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841.
842.
针对非下采样Contourlet变换(NSCT)在处理噪声影像中具有的优势,以及同极化SAR图像(HH、VV)之间的相关性与互补性,本文实验了一种基于非下采样Contourlet变换的极化图像融合方法。该方法首先对每个极化图像进行多尺度、多方向分解,然后对不同分解子带系数分别采用有利于斑点噪声去除和信息增强的融合规则进行融合,最终通过NSCT反变换得到融合图像。通过信息熵、相关系数以及等效视数等指标的评价,验证了该方法可以有效地实现信息增强,同时该方法也在一定程度上降低了斑点噪声的负面影响。 相似文献
843.
利用目标点最小生成树的路面裂缝检测 总被引:1,自引:0,他引:1
分析路面裂缝的成像特点,提出了一种基于目标点最小生成树的路面裂缝检测方法。最小生成树具有描述空间线性聚集特征的优点,有利于实现对裂缝的全局分析和提取。实验结果表明,对不连续裂缝的处理,本文方法优于传统方法。 相似文献
844.
机载LiDAR点云数据的建筑物重建研究 总被引:5,自引:2,他引:3
提出了利用机载LiDAR点云数据进行复杂平面建筑物重建的方法。首先,将提取出的建筑物点云聚类到不同的平面点集;然后,对各个平面点集进行平面拟合,采用平面相交确定平面边界,并解算出各平面边界角点的三维坐标,从而重建建筑物模型。某区域的机载LiDAR点云数据的实验结果表明,该方法能有效地重建出较复杂的平面建筑物。 相似文献
845.
846.
卫星导航系统基本完好性监测对象是基本导航电文,其算法模型有两种:一是用户伪距精度(URA)和实时用户距离精度(RURA);二是空间信号精度(SISA)和空间信号监测精度/完好性标示(SISMA/IF).通过对卫星导航系统基本完好性监测技术进行分析定义,研究了系统基本完好性的两种主流算法.分别在正常情况下、卫星钟差和轨道... 相似文献
847.
Kun Yang Baisheng Ye Degang Zhou Bingyi Wu Thomas Foken Jun Qin Zhaoye Zhou 《Climatic change》2011,109(3-4):517-534
The Tibetan Plateau (TP) surfaces have been experiencing an overall rapid warming and wetting while wind speed and solar radiation have been declining in the last three decades. This study investigated how climate changes influenced the hydrological cycle on the TP during 1984??2006. To facilitate the analysis, a land surface model was used to simulate surface water budget at all CMA (China Meteorological Administration) stations on the TP. The simulated results were first validated against observed ground temperature and observation-derived heat flux on the western TP and observed discharge trends on the eastern TP. The response of evaporation and runoff to the climate changes was then analyzed. Major finding are as follows. (1) Surface water balance has been changed in recent decades. Observed precipitation shows insignificant increasing trends in central TP and decreasing trends along the TP periphery while evaporation shows overall increasing trends, leading to decreased discharge at major TP water resource areas (semi-humid and humid zones in the eastern and southern TP). (2) At the annual scale, evaporation is water-limited in dry areas and energy-limited (radiation and air temperature) in wet areas; these constraints can be interpreted by the Budyko-curve. Evaporation in autumns and winters was strongly controlled by soil water storage in summers, weakening the dependence of evaporation on precipitation at seasonal scales. (3) There is a complementary effect between the simulated actual evaporation and potential evaporation, but this complementary relationship may deviate from Bouchet??s hypothesis when vapor pressure deficit (or air temperature) is too low, which suppresses the power of vapor transfer. 相似文献
848.
Bao Yang Dmitry M. Sonechkin Nina M. Datsenko Nadezda N. Ivashchenko Jingjing Liu Chun Qin 《Theoretical and Applied Climatology》2011,106(3-4):489-497
Based on a set of very long-living (2,000?years) Qilian junipers (Sabina przewalskii Kom.) from the north-eastern part of the Tibetan Plateau (the region of Dulan), we carefully consider the regional curve standardization (RCS) technique. For this goal, we correlate deviations of individual tree-ring width records from their regional mean age-dependent curve (RC). It turns out that these correlations keep their positivity for almost all shifts between ages compared (up to 500?years and even more) evidencing each Dulan juniper to be a unique ??thermometer??. Just the unification of these ??thermometers?? in the form RC creates a spurious positive trend in the Dulan chronology. We modify the RCS technique to closer attach RC to these ??thermometers?? in order to construct a new chronology in which the trend is absent. 相似文献
849.
850.
Six sediment samples collected from the Gulf of Mexico were analyzed. Total concentrations of the PAHs ranged from 52 to 403 ng g−1 dry weight. The lowest PAH concentration without 5–6 rings PAHs appeared in S-1 sample associated with gas hydrate or gas venting. Moreover, S-1 sample had the lowest organic carbon content with 0.85% and highest reduced sulfur level with 1.21% relative to other samples. And, analysis of the sources of PAHs in S-1 sample indicated that both pyrogenic and petrogenic sources, converserly, while S-8, S-10 and S-11 sample suggested petrogenic origin. The distribution of dibenzothiophene, fluorine and dibenzofuran and the maturity parameters of triaromatic steranes suggested that organic matters in S-1 sample were different from that in S-8, S-10 and S-11 sample. This study suggested that organic geochemical data could help in distinguish the characteristic of sediment associated with gas hydrate or with oil seepage. 相似文献