基于水体透明度反演的太湖水生植被遥感信息提取   总被引：3，自引：1，他引：2  

张寿选  段洪涛  谷孝鸿 《湖泊科学》2008,20(2):184-190

在使用多光谱遥感图像提取太湖水生植被分布时,由于水体中悬浮物和藻类等物质的影响,容易产生"异物同谱"现象,大面积水体被误分为沉水植被.本文首先通过TM图像反演太湖水体的透明度,基于RVI和NDVI植被指数,分别建立两类决策树,即透明度辅助的分类决策树和无透明度参与的分类决策树,将太湖分为水体、以浮叶植被为主导的水生植被和以沉水植被为主导的水生植被等三种类型.透明度辅助下的 NDVl 分类决策树方法,较好地消除分类过程中的"异物同谱"现象,是进行太湖水生植被分类的一种最好方法选择,把这种方法应用于2002年7月15日的Landsat ETM卫星遥感影像,结果表明太湖中以沉水植被为主导的水生植被约407.6km2,以浮叶植被为主导的水生植被约82.2km2.  相似文献   

基于非均匀海水固有光学性质的透明度计算方法     

陈希  于斌  何姮君  孔凡龙  李宗叶 《海洋科学》2015,39(12):100-105

针对透明度盘只能在白天开展海水透明度测量,易受自然环境和人为因素影响、客观定量性较差的不足,提出了基于海水固有光学性质的海水透明度计算方法。该方法仿真透明度盘测量海水透明度的基本原理,采用蒙特卡罗方法,利用海水固有光学性质,计算透明度盘所处位置海水上涌光相对量,结合对比度传输方程和人眼阈值,建立了基于海水固有光学性质的海水透明度计算模型。利用2006年1月至2月共37组海水透明度的观测数据与该模型数值实验结果比较表明,测量与计算值平均绝对误差为1.1 m。利用该方法可以客观、定量、准确地计算海水透明度,并且为夜间海水透明度要素计算增加了一种新途径。  相似文献   

Long-term study of heterotrophic bacteria as indicators of eutrophication of the open middle adriatic sea     

《Estuarine, Coastal and Shelf Science》1990,30(6)

Results of the 20-year study, from 1968 to 1988, indicate a trend of increasing density of heterotrophic bacteria in the open middle Adriatic Sea. An identical trend has been observed for primary production resulting in an increase of oxygen saturation in the layer of maximum primary production. Transparency of seawater decreased during the investigated period.This suggests that fluctuations of hydrographic, chemical and biological parameters in the open middle Adriatic Sea are not only a result of the influence of natural factors but are influenced by coastal eutrophication as well. Eutrophication rapidly extended towards the open Adriatic Sea after the late 1970s.  相似文献   

Re-Envisioning the City: Lefebvre,HOPE VI,and the Neoliberalization of Urban Space     

《Urban geography》2013,34(1):114-133

This study draws upon the urban theory of Henri Lefebvre to examine HOPE VI, a public housing demolition and redevelopment program administered by the U.S. Department of Housing and Urban Development. Hailed as a new approach to urban policy, the HOPE VI program embodies many of the key tenets of neoliberal urbanization, including an emphasis on entrepreneurial forms of urban regeneration and a focus on individual responsibility. To provide a lens for understanding this neoliberalization of space, we first detail Lefebvre's theorization of abstract space and transparency, highlighting in particular its nondialectical and depoliticized character. We then turn to examine the HOPE VI model and its implementation in Charlotte, North Carolina. Lefebvre's analysis, we argue, provides a useful entry point for interpreting the re-envisioning of urban space that underlies HOPE VI-style redevelopment, and therefore can potentially inform contemporary struggles against neoliberal urban policy.  相似文献   

相干布居囚禁原子钟技术及其进展     

郭文阁  范琦  王鑫  姜海峰  张首刚 《时间频率学报》2007,30(1):45-52

分析了相干布居囚禁现象的基本原理,介绍了基于相干布居囚禁现象实现的两种原子钟实验装置的原理和结构,分析了各自的特点,并介绍了它们的研究进展以及应用前景。  相似文献   

