Chongqing, China
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Deng F.,Wuhan University | Li P.,Wuhan University | Li P.,Chongqing Geomatics Center | Kan Y.,The Land Remediation Bureau of Hubei Province | And 2 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2017

To solve the problem of large-scale urban true orthophoto generation, the paper proposes an occlusion detection based on the overall projection of digital building models (DBMs). Using the surface of DBM storage with triangular facets and raster inside projection of plane graphics do not shelter, weuse triangular face as a unit to orthographic projection of the entire buildings to get polygon of the roof. Make perspective projection of the entire buildings to get the polygon of the building on the image, then get the polygon of the whole building on traditional orthophoto based on DEM projection iteration. We can get the occlusion areas of the building by subtracting two polygons. Finally, we get the true orthophoto after repairing the occlusion areas with the best image. The experiment shows that the method can detect the occlusion areas quickly and accurately and provide a prediction to generate high-quality true orthophoto. © 2017, Research and Development Office of Wuhan University. All right reserved.

Chai L.,Beijing Normal University | Wu F.,Beijing Normal University | Wu F.,Chongqing Geomatics Center | Zhang L.,Beijing Normal University | Shi J.,CAS Institute of Remote Sensing
Journal of Remote Sensing | Year: 2015

We proposed a method to estimate single scattering albedo of winter wheat over the North China Plain with AMSR-E passive microwave imagery. The relationships of single scattering albedo and optical depth between 6.925 GHz and 10.65 GHz were derived from simulations. To retrieve the single scattering albedo, the relationships were combined with the physical expressions of microwave vegetation indices derived from the first-order parameterized emission model. Comparisons with normalized difference vegetation index (NDVI) obtained from daily MODIS reflectance product showed that the variations in winter wheat single scattering albedo were similar to those of winter wheat NDVI. However, several differences were observed. NDVI showed saturation from the heading stage to the milky stage of winter wheat, whereas single scattering albedo remained sensitive to the growth of winter wheat. Single scattering albedo offers certain advantages in reflecting the growth status of winter wheat. ©, 2015, Editorial Board of Chinese Journal of Applied Ecology. All right reserved.

Xu Y.,China Agricultural University | Luo D.,Chongqing Geomatics Center | Peng J.,Central University of Costa Rica
Journal of Geographical Sciences | Year: 2011

Due to the extremely poor soil cover, a low soil-forming rate, and inappropriate intensive land use, soil erosion is a serious problem in Guizhou Province, which is located in the centre of the karst areas of Southwest China. In order to bring soil erosion under control and restore environment, the Chinese Government has initiated a serious of ecological rehabilitation projects such as the Grain-for-Green Programme and Natural Forest Protection Program and brought about tremendous influences on land-use change and soil erosion in Guizhou Province. This paper explored the relationship between land use and soil erosion in the Maotiao River watershed, a typical agricultural area with severe soil erosion in central Guizhou Province. In this study, we analyzed the spatio-temporal dynamic change of land-use type in Maotiao River watershed from 1973 to 2007 using Landsat MSS image in 1973, Landsat TM data in 1990 and 2007. Soil erosion change characteristics from 1973 to 2007, and soil loss among different land-use types were examined by integrating the Revised Universal Soil Loss Equation (RUSLE) with a GIS environment. The results indicate that changes in land use within the watershed have significantly affected soil erosion. From 1973 to 1990, dry farmland and rocky desertified land significantly increased. In contrast, shrubby land, other forestland and grassland significantly decreased, which caused accelerated soil erosion in the study area. This trend was reversed from 1990 to 2007 with an increased area of land-use types for ecological use owing to the implementation of environmental protection programs. Soil erosion also significantly varied among land-use types. Erosion was most serious in dry farmland and the lightest in paddy field. Dry farmland with a gradient of 6°-25° was the major contributor to soil erosion, and conservation practices should be taken in these areas. The results of this study provide useful information for decision makers and planners to take sustainable land use management and soil conservation measures in the area. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg.

Zhang Q.,China Agricultural University | Xiao H.,China Agricultural University | Xiao H.,Chongqing Geomatics Center | Duan M.,China Agricultural University | And 2 more authors.
Land Use Policy | Year: 2015

Agricultural infrastructure construction is an important component of agricultural policies in China that aim to increase production and ensure food security. One objective of agricultural infrastructure is to promote modern intensive agriculture, which has already caused agri-environmental problems including environmental pollution, landscape degradation, and biodiversity loss. In European countries, agri-environmental measures are widely implemented with farmers' participation, and it is anticipated that these measures will be introduce into agricultural policies, such as agricultural infrastructure projects, in China. As one of the direct stakeholders, farmers and their attitudes towards agricultural infrastructure projects and their perceptions of agri-environmental issues need to be understood before the policy is implemented. This research aimed to determine farmers' attitudes towards agricultural infrastructure projects and the possible incorporation of agri-environmental measures in these projects using a questionnaire survey in Beijing and Changsha. The results showed that farmers were generally unsatisfied with the top-down implementation process of agricultural infrastructure projects because they were seldom involved and felt their needs were not considered by the authorities. Most farmers would accept at least one simple agri-environmental measure, and subsidies could significantly increase the acceptance level. Economic risk and farm business type were crucial factors influencing farmers' acceptance of measures. We suggested that if governments hope to implement agri-environmental measures as part of agricultural infrastructure projects, improving the public participation process should be a priority, and a combination of top-down and bottom-up approaches should be considered with respect to farmers' knowledge, opinions and farm business types to design suitable measures for local conditions. © 2015 Elsevier Ltd.

Wu H.,Chongqing Geomatics Center | Yao Y.,Wuhan University | Chen P.,Xi'an University of Science and Technology | Xiao Y.,Chongqing Geomatics Center
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2013

As an important part in the near-Earth space environment, the ionosphere activity is closely related to human survival and development and has a significant impact for production and life of human beings. At present, most studies are based on the ionosphere ionospheric total electron content (TEC). It can only reflect the level of the ionosphere structure, but cannot reflect the vertical structure of the ionosphere. Computerized ionospheric tomography (CIT) technology based on GNSS is most convenient and effective. Analyzing CIT techniques, some conditions are proposed to prove its accuracy and reliability. Using observation data provided by IGS stations on August 3, 2010, an ionospheric image of the European region is reconstructed. It shows the feasibility of this method.

Lin N.,Chongqing Jiaotong University | Lin N.,Chengdu University of Technology | Yang W.,Chengdu University of Technology | Wang B.,Chongqing Geomatics Center
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2013

Hyperspectral image linear feature extraction methods often cause information loss and distortion. In view of this, a new kernel minimum noise fraction (KMNF) transform hyperspectral image nonlinear feature extraction method is proposed that introduces a kernel method to minimum noise fraction (MNF) transform. Hyperspectral image KMNF feature extraction experiments were carried out. CUPRITE AVIRIS data experimental results show that sample number influences KMNF slightly, a small number of samples can get almost the same result as a large number of samples; KMNF feature extraction reflects the nonlinear characteristics of hyperspectral images, and endmember extraction effects based on KMNF images outweigh MNF images.

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