Korean Journal of Remote Sensing (대한원격탐사학회지)

Korean Society of Remote Sensing (대한원격탐사학회)
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Speckle Noise Removal by Rank-ordered Differences Diffusion Filter

순위 차 확산 필터를 이용한 스페클 잡음 제거

  • Ye, Chul-Soo (School of Computer Science, Information and Standard, Far East University)
  • 예철수 (극동대학교 컴퓨터정보표준학부)
  • Published : 2009.02.28
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Abstract

The purposes of this paper are to present a selection method of neighboring pixels whose local statistics are similar to the center pixel and combine the selection result with mean curvature diffusion filter to reduce noises in remote sensed imagery. The order of selection of neighboring pixels is critical, especially for finding a pixel belonging to the homogeneous region, since the statistics of the homogeneous region vary according to the selection order. An effective strategy for selecting neighboring pixels, which uses rank-order differences vector obtained by computing the intensity differences between the center pixel and neighboring pixels and arranging them in ascending order, is proposed in this paper. By using region growing method, we divide the elements of the rank-ordered differences vector into two groups, homogeneous rank-ordered differences vector and outlier rank-ordered differences vector. The mean curvature diffusion filter is combined with a line process, which chooses selectively diffusion coefficient of the neighboring pixels belonging into homogeneous rank-ordered differences vector. Experimental results using an aerial image and a TerraSAR-X satellite image showed that the proposed method reduced more efficiently noises than some conventional adaptive filters using all neighboring pixels in updating the center pixel.

본 논문의 목적은 원격 탐사 영상에서 잡음을 제거하기 위해 중심 화소와 통계적으로 유사한 이웃화소들을 선택하늘 방법을 제시하고 이 결과를 평균 곡률 확산과 결합하는 방법을 제시하는데 있다. 균일한 밝기값 영역에 속하는 화소들을 검출하기 위해 이웃 화소들을 순차적으로 선택할 때 그 선택하는 순서에 따라 선택된 영역의 통계적 특성이 달라지므로 이웃 화소의 선택 순서는 매우 중요하다. 본 논문에서는 통계적으로 유사한 특성을 가지는 이웃 화소를 선택하기 위해서 중심 화소와 이웃 화소의 밝기값 차를 계산하고 이를 크기 순으로 정렬하여 얻어지는 순위 차 벡터(rank-ordered differences vector)를 이용하는 효과적인 방법을 제안한다. 순위 차 벡터의 항들을 영역 확장 방법을 이용하여 균일 순위 차 벡터(homogeneous rank-ordered differences vector)와 이상점 순위 차 벡터 (outlier rank-ordered differences vector)로 분할한다. 균일 순위 차 벡터의 항에 속하는 이웃 화소에 대해서만 중심 화소의 밝기값 갱신에 기여하도록 확산 계수를 선택적으로 할당하는 라인 프로세스를 평균 곡률 확산에 결합한다. 제안한 방법은 모든 이웃 화소를 이용하여 중심 화소의 밝기값을 갱신하는 기존의 잡음 제거 필터에 비해 잡음 제거 효과가 뛰어남을 항공 영상 및 TerraSAR-X 위성 영상을 이용한 실험을 통해 확인하였다.

Keywords

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