利用Landsae ETM+熱波段影像於災害後復健狀況評估

Evaluating the Restoring Conditions for Those Areas Visited with Natural Disasters with Employing Landsat ETM+Thermal Infrared Data

謝啟文(Wen HsiehChi)

指導教授 ： 黃怡碩

朝陽科技大學/理工學院/營建工程系/碩士(2011年)

摘要

如何有效地評估災害後重建情況，一直是防災上重要且容易被忽略的研究課題。隨著環境變遷與溫室效應的影響，自然災害侵襲台灣已成為定規，幾乎已成為每年必定上演的戲碼；防災單位多著重災情調查與事前防災策略的擬定與執行，鮮少作後續的災後重建評估，以致常無法有效地提供重建情形的量化指標，供執政者評估災後重建情況。為了解決此一問題，利用遙感探測，則提供一有效的評估方法。地表表面溫度(Land Surface Temperature, LST)可以用來表示地上人口聚集的多寡；當人口聚集越多時，該區域的地表溫度也會隨之增高，形成熱景緻型態(Thermal Landscape Pattern, TLP)。相較於鄰近具有植被或親水區域，地表溫度在都市或人口密集的區域會有較高的數值。Landsat ETM+所提供熱影像，藉著影像數值的轉換，可將影像數值轉換成地表溫度，藉以評估地表溫度變化的趨勢。本文利用Landsat ETM+ 所獲得的熱影像，將像素數值轉換成地表表面溫度，藉著多重水平集將地表面溫度根據事前決定的層級與予分析，使得區域地表溫度分佈特徵能夠被有效地分類表示；利用比較分析災前與災後地表溫度的空間分佈模式，決定災後重建的情況。本文採用四幅2009年2月24日、5月31日、9月4日及12月9日的Landsat 7 SLC-off衛星影像 ，針對台灣中部陳有蘭溪流域在莫拉克颱風侵襲前後，進行地表表面溫度分佈模式分析，建立地表表面的溫度分佈空間模式。

關鍵字

災害後重建 ； 多重水平集 ； 地表溫度

並列摘要

Evaluating the restoration conditions for those areas affected by natural disasters is an important research issue in disaster prevention and protection programs. The issue needs to simultaneously evaluate the hardware (the restored conditions for the physical environment) as well as the software (the restored conditions for psychical development). This thesis focuses on evaluating the hardware restoration conditions using the thermal infrared remote sensing. In this thesis, the study area lies between the longitudes of - E and latitudes of - N, and is an area prone to typhoon attacks. The studied area suffered serious damage from Typhoon Morakot on 2009/08/08. Landsat-7 ETM+ SLC-Off scenes collected on 2009/2/24,2009/05/31,2009/09/04 and 2009/12/09, were used to generate land surface temperature (LST) images. By employing the multilayer level set approach to segment the given LST images, landscape patterns for the study on different dates were identified and compared, in order to evaluate the time required for the landscape patterns to return to their original states. The multilayer level set approach employs two implicit functions with pre-selected level values. Based on the fact that the segmented regions are homogeneous and presented as regional constants, the energy defined by the segmented regions and their corresponding regional boundaries is minimized such that the relationships between the defined energy and the implicit functions can be transformed into the relationships between the implicit functions and time. By implementing the algorithm in terms of finite difference, this method offers an efficient and stable approach to a numerical solution. By increasing iterations and preselected level values, the implicit functions evolve close to the regional boundaries based on the energy minimization. This thesis demonstrates that the generated LST scenes can provide the opportunity for better understanding the land surface characteristics and landscape patterns, especially for those areas visited with natural disasters.

並列關鍵字

Land Surface Temperature ； Level Set Approach ； Thermal Infrared

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