D-InSAR is currently one of the most popular research tools in the field of Microwave Remote Sensing. It is unrivaled in its aspect of measuring ground deformation due to its advantages such as high resolution,continu...D-InSAR is currently one of the most popular research tools in the field of Microwave Remote Sensing. It is unrivaled in its aspect of measuring ground deformation due to its advantages such as high resolution,continuous spa-tial-coverage and dynamics. However,there are still a few major problems to be solved urgently as a result of the intrin-sic complexity of this technique. One of the problems deals with improving the accuracy of measured ground deforma-tion. In this paper,various factors affecting the accuracy of ground deformation measured by D-InSAR are systemati-cally analyzed and investigated by means of the law of measurement error propagation. At the same time,we prove that the ground deformation error not only depends on the errors of perpendicular baselines as well as the errors of the inter-ferometric phase for topographic pair and differential pair,but also on the combination of the relationship of perpen-dicular baselines for topographic pairs and differential pairs. Furthermore,a feasible approach for improving the accu-racy of measured ground deformation is proposed,which is of positive significance in the practical application of D-InSAR.展开更多
Rill formation is the predominant erosion process in slope land in the Loess Plateau, China. This study was conducted to investigate rill erosion characteristics and their effects on runoff and sediment yielding proce...Rill formation is the predominant erosion process in slope land in the Loess Plateau, China. This study was conducted to investigate rill erosion characteristics and their effects on runoff and sediment yielding processes under different slope gradients at a rate of 10°, 15°, 20° and 25° with rainfall intensity of 1.5 mm min-1 in a laboratory setting. Results revealed that mean rill depth and rill density has a positive interrelation to the slope gradient. To the contrary, width-depth ratio and distance of the longest rill to the top of the slope negatively related to slope gradient. All these suggested that increasing slope steepness could enhance rill headward erosion, vertical erosion and the fragmentation of the slope surface. Furthermore,total erosion tended to approach a stable maximum value with increasing slope, which implied that there is probably a threshold slope gradient where soil erosion begins to weaken. At the same time, the correlation analysis showed that there was a close connection between slope gradient and the variousindices of soil erosion: the correlation coefficients of slope gradient with maximal rill depth, number of rills and the distance of the longest rill from the top of the slope were 0.98, 0.97 and-0.98, respectively,indicating that slope gradient is the major factor of affecting the development of rills. Furthermore,runoff was not sensitive to slope gradient and rill formation in this study. Sediment concentration,however, is positively related to slope gradient and rill formation, the sediment concentrations increased rapidly after rill initiation, especially. These results may be essential for soil loss prediction.展开更多
A hedonic linear regression model is constructed in this paper to estimate property value, In our model, the property value （sales price） is a function of several selected variables such as the property characterist...A hedonic linear regression model is constructed in this paper to estimate property value, In our model, the property value （sales price） is a function of several selected variables such as the property characteristics, social neighborhoods, level of neighborhood environmental contaminations, level of neighborhood crimes, and locational accessibility to jobs or services, Definitions and calculation of these variables are approached by using Geographic Information System tools, For improving estimation, gravity model is employed to measure both levels of neighborhood toxic sites and crimes; and a time-based method is used to measure the loeational accessibility rather than simple straight-line distance measurement. This study discovers that the relationship between house value and its nearby highway is nonlinear, The methodology could help policy makers assess the external effects of a property. Our model also could be used potentially to identify the current and historic trends of development caused by neighborhood or environments change in the study area.展开更多
基金Projects 400471090 supported by the National Natural Science Foundation of China and 1421 by the European Space Agency
文摘D-InSAR is currently one of the most popular research tools in the field of Microwave Remote Sensing. It is unrivaled in its aspect of measuring ground deformation due to its advantages such as high resolution,continuous spa-tial-coverage and dynamics. However,there are still a few major problems to be solved urgently as a result of the intrin-sic complexity of this technique. One of the problems deals with improving the accuracy of measured ground deforma-tion. In this paper,various factors affecting the accuracy of ground deformation measured by D-InSAR are systemati-cally analyzed and investigated by means of the law of measurement error propagation. At the same time,we prove that the ground deformation error not only depends on the errors of perpendicular baselines as well as the errors of the inter-ferometric phase for topographic pair and differential pair,but also on the combination of the relationship of perpen-dicular baselines for topographic pairs and differential pairs. Furthermore,a feasible approach for improving the accu-racy of measured ground deformation is proposed,which is of positive significance in the practical application of D-InSAR.
基金Financial support for this research was provided by the National Natural Science Foundation of China (41401302)the Key Program of National Natural Science Foundation of China (41130744)+3 种基金National Natural Science Foundation of China (41271304),National Natural Science Foundation of China (41471229)Natural Science Foundation of Beijing Municipal of Education (025135303700/048)Beijing Youth Elite Project (043135336000/002)the Project of Research Base Construction of Beijing Municipal Education Commission,Key laboratory of Water Cycle and Related Land Surface Processes Foundation (201204)
文摘Rill formation is the predominant erosion process in slope land in the Loess Plateau, China. This study was conducted to investigate rill erosion characteristics and their effects on runoff and sediment yielding processes under different slope gradients at a rate of 10°, 15°, 20° and 25° with rainfall intensity of 1.5 mm min-1 in a laboratory setting. Results revealed that mean rill depth and rill density has a positive interrelation to the slope gradient. To the contrary, width-depth ratio and distance of the longest rill to the top of the slope negatively related to slope gradient. All these suggested that increasing slope steepness could enhance rill headward erosion, vertical erosion and the fragmentation of the slope surface. Furthermore,total erosion tended to approach a stable maximum value with increasing slope, which implied that there is probably a threshold slope gradient where soil erosion begins to weaken. At the same time, the correlation analysis showed that there was a close connection between slope gradient and the variousindices of soil erosion: the correlation coefficients of slope gradient with maximal rill depth, number of rills and the distance of the longest rill from the top of the slope were 0.98, 0.97 and-0.98, respectively,indicating that slope gradient is the major factor of affecting the development of rills. Furthermore,runoff was not sensitive to slope gradient and rill formation in this study. Sediment concentration,however, is positively related to slope gradient and rill formation, the sediment concentrations increased rapidly after rill initiation, especially. These results may be essential for soil loss prediction.
基金Under the auspices of the Research Client West Oakland Environmental Indicators Taskforce, Talented Foundationof Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences (No. C08Y17)
文摘A hedonic linear regression model is constructed in this paper to estimate property value, In our model, the property value （sales price） is a function of several selected variables such as the property characteristics, social neighborhoods, level of neighborhood environmental contaminations, level of neighborhood crimes, and locational accessibility to jobs or services, Definitions and calculation of these variables are approached by using Geographic Information System tools, For improving estimation, gravity model is employed to measure both levels of neighborhood toxic sites and crimes; and a time-based method is used to measure the loeational accessibility rather than simple straight-line distance measurement. This study discovers that the relationship between house value and its nearby highway is nonlinear, The methodology could help policy makers assess the external effects of a property. Our model also could be used potentially to identify the current and historic trends of development caused by neighborhood or environments change in the study area.
