The problems of the earth's gravity fields' visualization are both focus and puzzle currently. Aiming at multiresolution rendering, modeling of the Earth's gravity fields' data is discussed in the pape...The problems of the earth's gravity fields' visualization are both focus and puzzle currently. Aiming at multiresolution rendering, modeling of the Earth's gravity fields' data is discussed in the paper by using LOD algorithm based on Quad Tree. First, this paper employed the method of LOD based on Quad Tree to divide up the regional gravity anomaly data, introduced the combined node evaluation system that was composed of viewpoint related and roughness related systems, and then eliminated the T-cracks that appeared among the gravity anomaly data grids with different resolutions. The test results demonstrated that the gravity anomaly data grids' rendering effects were living, and the computational power was low. Therefore, the proposed algorithm was a suitable method for modeling the gravity anomaly data and has potential applications in visualization of the earth's gravity fields.展开更多
The acquisition of precise soil data representative of the entire survey area, is a critical issue for many treatments such as irrigation or fertilization in precision agriculture. The aim of this study was to investi...The acquisition of precise soil data representative of the entire survey area, is a critical issue for many treatments such as irrigation or fertilization in precision agriculture. The aim of this study was to investigate the spatial variability of soil bulk electrical conductivity （ECb） in a coastal saline field and design an optimized spatial sampling scheme of ECb based on a sampling design algorithm, the variance quad-tree （VQT） method. Soil ECb data were collected from the field at 20 m interval in a regular grid scheme. The smooth contour map of the whole field was obtained by ordinary kriging interpolation, VQT algorithm was then used to split the smooth contour map into strata of different number desired, the sampling locations can be selected within each stratum in subsequent sampling. The result indicated that the probability of choosing representative sampling sites was increased significantly by using VQT method with the sampling number being greatly reduced compared to grid sampling design while retaining the same prediction accuracy. The advantage of the VQT method is that this scheme samples sparsely in fields where the spatial variability is relatively uniform and more intensive where the variability is large. Thus the sampling efficiency can be improved, hence facilitate an assessment methodology that can be applied in a rapid, practical and cost-effective manner.展开更多
针对序贯式融合方法常常会降低多波段图像间原有差异的问题,提出了基于嵌入式多尺度变换(embedded multi-scale transform,EMT)和局部差异特征的多波段图像融合方法.利用支持度变换法(support value transform,SVT)分别分解多波段图像;...针对序贯式融合方法常常会降低多波段图像间原有差异的问题,提出了基于嵌入式多尺度变换(embedded multi-scale transform,EMT)和局部差异特征的多波段图像融合方法.利用支持度变换法(support value transform,SVT)分别分解多波段图像;再采用四叉树(quad-tree,QT)法分解灰度值较分散的某波段图像的最后一层低频成分图像,以分解得到的块图像为标准分别分割其他波段的最后一层低频成分图像;采用可能性理论的析取融合规则对多波段低频块图像进行特征级融合;遍历所有块得到低频融合图像块;将拼接得到的低频融合图像与像素级逐层融合得到的支持度图像序列进行逆变换,获得最终融合图像.实验结果表明:四叉树分解融合有显著效果,与单纯的四叉树融合相比,嵌入式多尺度分解融合图像的边缘强度提高了13.31%,对比度提升了2.63%,熵提高了4.26%,运行时间下降了87.11%,证明了所提出方法的有效性.展开更多
文摘The problems of the earth's gravity fields' visualization are both focus and puzzle currently. Aiming at multiresolution rendering, modeling of the Earth's gravity fields' data is discussed in the paper by using LOD algorithm based on Quad Tree. First, this paper employed the method of LOD based on Quad Tree to divide up the regional gravity anomaly data, introduced the combined node evaluation system that was composed of viewpoint related and roughness related systems, and then eliminated the T-cracks that appeared among the gravity anomaly data grids with different resolutions. The test results demonstrated that the gravity anomaly data grids' rendering effects were living, and the computational power was low. Therefore, the proposed algorithm was a suitable method for modeling the gravity anomaly data and has potential applications in visualization of the earth's gravity fields.
基金We thank the financial support from the National Natural Science Foundation of China(40701007,40571066)the Postdoctoral Science Foundation of China(20060401048).
文摘The acquisition of precise soil data representative of the entire survey area, is a critical issue for many treatments such as irrigation or fertilization in precision agriculture. The aim of this study was to investigate the spatial variability of soil bulk electrical conductivity （ECb） in a coastal saline field and design an optimized spatial sampling scheme of ECb based on a sampling design algorithm, the variance quad-tree （VQT） method. Soil ECb data were collected from the field at 20 m interval in a regular grid scheme. The smooth contour map of the whole field was obtained by ordinary kriging interpolation, VQT algorithm was then used to split the smooth contour map into strata of different number desired, the sampling locations can be selected within each stratum in subsequent sampling. The result indicated that the probability of choosing representative sampling sites was increased significantly by using VQT method with the sampling number being greatly reduced compared to grid sampling design while retaining the same prediction accuracy. The advantage of the VQT method is that this scheme samples sparsely in fields where the spatial variability is relatively uniform and more intensive where the variability is large. Thus the sampling efficiency can be improved, hence facilitate an assessment methodology that can be applied in a rapid, practical and cost-effective manner.
文摘针对序贯式融合方法常常会降低多波段图像间原有差异的问题,提出了基于嵌入式多尺度变换(embedded multi-scale transform,EMT)和局部差异特征的多波段图像融合方法.利用支持度变换法(support value transform,SVT)分别分解多波段图像;再采用四叉树(quad-tree,QT)法分解灰度值较分散的某波段图像的最后一层低频成分图像,以分解得到的块图像为标准分别分割其他波段的最后一层低频成分图像;采用可能性理论的析取融合规则对多波段低频块图像进行特征级融合;遍历所有块得到低频融合图像块;将拼接得到的低频融合图像与像素级逐层融合得到的支持度图像序列进行逆变换,获得最终融合图像.实验结果表明:四叉树分解融合有显著效果,与单纯的四叉树融合相比,嵌入式多尺度分解融合图像的边缘强度提高了13.31%,对比度提升了2.63%,熵提高了4.26%,运行时间下降了87.11%,证明了所提出方法的有效性.
