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1.
It is important to identify and locate glacial lakes for assessing any potential hazard. This study presents a combination of semi-automatic method Double-Window Flexible Pace Search (DFPS) and edge detection technique to identify glacial lakes using Sentinel 2A satellite data. Initially, Normalized Difference Water Index (NDWI) has been used to identify water and non-water areas, while DFPS and Edge detection technique has been used to identify an optimum threshold value to distinguish between water and shadow areas. The optimal threshold from DFPS process is 0.21, while threshold value of gradient magnitude using edge detection process is 0.318. The number of glacial lakes identified using the above algorithm is in close agreement with previously published results on glacial lakes in Gangotri glacier using different techniques. Thus, a combination of DFPS and edge detection process has successfully segregated glacial lakes from other features present in Gangotri glacier.  相似文献   
2.
摘要:土壤水分是全球水循环的重要组成成分,对研究土壤水分的空间分布、农作物长势和产量 、气候变化、水资源时空分布等有着重要意义 。本文利用Sentinel(哨兵)系列主动微波雷达卫星SAR(Sentinel-1)结合光学卫星(Sentinel-2)对格尔木中下游低矮植被覆盖下的地表土壤水分进行反演研究, 探讨不同极化组合方式和水云模型前后的土壤水分含量反演方法的适用性。结果表明:其中VV (VV Polarization) 极化对比VH (VH Polarization) 极化更加适用该区域,VV极化结合归一化水指数 (NDWI)反演地表土壤水分精度达到42.6%,拟合精度最高,VH极化仅为22.6%;利用水云模型去除植被覆盖后对地表土壤水分的反演精度有所提升,其中,VV极化精度提高约3.5%,VH极化提高1.5%;Sentinel系列卫星影像对于干旱区的土壤水分的反演具有较好的适用性。本文旨在探索一种适用于该研究区乃至柴达木盆地土壤水分实现大面积实时监测的可靠依据和手段。  相似文献   
3.
水体信息的高精度提取是水资源监测、调查与管理等研究领域的关键问题。本文选取国产GF-1卫星影像作为数据源,根据影像中典型地物光谱特征采用归一化水体指数法(NDWI)、多波段谱间关系法对研究区进行了水体提取,并通过结果分析提出了基于主成分分析与多尺度分割技术的综合水体信息提取方法。对以上4种方法进行对比分析,验证结果表明:归一化水体指数法易受阴影信息影响;改进的多波段谱间关系法能较为完整地提取水体信息,但受小范围阴影信息影响;主成分分析综合法总体精度较高;多尺度分割提取法能有效地分离水体信息与非水体信息,水体信息提取的效果最佳。  相似文献   
4.
以山东省为研究区域,利用2009年9月MODIS的8 d合成波段反射率产品MOD09,选择特征变量植被指数(NDVI、EVI)、NDWI、NDMI、NDSI及辅助信息DEM,通过选取其中的影像特征组合来确定分类方案,构建各波段组合的CART决策树,对MODIS影像进行分类,得到CART决策树的最优波段组合。结果表明,特征变量DEM、NDVI、EVI对分类结果贡献较大;将CART决策树的分类结果与其相对应的最大似然分类结果进行比较可知,基于影像多特征的CART决策树分类方法能明显提高分类精度。  相似文献   
5.
Multi-temporal series of satellite SPOT-VEGETATION normalized difference vegetation index (NDVI) and normalized difference water index (NDWI) data from 1998 to 2007 were used for analyzing vegetation change of the ecotone in the west of the Northeast China Plain. The yearly and monthly maximal values,anomalies and change rates of NDVI and NDWI were calculated to reveal the interannual and seasonal changes in vegetation cover and vegetation water content. Linear regression method was adopted to characterize the trends in vegetation change. The yearly maximal NDVI decreased from 0.41 in 1998 to 0.37 in 2007,implying the decreasing trend of vegetation activity. There was a significant decrease of maximal NDVI in spring and summer over the study period,while an increase trend was observed in autumn. The vegetation-improved regions and vegetation-degraded regions occupied 17.03% and 20.30% of the study area,respectively. The maximal NDWI over growing season dropped by 0.027 in 1998–2007,and about 15.15% of the study area showed a decreasing trend of water content. Vegetation water stress in autumn was better than that in spring. Vegetation cover and water content variations were sensitive to annual precipitation,autumn precipitation and summer temperature. The vegetation degradation trend in this ecotone might be induced by the warm-drying climate especially continuous spring and summer drought in the recent ten years.  相似文献   
6.
