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Pages : 51-69    高時空融合影像在氣膠光學厚度反演之應用
論文名稱 高時空融合影像在氣膠光學厚度反演之應用
Title AOD Retrieval with High Temporal and Spatial Fused Imagery for Regional Air Quality Monitor
作者 郭人維、黃智遠、張國恩、林唐煌、劉振榮
Author Ren-Wei Kuo, Chih-Yuan Huang, Kuo-En Chang, Tang-Huang Lin, Gin-Rong Liu
中文摘要 為獲取高時空解析之氣膠資訊,本研究針對自適應時空反射率融合模式 (STARFM) 於大氣層頂反射率之影像融合進行修正,並利用同時輻射率定法 (SRS) 反演氣膠光學厚度 (AOD),最後應用於地球同步 (Himawari-8) 與繞極軌道 (Landsat-8) 衛星影像在台灣地區空氣污染事件高時空解析之監測,結果以MODIS AOD產品和AERONET 地面觀測AOD,分別對大氣氣膠空間分布型態和AOD反演數值進行驗證,結果顯示本研究所反演之AOD與MODIS AOD在空間分布型態相當吻合,且反演數值在兩個案中分別有63%及80%的期望誤差內,呈現本研究所建構之方法在衛星反演高時空解析氣膠光學厚度,具極高之實用性及後續在PM2.5監測應用之潛能。
Abstract Aerosol Optical Depth (AOD) is an important indicator of air quality. Through satellite observation, we can obtain comprehensive information on AOD in broad spatial distribution. Since the characteristics of aerosols are both short-lived and regional, the research aim to revise the Spatial-Temporal Adaptive Reflectance Fusion Model (STARFM) to get high spatial and temporal resolution images at top of atmosphere. Moreover, we use an algorithm called Simultaneous Radiation Solution (SRS) to retrieve AOD. To correct the limitation of SRS, which is only applicable for low surface reflectance area, we modify the SRS in this research and further apply it on a higher surface reflectance area. In short, we get high spatial and temporal AOD information through STARFM and SRS. After applying the improved high spatial and temporal algorithm on air pollution events in Taiwan, the result shows well consistence of spatial distribution with MODIS Dark Target AOD product in 3km resolution and similar trend with AOD retrieved from ground based AERONET data. The validation of AOD retrievals showed that there are 63% and 80% of retrieved AOD for each case located in expected error respectively. It indicates that the proposed approach equips with the high potential for providing AOD with both high spatial resolution and high temporal resolution from satellite observations.
關鍵字 高時空影像融合、自適應時空反射率融合模式 (STARFM)、氣膠光學厚度(AOD)、同時輻射率定法 (SRS)
Keywords Image Fusion, Spatial Temporal Adaptive Reflectance Fusion Model (STARFM), Aerosol Optical Depth (AOD), Simultaneous Radiation Solution (SRS)
Pages : 71-86    優化魚眼鏡頭率定
論文名稱 優化魚眼鏡頭率定
Title Optimization of Fisheye Lens Calibration
作者 楊軒、趙鍵哲
Author Hsuan Yang, Jen-Jer Jaw
中文摘要 本研究為後續高精度 (前方交會誤差毫米等級,或小於地面取樣距離) 空間定位應用需求,採用基於魚眼投影幾何所推導出的物像對應模式搭配附加參數吸納透鏡畸變差。本篇文章主要著眼於魚眼鏡頭率定觀測資料蒐集面工作之優化,經實驗證實,於率定場中布設20個分布良好的率定標點以及位置適中的兩攝影站,並採用自率光束法搭配次像元像點與毫米級控制點觀測量,即可達至次像元之後驗單位權標準差 (0.24 pixels) 與前方交會誤差毫米級 (<5.6 mm,反投影約0.5 pixels) 之率定成果,顯示本研究方法及程序能有效及精準執行魚眼鏡頭率定,同時,物像對應品質亦足夠支援次像元等級的物空間定位應用。
Abstract Since the fisheye lens has its own specific type of imaging formation, using collinearity equation attached by additional lens distortion parameters cannot set up a sufficient model. To achieve the relevant requirements of the metric measurement, this study adopts the rigorous object-image corresponding model to include geometric projection model for fisheye lens calibration. The discrepancy between the ideal image point and the actual image point is treated as the effect of lens distortion and modeled by additional parameters. This study aims to tackle effective implementation. It is revealed from the experimental results that the object-to-image correspondence of fisheye lens based on the proposed model offers satisfactory geometric calibration quality. Strategically, the bundle adjustment with self-calibration for fisheye lens can be realized under sub-pixel image measurement quality at the expense of only 20 well-distributed coded targets and acquiring two images at appropriate locations to achieve the sub-pixel level of object point positioning. Thus, it is verified that the proposed methods and procedures can effectively and accurately implement the fisheye lens calibration. At the same time, the calibration result is also sufficient to support the mission of object point determination up to sub-pixel level quality.
關鍵字 魚眼鏡頭、透鏡畸變、幾何投影、自率光束法、內部約制
Keywords Fisheye lens, Lens distortion, Geometric projection, Bundle adjustment with self-calibration, Inner constraint
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