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Pages : 1-16    時頻濾波器過濾影像雜訊之效果
論文名稱 時頻濾波器過濾影像雜訊之效果
Title Time-Frequency Filters and Their Results on Image Noise Filtering
作者 紀凱屏 , 蔡展榮
Author Kay-Ping Chi , Jaan-Rong Tsay
中文摘要 本文探討各種不同的影像雜訊過濾方法,包括空間域的方法、頻率域的方法、時頻域的方法。並以影像復原概念為基礎,將五張不同類型的實驗影像分別加入隨機雜訊(如:高斯雜訊、斑駁雜訊、椒鹽雜訊)、系統性雜訊(如:相干雜訊),文末再以時頻域中的Daubechies 小波法過濾衛載合成孔徑雷達影像為例,綜合分析各法過濾影像雜訊的效果。由實驗結果可看出應用時頻域的方法過濾雜訊確實是可行的,其中,空間濾波器與 Daubechies 小波法皆能有效的過濾高斯雜訊與斑駁雜訊;椒鹽雜訊則以空間濾波器的中值濾波器效果最好;而相干雜訊的部分以頻率濾波器中的帶阻濾波器效果最好。
Abstract In this paper, we discuss different approaches for reducing image noise, including filtering image noise in spatial domain, frequency domain, and time-frequency domain, and estimate their denoising effect. We use a spaceborne SAR (=Synthetic Aperture Radar) image and add several kinds of noise in five different test images under the theoretical concepts of image restoration. They include (1) random noise such as Gaussian noise, speckle noise and salt-and-pepper noise, and (2) systematic noise such as coherent noise. The results demonstrate that Daubechies wavelet approach is efficient. Spatial filters and Daubechies wave-let approach can filter out the Gaussian and speckle noise well. Median filters are good ones for reducing salt-and-pepper noise. Bandreject filters are suitable for filtering out the coherent noise.
關鍵字 時頻濾波器、影像雜訊、影像復原、小波轉換
Keywords time-frequency filter, image noise, image restoration, wavelet transform
Pages : 17-40    以統計模式進行地形資料的融合及變遷偵測
論文名稱 以統計模式進行地形資料的融合及變遷偵測
Title Fusion of Terrain Data Sets and Change Detection by Statistical Approach
作者 黃宗仁 , 趙鍵哲
Author Tsung-Jen Huang , Jen-Jer Jaw
中文摘要 因工程需求,地形監控或災害評估等目的,地形資料之生產頻繁,故同一地區之地形資料來源廣泛(經由不同單位、不同時間測取)。儘管在點位密度、取樣位置及地形資料精度上,各資料間有所差異,其獲取地形資料而所重複投入之人力、財力卻是不爭的事實。因此從實用觀點上出發,如何有效地融合諸多「重複觀測」之地形,而衍生出一套更佳之地形估值;甚至在融合過程的歧異現象上,歸結並偵測出地形變遷的事實,據以提供政府部門或各個工程機關使用,遂成為本研究探討之重點。 地形資料融合之精義在於資料間的相互比對繼而整合,因此某些系統性的問題,例如地形變遷,便會在資料比對的過程中彰顯出來。而純屬隨機部分、穩定的地形資料便可藉助融合的處理,產生更佳的地形估值(即更佳的地形精度及可靠度)。本研究將地形視為一種訊號,為考量保留最原始資料量測精度,融合的邏輯不藉助任何型式的內插方式(除非地形可以某種數學函數描述之),不限定資料本身的型式,以統計的工具進行地形資料的融合及變遷報導。
Abstract The highly repeated observations, multi-temporal or multi-source, of terrain data for a specific area can be often seen due in great part to the purposes of civil activities, topographic monitoring and damage evaluation, etc. They may seem to vary in point density, sampling strategies and accuracy as well, though. From economic point of view, deriving a better estimation of terrain information by fusing the homogeneous terrain data sets may draw great attention both for research and practical interest. As a by-product of that, the topographic change could be also detected accordingly based on the disagreement via fusing procedures. The central principle of fusing terrain data sets stems from cross check, thereby signaling out system­atic problems such as topographic change, among them and keeping steady terrain data sets combined and resulting in an updated terrain data with better accuracy and reliability. The proposed method for fusion of terrain data sets and change detection employs the statistical approach which features in making no as­sumption of the terrain characteristics and without relying on any specific data format. The preliminary results show satisfactory performance based on the evaluations in efficiency and accuracy aspect.
關鍵字 地形變遷、融合過程、相互比對
Keywords Topographic Change, Fusing Procedures, Cross Check
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