准确、快速、低成本的获取高潜水位煤矿区沉陷耕地的面积、分布、受损等信息对耕地保护有重要的意义。色彩空间转换、纹理分析和植被指数等方法能够有效的增强和挖掘影像潜在的信息,对信息提取有很大帮助。利用2018年4月获取的无人机可...准确、快速、低成本的获取高潜水位煤矿区沉陷耕地的面积、分布、受损等信息对耕地保护有重要的意义。色彩空间转换、纹理分析和植被指数等方法能够有效的增强和挖掘影像潜在的信息,对信息提取有很大帮助。利用2018年4月获取的无人机可见光影像对典型高潜水位煤矿区--山东兖州兴隆庄煤矿的沉陷耕地进行了提取研究。首先统计了耕地、积水区等地物在可见光三波段的均值和标准差,比较发现耕地与积水区在红、绿、蓝3个波段均有重合。其次对研究区影像进行了色彩空间转换与二阶矩阵纹理滤波,统计了耕地与积水区共27项色彩与纹理特征指标,利用均值和标准差计算了变异系数和相对差异值,最终选取色度(变异系数26%,相对差异73.33%)和绿色信息熵(变异系数20.59%,相对差异72.79%)作为耕地提取的最优特征,采用最大似然法进行耕地提取。之后计算了备选的6种可见光植被指数,根据结果分布图,选取了过绿指数EXG(excess green index)、可见光差异植被指数VDVI(visible-band difference vegetation index)、红绿蓝植被指数RGBVI(red green blue vegetation index)及归一化绿红差异指数NGRDI(normalized green-red difference index)作为沉陷耕地提取指数,利用双峰阈值法确定了耕地提取阈值。比较提取结果得出,EXG和NGRDI指数无法全面、客观反映研究区实际情况,VDVI指数的耕地总体分类精度为81.05%,高于RGBVI指数的71.38%,是本研究中最适用于高潜水位煤矿区沉陷耕地提取的指数。最后利用验证区影像,以基于样本面向对象提取的沉陷耕地面积作为参考值,通过比较面积及误差得出,基于色彩与纹理特征法提取的面积与参考面积更接近,误差(6.8%)小于可见光植被指数法(16.0%),更适用于高潜水位煤矿区沉陷耕地的提取。本研究结果客观反映了由于采煤沉陷导致耕地颜色、纹理、疏密等变化特征,为�展开更多
The Nile Delta is considered to be one of the most vulnerable river deltas to Sea Level Rise (SLR) in the world. SLR is expected to affect large agricultural areas of the Nile Delta, either through inundation or highe...The Nile Delta is considered to be one of the most vulnerable river deltas to Sea Level Rise (SLR) in the world. SLR is expected to affect large agricultural areas of the Nile Delta, either through inundation or higher levels and salinity of groundwater. It could be argued that such impacts would augment the problems experienced already in the area in terms of high groundwater table and salinity levels. In order to guide policy and decision making, especially in terms of assessing the economics of various adaptation options, there is a need to provide estimates of potential economic damage that could result from such changes. The paper in hand aims to estimate the economic value of potential primary impacts of higher levels of groundwater table due to expected SLR on agriculture productivity in Damietta Governorate as one of the Nile Delta coastal governorates. To conduct such an assessment, relationship between groundwater table level and agricultural productivity was first investigated in relevant literature. This was followed by reviewing prevailing conditions in the agricultural sector in the study area. Thereafter, a regression analysis for the main crops in the study area, between crop yield and groundwater table levels, was conducted. Based on the developed regression, a GIS (Geographic Information System)-based hydrological model, and a production economic model, were employed to assess economic value of higher levels of groundwater table impacts on agriculture productivity. It was found that future accumulative crop yield loss was estimated, using segmented linear regression, up to the year 2100 to be as much as L.E. 6.43 billion. It is worth mentioning that these estimates do not include indirect impacts of higher levels of groundwater table, which may include loss of jobs and/or earnings, impacts on food supply and food security in the area. A potential adaptation option, namely redesigning and upgrading existing drainage infrastructure, was found to cost a total of L.E. 190.8 million, representing abo展开更多
