Josaphat Laboratory graduated Dr. Luhur Bayuaji with Ph.D thesis entitled “Application of differential interferometry synthetic aperture radar data to disaster monitoring” in 25 March 2009. He was staff of University of Indonesia and recipient of Monbukagakusho Scholarship to study in Josaphat Laboratory.
Abstract : Disasters, both natural and man-made, are increasing in their frequency and catastrophic impact in Indonesia. Earthquake, flood, landside, subsidence are only a few to mention. Disaster, in the true sense, always occur involving human beings, especially as victims. Due to the lack or inadequate disaster prevention and mitigation strategies in Indonesia, the impact of disasters which they do occur is much greater than in other developed countries. Disaster detection and monitoring are essential aspect in disaster mitigation and it’s conventionally done by ground survey. Nowadays, remote sensing, both in optical and radar sensor, plays important role on disaster mitigation. In tropical region such as Indonesia, data retrieved by radar sensor provide some information which hard to obtain by optical sensor. Radar interferometry is an imaging technique for measuring the geodetic information of terrain by exploiting phase information of the backscattered radar signal from ground surface to retrieve the altitude or displacement of the objects. Differential Interferometry Synthetic Aperture Radar (DInSAR) is one of well known the radar interferometry techniques that allow us to investigate surface deformation phenomena with a centimeter to millimeter accuracy and with a large spatial coverage. It has been increasing used to monitor ground surface displacements, which may be caused by various natural disasters such as earthquakes, landslides, avalanches or human activities such as mining activities, groundwater extraction, etc. Typically, ii displacement information was being collected through field measurement which has many disadvantages such as time consuming, hazardous and few point locations. This dissertation will reveal the ability and advantages of DInSAR as efficient and cost-effective method for subsidence disaster monitoring in tropical area which were caused by natural disaster and human activities. In this dissertation, DInSAR will be integrated with ground survey data and Geographic Information System (GIS) to provide better result and analysis. In the future, further development of this dissertation is to create integrated system to reinforce subsidence assessment method and mitigate potential risk to infrastructure, live and environment. The study sites in this dissertation are Jakarta, the capital city of Indonesia for urban disaster monitoring and Sidoarjo, east Java province for man-made disaster monitoring. Jakarta has serious subsidence problem which give impact to infrastructure and worsening flood impact every year. Sidoarjo experiences subsidence because of continuous and enormous volume of geological hot mud eruption which is triggered by gas exploration drilling. Both sites have similarities that the subsidences are caused by natural and human activities. The selection of suitable interferometric pairs is limited by temporal separations of the acquired SAR images as well as the characteristics of the iii site. The pairs with good coherence were selected for further processing. The coherence analysis was studied for each site. The Digital Elevation Model (DEM) data retrieved from Shuttle Radar Topography Mission were employed to remove the topographic error. Phase unwrapping process was employed in the DInSAR result. In this study the subsidence areas were retrieved and analyzed by using L-Band ALOS PALSAR data.The influence of coherence on DInSAR result also presented in this study. Atmospheric and temporal error occurred in the result were analyzed and raised the importance to increase the data availability and revisit cycle. For Sidoarjo study site, hot mud temperature distribution was investigated using TERRA ASTER data. Based on DInSAR result, simple method to estimate subsidence volume also developed in this study because volume of subsidence gives direct impact for infrastructure and environment. Subsidence direction and subsidence potential area also investigated by calculating subsidence gradient of continues monitoring. It leads to possibility on producing subsidence hazard map on investigated area. The result of this study showed that the DInSAR method was potential to monitor subsidence in urban area as well as vegetated area. The accuracy of the derived subsidence can be further improved by increasing the data availability and shorten revisit cycle. Better imaging resolution will also be iv advantage. The subsidence can be monitored at an accuracy of centimeter in the wavelength 24 cm of L-Band ALOS PALSAR.