雷達影像多時處理研究

Study of Multi-temporal Processing of SAR Imagery

王志添(C. T. Wang) ； 陳錕山(K. S. Chen)

《航測及遙測學刊》 8卷1期 (2003/03) Pp. 47-56

https://doi.org/10.6574/JPRS.2003.8(1).4

摘要

就合成孔徑雷達(SAR)影像觀點而言，因為雷達波同調的干涉現象所引起的斑駁雜訊常使得SAR影像在應用上受到相當之限制。因此，必須有效地對斑駁雜訊加以濾除或降低以提昇SAR影像之判斷力，通常的作法是以空間平均以提高影像之有效觀點數，但也無可避免地犧牲了空間解析力。在此我們以一時序列影像先作幾何套疊並引進統計模式在不改變區域平均值的約制條件下家將訊號雜訊比最佳化。作法為將訊號在不同時間下分別求取各區域平均值，作為於時間軸上之權重，同時處理此多張影像。利用中央大學太遙中心於1998年接收歐洲太空總署ERS-2衛星於臺灣高屏地區不同時間獲取之六張SAR影像作測試。處理後發現其等效觀點數可由原來約4觀點數大幅提升至約20觀點數，除有效減抑斑駁雜訊，改善原有單張SAR影像之輻射品質外，由其空間相關係數顯示處理後之影像仍保有原空間之解析力。

關鍵字

合成孔徑雷達 ； 多時處理 ； 斑駁雜訊 ； 等效觀點數

並列摘要

Synthetic Aperture Radar (SAR) is a microwave sensor that can penetrate the clouds and rains. It can be operated day and night, because it provides its own illumination. Consequently , such a sensor bears numerous advantages for remote sensing applications. But a SAR generates the images by coherently processing the backscattered signals. ,hence, they are highly susceptible to the speckle noise. The speckle substantially reduces the effectiveness of image interpretation and target recognition. To reduce the speckle level , while maintain the spatial resolution, in this paper, we use a set of multi-temporal ERS-2 SAR images. The six scenes of different dates were first co-registered with minimal geometric shift error. By taking the time-space correlation properties, a temporal filter is used by means of multivariate analysis. We found that the equivalent number of looks (ENL) of the resulting image is improved from 4 to 20. The process of multi-temporal process greatly enhances the capability of land cover classification and change detection using SAR image.

並列關鍵字

Synthetic Aperture Radar SAR ； Multi-temporal Processing ； speckle noise ； Equivalent number of looks ENL