光合有效辐射分量(Fraction of Photosynthetically Active Radiation,FPAR)是进行生态系统功能和全球变化研究的重要参数,准确估算FPAR具有重要意义。通过对野外实测玉米高光谱数据和光合有效辐射数据的分析,探讨了主成分分析方法在高光谱信息提取及估算玉米冠层FPAR参数方面的可行性,在此基础上,结合植被指数验证FPAR估算效果,分析近红外及短波红外高光谱数据在FPAR估算方面的应用潜力。  相似文献   
7.
鉴于采用传统方法在提取高分辨率影像水域信息存在不足,本文以高分辨率国产卫星高分一号宽幅16 m空间分辨率多光谱影像为数据源,以浙江省钱塘江流域为研究区域,通过预先对影像进行NDWI处理,在此基础上利用改进FCM聚类算法实现了水域信息的自动提取,并与传统的NDWI和ISODATA分类方法提取结果进行比较。结果表明,该方法在分类效果和精度方面均优于传统分类方法,作为国产高分一号影像水域信息自动提取方法是可行的。  相似文献   
8.
环境一号卫星系统是专门用于环境和灾害监测的,对地观测系统由两颗光学卫星HJ-1A和HJ-1B组成,拥有光学、红外、超光谱多种探测手段,具有大范围、全天候、动态的环境和灾害监测能力。本文以南京的环境一号卫星影像为例,运用归一化差异水体指数法提取并分析了南京市市区湖泊分布信息,得到了较为满意的结果。  相似文献   
9.
利用伪归一化差异水体指数提取城镇周边   总被引:1,自引:0,他引:1  
通过对归一化差异水体指数NDWI中的绿波段修正,提出了不依赖于中红外波段的伪归一化差异水体指数FNDWI(False NDWI)。使用NDWI和FNDWI分别在背景地物为城市、城郊、乡镇、村落和山区的遥感影像上进行河流水体提取,实验表明,FNDWI影像中城镇建筑用地与河流水体的可分离性较NDWI有所提升,提升率为116%~335%不等;相关性分析表明,河流宽度与可分离性提升率具有明显的负相关关系,相关系数为-0.82;分类结果显示,在城市和城郊区域,NDWI提取的水体中混杂有较多城镇建筑用地信息,而FNDWI提取的水体中基本未见混杂。总体上,FNDWI提高了2种地物的可分离性,剔除了NDWI影像混入的城镇建筑用地信息,较好地解决了NDWI城镇建筑用地与河流水体的混淆问题,尤其适用于城镇周边的细小河流。  相似文献   
10.
Our study examines the relationships among various environmental variables in Surat city using remote sensing. Landsat Thematic Mapper satellite data were used in conjugation with geospatial techniques to study urbanization and correlation among satellite-derived biophysical parameters namely, normalized difference vegetation index (NDVI), normalized difference built-up index (NDBI), normalized difference water index (NDWI), normalized difference bareness index (NDBaI) and land surface temperature (LST). A modified NDWI (MNDWI) was used for extracting areas under water. Land use/land cover classification was performed using hierarchical decision tree classification technique using ERDAS IMAGINE Expert classifier with an accuracy of 90.4% for 1990 and 85% for 2009. It was found that city has expanded over 42.75 sq.km within two decades. Built-up, fallow and sediment land use classes exhibited high dynamics with increase of nearly 200% and 50% and decrease of 55% respectively from 1990 to 2009. Vegetation and water classes were less dynamic with 20% decrease and 15% increase. The transformation of land parcels from vegetation to built-up, vegetation to fallow and fallow to built-up has resulted in increase of LST by 5.5 ± 2.6°C, 6.7 ± 3°C and 3.5 ± 2.9°C, respectively.  相似文献   
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