地層下陷最常發生在市區，而此災害可能導致建築物破裂或河水氾濫甚至改變河流的河道。儘管有精確的資訊顯示地層下陷的重要性，然而傳統的井下地層下陷監測技術，除了技術上較昂貴，也耗費人力與資源，更缺乏大範圍全面性的地層下陷資訊。近年來，SAR衛星影像干涉技術已經廣泛應用於監測地表變形，尤其是基於多時序的影像數據分析方法，在本研究中，我們使用ALOS衛星影像(L波段)多時序分析法 ，共18幅衛星影像來監測越南胡志明市於2006年12月至2010年12月期間之地層下陷的情形，因此我們應用時序影像持續監測與測量越南胡志明市的下陷情形。假設測量的結果主要是對應於垂直分量的下陷量，我們發現下陷區域沿著西貢河與市中心的南部最為顯著。最大下陷速率可達-66毫米/年。總而言之，雷達差分干涉技術的結果比對水準資料可得到相當高的一致性。;Land subsidence has become the most common hazard in urban area that could lead to cracking buildings and infrastructures, extending the flooding area or even change the river path. Despite deriving precise information, conventional subsidence monitoring techniques are considered as costly, man-power consuming and lack of comprehensive information. Recently, Interferometric synthetic aperture radar (InSAR) has become a widely used geodetic technique for monitoring the deformation of the Earth’s surface, especially methods based on the use of a multi-temporal dataset. In this study, we used a stack of 18 SAR images acquired from L-band PALSAR sensor on board the ALOS satellite to derive the subsidence information of Ho Chi Minh City, Vietnam over the period of December 2006 to December 2010. The Stanford Method for Persistent Scatterers (StaMPS) Multi-Temporal Interferometry (MTI) approach is chosen to take advantages of both the persistent scatterers and the distributed scatterers, which could be used as monitoring points to measure the subsidence process. Assume the subsidence in this area mostly corresponds to vertical components, we found subsidence patterns along Saigon River and in the South of the city. Maximum subsidence rate reaches up to -66 mm/year in vertical direction. Finally, InSAR derived result and previous levelling data are taken into comparison to find the correlation between the two results.
