Integration PS-InSAR and MODIS PWV Data to Monitor Land Subsidence in Semarang City 2015–2018

Abstract

Land Subsidence is a slow on set disaster that can be found in coastal areas such as Semarang City. The cause is changing natural conditions and human activities. The observation method that is often done for this phenomenon is GNSS observation. The GNSS observations do not cover the entire area are the disadvantages of this method. Solution that can be used is to use a multi-temporal Interferometric Synthetic Aperture Radar (InSAR) method called Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR). In its application, PS-InSAR has a problem in the form of tropospheric errors that cause signal interference on SAR sensors when making acquisitions that contained in every Synthetic Aperture Radar (SAR) image. MODIS with the NIR band provide Precipitable Water Vapor (PWV) to estimate water vapor levels in the atmosphere. This component can be used in the PS-InSAR in order to eliminate the tropospheric effect on each image so that errors can be minimized and optimize the work of the PS-InSAR method. Based on the value of PS-InSAR before and after tropospheric correction, it is known that the area of Semarang City experienced a rate of land subsidence and the rate of uplift. Land subsidence rate occurs along the northern region, northeast to the east of Semarang City. Uplift rate only occurs in the southeast region due to dumping excavation activities for development and Banjir Kanal Barat due to the river revitalization process. Overall, Semarang City has experienced a land subsidence from 0 to 6.753 cm/year.