The use of interferometric spaceborne radar and GIS to measure ground subsidence in peat soils in Indonesia

Interferometric synthetic aperture radar (InSAR) has been increasingly used to extract information about the earth‟s surface by exploiting the phase difference between two complex radar signals. Some significant application fields that utilize InSAR techniques are digital elevation model (DEM) generation, land use classification and land subsidence. In this thesis, by using ERS-1/2 tandem SAR images pairs, the potential implementations of SAR interferometry in tropical peatland forests in Central Kalimantan, Indonesia are described. Coherence was found to be a good tool for rapid assessment for burned and deforested areas. The coherence of burned forest area was increased by 0.2; whilst the minimum coherence was found to be than 0.35. However, many critical factors affect the quality of InSAR data and limit its applications, such as methods of InSAR data processing. This study emphasizes the impact of different processing and phase unwrapping techniques on DEM accuracy. Analyses of InSAR DEM accuracy indicate that DEMs with relative errors of less than 3 m root mean square error (RMSE) are possible in some regions in the former Mega Rice Project (Ex-MRP) area and could meet many objectives of a global mapping mission. Applying adaptive filtering many times with a decreasing window size has a strong impact to reduce the number of residues, which can increase the phase unwrapping efficiency and the final DEM accuracy. Furthermore, the differential SAR Interferometry (DInSAR) was examined to see if it can detect peatland subsidence accurately from October 1997 to January 2000 using 4-pass and complex interferogram combination methods. The subsidence rate of 2 cm per year is considered to be the best possible prediction for subsidence in the project area and between 53 and 83 Mt of peat carbon was lost for the same period of the study. The contribution of the maximum subsidence to the emission of CO2 was estimated to be 52 tonnes per hectare per year. These results are not reliable enough for detailed planning purposes, but they provide a basis for further work by highlighting where methodological development is needed.