geospasial Indonesia Vol 1, No 1 (2018): June
Publisher : Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jgise.38590

Abstract

Borobudur is Indonesian's cultural heritage which is recognized as a world heritage by UNESCO. As a world heritage structure, monitoring and maintenance have to be carried out periodically at Borobudur. Monitoring the vertical deformation of the temple using Geodetic method is one kind of monitoring which have to be done, in this case the monitoring uses leveling network. The design of leveling network at Borobudur in 2002 used absolute network, but the control point of this network has been indicated to be shifted. The control point displacement would cause a systematic error in the adjustment computation method for the analysis of vertical displacement. The correction of control point elevation due to the vertical shift is needed prior to the adjustment computation using observation model. In addition, there is a time variant adjustment computation method which able to calculate the vertical rate of object point displacement. This study aims to compare the vertical displacement analysis of the Borobudur’s vertical network from the adjustment computation using observation model with the correction of control point height and from time-variant adjustment method.Data used in this study were the elevation differences from leveling measurements in 2002, 2003 and 2004, and the elevation and vertical velocity of the control point in 2002. Adjustment computation using observation model began with the elevation correction of control point at each epoch. The adjustment computation was taken to determine the elevation of monitoring points at each epoch. Statistical test and vertical displacement analysis using significance parameter tests was carried out to analyze the results. Adjustment computation using time-variant method was taken to determine the elevation and the vertical velocity of the monitoring points at certain epoch intervals and validated using global test after the adjustment computation.The vertical displacement magnitude of Borobudur’s monitoring points, resulted from the parameter adjustment computation with the correction of control point compared to the time-variant adjustment results was differed in nanometer.  Time-variant adjustment computation method gave more accurates result of 1.5 times better than the observation model.
GPS Technology Implementation for Sangihe Islands' Movement Monitoring in 2017-2019 Hilmiyati Ulinnuha; Dwi Lestari; Leni Sophia Heliani; Nurrohmat Widjajanti; Cecep Pratama; Parseno Parseno; Krishna Fitranto Nugroho
Jurnal Geospasial Indonesia Vol 2, No 2 (2019): December
Publisher : Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jgise.51033

Abstract

Sangihe Islands belong to a complex tectonic area at the subduction of the Eurasian plate and the Philippine Sea. Sangihe subduction zones are complex subduction zone, so that there is a need for continuous movement monitoring. Previous research had been carried out to monitor movement of the Sangihe subduction zone, but no monitoring has been done in 2019. Therefore, this study aims to monitor movement of Sangihe subduction zones with the latest observation data.This study aims to obtain velocity of Sangihe Islands plate movement during 2017 to 2019. Observation was performed using 3 monitoring control points for 7 days in 2019. While observation data from 2017 to 2018 were obtained from previous studies. Observations was carried out using GNSS differential method technology. Loosely constrained of weighted parameter was performed in least square adjustment of GNSS data daily processing, while Kalman Filtering algorithm applied for combining multiyear GNSS data to estimate the velocity refer to ITRF 2014 using GAMIT/GLOBK.This study indicates that Sangihe Islands has horizontal movement to the Southeast with velocity vector of 1 to 2.16 cm/year. This results confirm the previous studies in that area.