Unsupervised Change Detection in Multitemporal SAR Images Using MRF Models     

JIANG Liming LIAO Mingsheng ZHANG Lu LIN Hui 《地球空间信息科学学报》2007,10(2):111-116

An unsupervised change-detection method that considers the spatial contextual information in a log-ratio difference image generated from multitemporal SAR images is proposed. A Markov random filed (MRF) model is particularly employed to exploit statistical spatial correlation of intensity levels among neighboring pixels. Under the assumption of the independency of pixels and mixed Gaussian distribution in the log-ratio difference image, a stochastic and iterative EM-MPM change-detection algorithm based on an MRF model is developed. The EM-MPM algorithm is based on a maximiser of posterior marginals (MPM) algorithm for image segmentation and an expectation-maximum (EM) algorithm for parameter estimation in a completely automatic way. The experiment results obtained on multitemporal ERS-2 SAR images show the effectiveness of the proposed method.  相似文献   

基于二进小波变换的SAR图像湖岸线提取   总被引：4，自引：1，他引：4  

范典  郭华东  岳焕印  王长林 《遥感学报》2002,6(6):511-516

本文阐述了一种基于二进小波变换的从SAR图像中提取湖岸线的方法。该方法首先利用边缘和噪声的奇异性在二进小波变换中随尺度变化具有不同的传播规律来检测边缘点，然后利用基于梯度矢量流的主动轮廓模型进行边缘点的连接，实验结果证明，这种方法可以有效的消除SAR图像中存在的斑点噪声对边缘提取的影响，准确的提取湖岸线。  相似文献   

白令海与西北冰洋表层沉积物中四醚膜类脂物研究及其生态和环境指示意义     

王寿刚  王汝建  陈建芳  陈志华  程振波  汪卫国  黄元辉 《地球科学进展》2013,28(2):282-295

通过对中国第3次和第4次北极考察在白令海和西北冰洋采集的65个表层样沉积物中生物标记物四醚膜类脂物(GDGTs)的研究,发现西北冰洋表层沉积物中类异戊二烯和支链GDGTs的浓度分布大致以楚科奇海和波弗特海的陆坡为界线,呈现南高北低的特征,这一特征主要与水体生产力和陆源有机质的输入量有关.基于GDGTs的陆源输入指数BIT显示,从楚科奇海北部到高纬度区的阿尔法脊,陆源有机质的相对比例明显增加,与有机碳稳定同位素等结果一致,表明BIT可以用来指示北极陆源有机质输入量的变化.应用前人TEXL86-SST方程估算的研究区表面海水温度SST与现代年均SST和夏季平均SST的相关性较差,原因可能与陆源输入的类异戊二烯GDGTs干扰以及低的古菌生产力有关.从季节性海冰覆盖区到永久性海冰覆盖区,基于支链GDGTs的环化指数CBT明显升高,可能反映了CBT对海冰覆盖状况的响应,但其响应机制还不清楚.基于支链GDGTs的环化指数CBT和甲基化指数MBT估算的北极陆地年均大气温度和土壤pH差异较大,可能是由表层沉积物的来源复杂以及混合作用造成的.  相似文献   

A search for magnetic fields in cool sdB stars     

G. Mathys  S. Hubrig  E. Mason  G. Michaud  M. Schller  F. Wesemael 《Astronomische Nachrichten》2012,333(1):30-33

Hot cluster horizontal branch (HB) stars and field subdwarf B (sdB) stars are core helium burning stars that exhibit abundance anomalies that are believed to be due to atomic diffusion. Diffusion can be effective in these stars because they are slowly rotating. In particular, the slow rotation of the hot HB stars (T_eff > 11000 K), which show abundance anomalies, contrasts with the fast rotation of the cool HB stars, where the observed abundances are consistent with those of red giants belonging to the same cluster. The reason why sdB stars and hot HB stars are rotating slowly is unknown. In order to assess the possible role of magnetic fields on abundances and rotation, we investigated the occurrence of such fields in sdB stars with T_eff < 30 000 K, whose temperatures overlap with those of the hot HB stars. We conclude that large‐scale organised magnetic fields of kG order are not generally present in these stars but at the achieved accuracy, the possibility that they have fields of a few hundred Gauss remains open. We report the marginal detection of such a field in SB 290; further observations are needed to confirm it (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Log-cumulants of the finite mixture model and their application to statistical analysis of fully polarimetric UAVSAR data     

Xinping Deng  Hongzhong Li  Pengpeng Han  Wen Yang 《地球空间信息科学学报》2018,21(1):45-55

Since its first flight in 2007, the UAVSAR instrument of NASA has acquired a large number of fully Polarimetric SAR (PolSAR) data in very high spatial resolution. It is possible to observe small spatial features in this type of data, offering the opportunity to explore structures in the images. In general, the structured scenes would present multimodal or spiky histograms. The finite mixture model has great advantages in modeling data with irregular histograms. In this paper, a type of important statistics called log-cumulants, which could be used to design parameter estimator or goodness-of-fit tests, are derived for the finite mixture model. They are compared with log-cumulants of the texture models. The results are adopted to UAVSAR data analysis to determine which model is better for different land types.  相似文献   

