LAND SUBSIDENCE STUDY USING GEODETICS GPS AND GAMIT/GLOBK SOFTWARE (Case Study : Banjarasri Village and Kedungbanteng Village, Tanggulangin District, Sidoarjo Regency)

Banjir merupakan salah satu bencana alam yang selalu terjadi di berbagai Wilayah Negara Kesatuan Republik Indonesia. Tercatat beberapa titik banjir terjadi di Desa Banjarasri dan Desa Kedungbanteng, Kecamatan Tanggulangin, Kabupaten Sidoarjo. Terdapat dugaan bahwa salah satu faktor penyebab banjir di kedua desa tersebut disebabkan oleh adanya penurunan tanah (land subsidence). Oleh karena itu, perlu dilakukan studi untuk memantau besarnya penurunan tanah di kawasan tersebut. Dalam penelitian ini digunakan metode pengamatan Global Positioning System (GPS). Penelitian dilakukan dengan pengambilan data sebanyak enam titik yang dilakukan selama tiga kala kala, yaitu pada tanggal pada 22 – 27 Oktober 2020, 24 - 29 November 2020, dan 24 – 29 Maret 2021. Berdasarkan hasil pengolahan dan analisis data GPS, diperoleh nilai pergeseran dan pergerakan vektor pengamatan. Tercatat lima titik mengalami penurunan tanah secara signifikan yang meliputi BM02, BM03, BM04, BM05, dan BM06 dengan nilai masing-masing sebesar 3,6 cm, 7,3 cm. 5,9 cm, 4,8 cm, dan 5,2 cm. Vektor pergerakan lokal posisi horisontal bergerak secara beragam dimana BM01 dan BM04 mengalami pergerakan ke\ud arah barat daya dengan pergeseran 2,5 cm dan 1,4 cm, BM 02 dan BM03 bergerak ke arah barat laut dengan pergeseran 1,0 cm vi dan 1,3 cm, BM05 bergerak ke arah tenggara dengan pergeseran 2,5 cm, dan BM06 bergerak ke arah timur laut dengan pergeseran sebesar 3,8 cm. Kata Kunci—GPS, Deformasi, Penurunan Tanah ================================================================================================================== Floods are one of the natural disasters that always occur in various regions in the Republic of Indonesia. Several flood points were recorded in Banjarasri Village and Kedungbanteng Village, Tanggulangin District, Sidoarjo Regency. There is an allegation that one of the factors causing the flooding in the two villages was caused by land subsidence. Therefore, it is necessary to conduct a study to monitor the magnitude of land subsidence in the area. In this study, the Global Positioning System (GPS) observation method was used. The research was carried out by collecting data from six points which were carried out over three periods of time, namely on 22 – 27 October 2020, 24 – 29 November 2020, and 24 – 29 March 2021. Based on the results of processing and analyzing GPS data, the observed values for shift and motion vectors are obtained. Five points that experienced significant land subsidence, including BM02, BM03, BM04, BM05, and BM06 with values of 3.6 cm, 7.3 cm, 5.9 cm, 4.8 cm, and 5.2, cm respectively. The local movement vectors of horizontal positions move in various ways, where BM01 and BM04 move to the southwest with a displacement of 2.5 cm and 1.4 cm, BM 02 and BM03 move to the northwest with a displacement of 1.0 cm and 1.3 cm, BM05 moves to the southeast viii with a displacement of 2.5 cm, and BM06 moves to the northeast with a displacement of 3.8 cm. Keywords —GPS, Deformation, Land Subsidenc