文摘准确、快速、低成本的获取高潜水位煤矿区沉陷耕地的面积、分布、受损等信息对耕地保护有重要的意义。色彩空间转换、纹理分析和植被指数等方法能够有效的增强和挖掘影像潜在的信息,对信息提取有很大帮助。利用2018年4月获取的无人机可见光影像对典型高潜水位煤矿区--山东兖州兴隆庄煤矿的沉陷耕地进行了提取研究。首先统计了耕地、积水区等地物在可见光三波段的均值和标准差,比较发现耕地与积水区在红、绿、蓝3个波段均有重合。其次对研究区影像进行了色彩空间转换与二阶矩阵纹理滤波,统计了耕地与积水区共27项色彩与纹理特征指标,利用均值和标准差计算了变异系数和相对差异值,最终选取色度(变异系数26%,相对差异73.33%)和绿色信息熵(变异系数20.59%,相对差异72.79%)作为耕地提取的最优特征,采用最大似然法进行耕地提取。之后计算了备选的6种可见光植被指数,根据结果分布图,选取了过绿指数EXG(excess green index)、可见光差异植被指数VDVI(visible-band difference vegetation index)、红绿蓝植被指数RGBVI(red green blue vegetation index)及归一化绿红差异指数NGRDI(normalized green-red difference index)作为沉陷耕地提取指数,利用双峰阈值法确定了耕地提取阈值。比较提取结果得出,EXG和NGRDI指数无法全面、客观反映研究区实际情况,VDVI指数的耕地总体分类精度为81.05%,高于RGBVI指数的71.38%,是本研究中最适用于高潜水位煤矿区沉陷耕地提取的指数。最后利用验证区影像,以基于样本面向对象提取的沉陷耕地面积作为参考值,通过比较面积及误差得出,基于色彩与纹理特征法提取的面积与参考面积更接近,误差(6.8%)小于可见光植被指数法(16.0%),更适用于高潜水位煤矿区沉陷耕地的提取。本研究结果客观反映了由于采煤沉陷导致耕地颜色、纹理、疏密等变化特征,为�
文摘The Nile Delta is considered to be one of the most vulnerable river deltas to Sea Level Rise (SLR) in the world. SLR is expected to affect large agricultural areas of the Nile Delta, either through inundation or higher levels and salinity of groundwater. It could be argued that such impacts would augment the problems experienced already in the area in terms of high groundwater table and salinity levels. In order to guide policy and decision making, especially in terms of assessing the economics of various adaptation options, there is a need to provide estimates of potential economic damage that could result from such changes. The paper in hand aims to estimate the economic value of potential primary impacts of higher levels of groundwater table due to expected SLR on agriculture productivity in Damietta Governorate as one of the Nile Delta coastal governorates. To conduct such an assessment, relationship between groundwater table level and agricultural productivity was first investigated in relevant literature. This was followed by reviewing prevailing conditions in the agricultural sector in the study area. Thereafter, a regression analysis for the main crops in the study area, between crop yield and groundwater table levels, was conducted. Based on the developed regression, a GIS (Geographic Information System)-based hydrological model, and a production economic model, were employed to assess economic value of higher levels of groundwater table impacts on agriculture productivity. It was found that future accumulative crop yield loss was estimated, using segmented linear regression, up to the year 2100 to be as much as L.E. 6.43 billion. It is worth mentioning that these estimates do not include indirect impacts of higher levels of groundwater table, which may include loss of jobs and/or earnings, impacts on food supply and food security in the area. A potential adaptation option, namely redesigning and upgrading existing drainage infrastructure, was found to cost a total of L.E. 190.8 million, representing abo
文摘对塔里木河下游断流河道2000～2002年9个地下水监测断面和18个植被样地的实地监测资料分析表明,地下水埋深对天然植被的组成、分布及长势有直接关系.地下水位的不断下降和土壤含水率大大丧失是引起塔里木河下游植被退化的主导因子.塔里木河下游的四次输水对其下游地下水位抬升起到了积极作用,河道附近地下水位呈逐级抬升过程,横向影响范围达1000 m左右,纵向上,表现为上段地下水抬升幅度较大(达84%),下段抬升幅度较小(6%).随着地下水位的抬升,天然植被的响应范围由第一次输水后的200～250 m,扩展到第四次输水的800 m.