GDI+在电子地图可视化中的应用   总被引：4，自引：1，他引：3  

车森  刘海砚  刘辉  兰梅 《测绘科学》2008,33(1):226-228

电子地图显示的美观和效率一直是设计者和用户不断追求的目标,目前电子地图的开发中普遍还是应用GDI进行图形的显示,但是GDI对电子地图显示的美观性、显示效率存在着一定的制约。GDI+作为GDI的升级版本,功能有了较大改善,针对GDI+的新特色,论文详细介绍了GDI+在电子地图可视化中的应用。实践证明,GDI+对于电子地图绘图效率的提高、显示效果的改善以及变形字体的显示,都有较好的效果。  相似文献   

基于GF-1影像的洞庭湖区水体水质遥感监测   总被引：1，自引：0，他引：1  

彭保发  陈哲夫  李建辉  罗望军  甘洁  曾荣亮 《地理研究》2018,37(9):1683-1691

湖泊水质监测是有效开展湖泊水环境综合管理与水污染防治实施的基础,也是湖泊藻华风险评估与生态安全建设的重要依据。本文基于GF-1号影像对2014-2016年洞庭湖水体的叶绿素a浓度、悬浮物浓度和透明度展开遥感监测,结果表明：叶绿素a主要集中在水流速度较慢的安乐湖、大小西湖和东洞庭湖西部地区,其他区域水体扰动力大,叶绿素含量a较低。透明度从北到南递增,与悬浮物浓度的分布趋势相反,符合常规监测规律。东洞庭湖水质较南洞庭湖和西洞庭湖差,水污染程度处于全湖最高水平。GF-1数据可精确反映叶绿素a浓度、悬浮物浓度和透明度指数的空间变化规律,也为后续高分遥感影像湖泊水质监测的应用研究提供了重要参考。  相似文献   

Seasonal and interannual variations in pigments in the Adriatic Sea     

Mira MoroviĆ 《Journal of Earth System Science》2002,111(3):215-225

Spatial and temporal variability of pigments was studied from the CZCS satellite data and fromin situ chlorophyll and transparency for the period 1979-1985. The three Adriatic sites, Northern, Middle, and Southern Adriatic are differently influenced by meteorological, hydrological and oceanographic parameters. The differences between seasonalin situ chlorophyll and remotely sensed pigment concentrations (from CZCS satellite data) from the Adriatic are large in winter. Through the correlation analysis, pigments were compared to meteo-oceanographic and hydrological parameters from different Adriatic sites. The PCA (principal component analysis) was applied to the pigment data series and significant components were compared. Different correlations are obtained for warm and cold periods of the year pointing to seasonal differences in the underlying mechanism of pigment variability. The first PC is influenced mainly by temperature. In the warm period more parameters seem to influence the pigment field, than in the cold period. The pigments in the Adriatic are in good correlation to a number of hydrologic and meteo-oceanographic factors.  相似文献   

河西地区的太阳直接辐射和大气透明度   总被引：2，自引：0，他引：2  

王尧奇  韦志刚 《气象学报》1995,53(3):375-379

利用河西地区的民勤和敦煌两个日射站的三年（１９８１—１９８３年）资料，计算了太阳直接辐射在传输过程中的各种衰减。该地区有干燥、荒漠和狭管地形等三大特点，环境对直接辐射的影响表现为气溶胶衰减的重要作用。  相似文献   

中国西部干旱地区各纬度在各种透明度状况下的可能直接辐射月辐照量     

韦志刚  王尧奇 《高原气象》1992,(2)

本文根据中国西部干旱地区太阳直接辐照度随大气质量和透明度变化的经验关系式,计算出纬度φ=28°—50°N,间隔2°,透明系数P_2=0.55—0.85,间隔0.05的可能直接辐射月辐照量。  相似文献