| 摘要: | 近年來，隨著新的合成孔徑雷達（ SAR）衛星任務，合成孔徑雷達干涉測量（InSAR ）已成為越來越多的研究學者的有用的技術。合成孔徑雷達技術的發展已經遠遠超出原來的範圍，涵蓋了不同的目的和學術。合成孔徑雷達圖像進行了研究生物質能測繪，冰川變遷，地表土壤之分類，特別是監測地表的變形。
此外，SAR影像和技術可用於監測文化遺蹟，歷史建築和考古的變遷。相較於傳統的監測技術，利用雷達衛星遙測技術監測文化遺址有其優缺點。在主動式的監測下，這些監測可以在晝/夜或天氣狀況。可全方位監測分析並減少或避免因災害所造成的建築物損壞情形。在另一方面，SAR影像主要的限制是在於SAR衛星影像本身和SAR處理技術的過程。目前，大多數的SAR影像不適合監測小區域或高精度的地表變形，SAR處理技術主要是監測較大的地表變形模式。
在本研究中，使用高解析度與高精度的TerraSAR-X影像。為了提高監測覆蓋率和地表變形精度，我們整合最小基線長（SB）InSAR技術與多倍取樣分析來監測SAR衛星影像之地陷情形。主要研究區域在越南河內市中心的文化遺跡。
本研究結果包含了62900000個雷達影像目標偵測點，即平均密度為217012個/平方公里。我們的研究結果顯示在影像多倍採樣的分析下，不僅增加了4.4倍的高精度雷達偵測點，並且過濾掉雜訊較多與誤差較高的偵測點。本研究區域觀測到的下陷情形與大多與相鄰的地下水開採和建設活動有關，於2012年4月至2013年11月間，本研究區最大下陷速率可達到 18.1毫米/年，一般來說，在歷史文物保存區，古蹟城堡和舊城區仍然保持在一個穩定不下陷的狀態，而那些沿著紅河和河內南部的地區則分別受到地陷的影響。;Recently, with the launch of new Synthetic Aperture Radar (SAR) missions, Interferometric Synthetic Aperture Radar (InSAR) has become more and more useful tool for researchers. The developments of SAR techniques have gone far beyond the original scope, covering different disciplines. SAR imagery is now used for biomass mapping, glacier tracking, landcover classification and especially monitoring the deformation of the Earth’s surface.
SAR could be used for monitoring the stability of ancient monuments, historical buildings and archaeological sectors. Compared to traditional monitoring techniques, the use of radar remote sensing for monitoring cultural heritage sites has both advantages and disadvantages. In the positive manners, those sites could be automatically monitored regardless day/night time and weather conditions. More comprehensive pictures could be potentially derived, and damages to structures could be possibly minimized or avoided. The major limitations, on the other hand, lay on the resolution of SAR imagery and SAR processing techniques. Most of current SAR sensors are not appropriate for monitoring surface displacements at a very small scale and high precision, and SAR processing techniques primarily optimize for large deformation patterns.
In this work, the X-band TerraSAR-X imagery is used for the sake of resolution and precision. To enhance the monitoring coverage and detail, we integrated the oversampling techniques to the Small Baseline (SB) InSAR for processing SAR imagery. Test site was choosen at the Historical Centre of Hanoi, Vietnam, where the relics were left by most Vietnamese dynasties in the past, greater than any other places over the country.
A total of 6.29 million radar targets were obtained, maintaining the average density of 217,012 points/km2. Our results suggest that image oversampling not only increased the number of measurement points 4.4 times more than the standard processing chain, but also removed the noisiest points. The observed subsidence patterns are mostly related to adjacent groundwater extraction and construction activities, with maximum subsiding rate reached −18.1 mm/year for the study period from April 2012 to November 2013. Generally, heritage assets and monuments in the Citadel, the Old Quarter and French Quarter remain in a steady state, whereas those located along the Red River and in southern Hanoi were subjected to subsidence. |
