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An automatic detection of green tide using multi-windows with their adaptive threshold from Landsat TM/ETM plus image 被引量:4
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作者 WANG Changying CHU Jialan +3 位作者 TAN Meng SHAO Fengjing SUI Yi LI Shujing 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2017年第11期106-114,共9页
Since the atmospheric correction is a necessary preprocessing step of remote sensing image before detecting green tide, the introduced error directly affects the detection precision. Therefore, the detection method of... Since the atmospheric correction is a necessary preprocessing step of remote sensing image before detecting green tide, the introduced error directly affects the detection precision. Therefore, the detection method of green tide is presented from Landsat TM/ETM plus image which needs not the atmospheric correction. In order to achieve an automatic detection of green tide, a linear relationship(y =0.723 x+0.504) between detection threshold y and subtraction x(x=λnir–λred) is found from the comparing Landsat TM/ETM plus image with the field surveys.Using this relationship, green tide patches can be detected automatically from Landsat TM/ETM plus image.Considering there is brightness difference between different regions in an image, the image will be divided into a plurality of windows(sub-images) with a same size firstly, and then each window will be detected using an adaptive detection threshold determined according to the discovered linear relationship. It is found that big errors will appear in some windows, such as those covered by clouds seriously. To solve this problem, the moving step k of windows is proposed to be less than the window width n. Using this mechanism, most pixels will be detected[n/k]×[n/k] times except the boundary pixels, then every pixel will be assigned the final class(green tide or sea water) according to majority rule voting strategy. It can be seen from the experiments, the proposed detection method using multi-windows and their adaptive thresholds can detect green tide from Landsat TM/ETM plus image automatically. Meanwhile, it avoids the reliance on the accurate atmospheric correction. 展开更多
关键词 automatic detection green tide adaptive threshold Landsat TM/etm plus image
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Glacier Extent and Volume Change(1966~2000) on the Su-lo Mountain in Northeastern Tibetan Plateau,China 被引量:10
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作者 WANG Yetang HOU Shugui +2 位作者 HONG Sungmin HUR Soon Do LIU Yaping 《Journal of Mountain Science》 SCIE CSCD 2008年第4期299-309,共11页
The topographic maps of 1:50,000 scales,aerial photographs taken in 1966,one Landsat image taken in 1999,and SRTM data from 2000 were used to quantify the losses in area and volume of the glaciers on the Su-lo Mountai... The topographic maps of 1:50,000 scales,aerial photographs taken in 1966,one Landsat image taken in 1999,and SRTM data from 2000 were used to quantify the losses in area and volume of the glaciers on the Su-lo Mountain,in the northeastern Tibetan Plateau,China in the past 30 years.The total glacier area decreased from 492.9km2 in 1966 to 458.2km2 in 1999.The volume loss of the studied glaciers reached 1.4 km3 from 1966 to 2000.This agrees with documented changes in other mountain glaciers of the whole Tibetan Plateau. 展开更多
关键词 Glacier change Su-lo Mountain etm image Tibetan Plateau China
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