干盐湖区隐伏控卤构造遥感识别研究——以马海盐湖为例     

姚佛军  焦鹏程  赵艳军  赵宪福  张华  刘成林 《地质学报》2021,95(7):2225-2237

马海盐湖是柴达木盆地一个重要的成钾盐湖,本研究对该盐湖区隐伏控卤构造开展遥感识别研究,利用LANDSAT光学遥感数据和PALSAR雷达遥感数据,采用了光学遥感假彩色合成影像解译和雷达遥感数据干涉分析,解译了研究区的构造,识别出研究区一级构造三条,二级的构造若干条.并通过在干盐湖区遥感构造识别及构造应力分析,判定了2条一级压性构造和1条一级张性构造,对解译的构造进行野外查证,压性构造和张性构造野外特征明显,同时受构造几何形态影响,同一断裂不同部位断裂性质会发生变化,张性应力的位置除与构造性质有关外,也与构造几何特征有关,并进行了野外查证.本次研究结合已知卤水矿和浅表给水度和含钾率的分析,最终圈定出两个具有潜力的遥感预测靶区.  相似文献   

利用SAR遥感卫星资料研究东海内孤立波时空分布特征     

郭靖  杜涛 《海洋预报》2014,31(5)

通过分析欧洲空间局的地球资源卫星(ERS-1/2)从1995—2010年的合成孔径雷达(SAR)图像,研究了东海内孤立波的时间分布特征,绘制了东海内孤立波的空间分布图,并且反演了个别海区内孤立波的传播速度。研究结果表明:东海内孤立波主要分布在两个海域,台湾东北部海域和长江口、杭州湾以及外舟山群岛附近海域。在这两个海域,大潮期间的强潮流有利于内孤立波的出现。在长江口及附近海域,跃层强时,内孤立波出现的概率相对较高。台湾东北部内孤立波波速约为0.6—0.8 m/s,长江口及附近海域内孤立波波速约为0.6 m/s左右。  相似文献   

大地水准面高对InSAR大范围地壳形变监测的影响分析   总被引：1，自引：0，他引：1       下载免费PDF全文

李鹏  李振洪  施闯  冯万鹏  梁存任  李陶  曾琪明  刘经南 《地球物理学报》2013,56(6):1857-1867

由于InSAR数据处理所用的WGS84参考椭球系统与通用的DEM高程系统(EGM96大地水准参考面)不一致,在InSAR形变监测分析中会引入大地水准面高导致的误差.本文利用覆盖青藏高原北部阿尔金断裂带西段的27景Envisat ASAR宽幅模式数据和44景条带模式数据,研究了大地水准面高与InSAR大范围形变测量不确定性的关系:(1)模拟分析表明对于100 m的垂直基线,8.8 m的DEM测量误差,若研究区域存在20 m的大地水准面高的变化,对宽幅或条带模式InSAR形变测量造成的影响将由3 mm增至10 mm左右;(2)实例验证表明对于不同的研究区域,大地水准面高与该地区地形变化存在较大相关性,对于同一研究区域,垂直基线的大小决定了大地水准面高对InSAR不确定性的影响程度;(3)对于大地水准面高有较大梯度变化的研究区域,组合短基线方法与去除轨道平面的方法难以消除大地水准面高的影响.使用基于WGS84高程系统的DEM,可以为InSAR形变测量分析提供统一的高程基准,有效避免大地水准面高误差的影响.  相似文献   

Sr isotope geochemistry and Pb–Pb geochronology of the Neoproterozoic cap carbonates,Tangará da Serra,Brazil     

《International Geology Review》2012,54(2):185-203

  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987111001332   总被引：1，自引：1，他引：0  

Liu He  Chuanlun L. Zhang  Hailiang Dong  Bin Fang  Genhou Wang 《地学前缘(英文版)》2012,3(3):289-300

Isoprenoidal glycerol dialkyl glycerol tetraethers（iGDGTs） from the Gulu hot springs （23-83.6℃,pH>7） and Yangbajing hot springs（80—128℃,pH>7） were analyzed in order to investigate the distribution of archaeal lipids among different hot springs in Tibet.A soil sample from Gulu was incubated at different temperatures and analyzed for changes in iGDGTs to help evaluate whether surrounding soil may contribute to the iGDGTs in hot springs.The sources of bacterial GDGTs（bGDGTs） in these hot springs were also investigated.The results revealed different profiles of iGDGTs between Gulu and Yangbajing hot springs. Core iGDGTs and polar iGDGTs also presented different patterns in each hot spring.The PCA analysis showed that the structure of polar iGDGTs can be explained by three factors and suggested multiple sources of these compounds.Bivariate correlation analysis showed significant positive correlations between polar and core bGDGTs.suggesting the in situ production of bGDGTs in the hot springs.Furthermore,in the soil incubation experiment,temperature had the most significant influence on concentration of bGDGTs rather than iGDGTs.and polar bGDGTs had greater variability than core bGDGTs with changing temperature.Our results indicated that soil input had little influence on the composition of GDGTs in Tibetan hot springs. On the other hand,ring index and TEX₈₆ values were both positively correlated with incubation temperature, suggesting that the structure of archaeal lipids changed in response to varying temperature during incubation.  相似文献