Massive volumes of global geospatial information are being collected by newly designed acquisition devices and generated by various geospatial applications.This poses a critical challenge to efficiently organize and e...Massive volumes of global geospatial information are being collected by newly designed acquisition devices and generated by various geospatial applications.This poses a critical challenge to efficiently organize and effectively integrate global multi-source geospatial information.This paper introduces a global seamless data model for the organization of huge multi-source,multi-resolution and multi-temporal geospatial data.Based on this data model,the management of the global multi-resolution pyramid is discussed in detail.To integrate geospatial data and processing functions from various GIS systems,a service-oriented framework is presented through the technology of Virtual Globe.Finally,a Virtual Globe system,GeoGlobe,is developed and illustrated.展开更多
Resolution has been playing a significant role in landslide susceptibility mapping and hazard assessment.Based on geographical information system(GIS) and information model,the effects of raster resolution on landslid...Resolution has been playing a significant role in landslide susceptibility mapping and hazard assessment.Based on geographical information system(GIS) and information model,the effects of raster resolution on landslide susceptibility mapping are studied in a central area of Shenzhen,China.Eight factors are selected to calculate landslide susceptibility with eleven groups of different resolutions(5 to 190 m).It has been found that a finer resolution does not necessarily lead to a higher accuracy of landslide susceptibility mappings,while the result of 90 m-resolution has the best accuracy and the 150 m-resolution has the worst one.The accuracy curve is in a shape of "W" along with resolution decreasing:1) The accuracy decreases from 5 to 70 m;2) and then the best accuracy appears at 90 m,which is almost the same as the mean size of landslides in study area;3) the accuracy decreases again from 110 to 150 m;4) and finally the accuracy increases from 150 to 190 m.The sensitivity analysis indicates that the effects of raster resolution are mainly caused by the resolution impact on landform parameter derivation,while factors like geology and human activity are very insensitive to resolutions.A further study shows that in flat,ridge,and slope foot terrains,the susceptibility mapping result is sensitive to resolution,but in the sloping surface area the sensitivity is much less sensitive to resolution.At last,by choosing study areas with different sizes,it has also been found that the optimal resolutions are variable due to size of study area.But the study area is larger than a threshold,which is 135 km2 in this study,and the optimal resolution is almost fixed.展开更多
Inverse synthetic aperture radar (ISAR) image can be represented and reconstructed by sparse recovery (SR) approaches. However, the existing SR algorithms, which are used for ISAR imaging, have suffered from high comp...Inverse synthetic aperture radar (ISAR) image can be represented and reconstructed by sparse recovery (SR) approaches. However, the existing SR algorithms, which are used for ISAR imaging, have suffered from high computational cost and poor imaging quality under a low signal to noise ratio (SNR) condition. This paper proposes a fast decoupled ISAR imaging method by exploiting the inherent structural sparse information of the targets. Firstly, the ISAR imaging problem is decoupled into two sub-problems. One is range direction imaging and the other is azimuth direction focusing. Secondly, an efficient two-stage SR method is proposed to obtain higher resolution range profiles by using jointly sparse information. Finally, the residual linear Bregman iteration via fast Fourier transforms (RLBI-FFT) is proposed to perform the azimuth focusing on low SNR efficiently. Theoretical analysis and simulation results show that the proposed method has better performence to efficiently implement higher-resolution ISAR imaging under the low SNR condition.展开更多
基金supported by the Natural Science Foundation of China (Grant No.40801163)the Innovation Research Group of NSFC (Grant No.40721001)the National Basic Research Program of China ("973" Program)(Grant No.2006CB701304)
文摘Massive volumes of global geospatial information are being collected by newly designed acquisition devices and generated by various geospatial applications.This poses a critical challenge to efficiently organize and effectively integrate global multi-source geospatial information.This paper introduces a global seamless data model for the organization of huge multi-source,multi-resolution and multi-temporal geospatial data.Based on this data model,the management of the global multi-resolution pyramid is discussed in detail.To integrate geospatial data and processing functions from various GIS systems,a service-oriented framework is presented through the technology of Virtual Globe.Finally,a Virtual Globe system,GeoGlobe,is developed and illustrated.
基金Supported by the National Hi-Tech Research and development Program of China ("863")(Grant No. 2007AA120502)the National Natural Science Foundation of China (Grant No. 40629001)
文摘Resolution has been playing a significant role in landslide susceptibility mapping and hazard assessment.Based on geographical information system(GIS) and information model,the effects of raster resolution on landslide susceptibility mapping are studied in a central area of Shenzhen,China.Eight factors are selected to calculate landslide susceptibility with eleven groups of different resolutions(5 to 190 m).It has been found that a finer resolution does not necessarily lead to a higher accuracy of landslide susceptibility mappings,while the result of 90 m-resolution has the best accuracy and the 150 m-resolution has the worst one.The accuracy curve is in a shape of "W" along with resolution decreasing:1) The accuracy decreases from 5 to 70 m;2) and then the best accuracy appears at 90 m,which is almost the same as the mean size of landslides in study area;3) the accuracy decreases again from 110 to 150 m;4) and finally the accuracy increases from 150 to 190 m.The sensitivity analysis indicates that the effects of raster resolution are mainly caused by the resolution impact on landform parameter derivation,while factors like geology and human activity are very insensitive to resolutions.A further study shows that in flat,ridge,and slope foot terrains,the susceptibility mapping result is sensitive to resolution,but in the sloping surface area the sensitivity is much less sensitive to resolution.At last,by choosing study areas with different sizes,it has also been found that the optimal resolutions are variable due to size of study area.But the study area is larger than a threshold,which is 135 km2 in this study,and the optimal resolution is almost fixed.
基金supported by the National Natural Science Foundation of China(61671469)
文摘Inverse synthetic aperture radar (ISAR) image can be represented and reconstructed by sparse recovery (SR) approaches. However, the existing SR algorithms, which are used for ISAR imaging, have suffered from high computational cost and poor imaging quality under a low signal to noise ratio (SNR) condition. This paper proposes a fast decoupled ISAR imaging method by exploiting the inherent structural sparse information of the targets. Firstly, the ISAR imaging problem is decoupled into two sub-problems. One is range direction imaging and the other is azimuth direction focusing. Secondly, an efficient two-stage SR method is proposed to obtain higher resolution range profiles by using jointly sparse information. Finally, the residual linear Bregman iteration via fast Fourier transforms (RLBI-FFT) is proposed to perform the azimuth focusing on low SNR efficiently. Theoretical analysis and simulation results show that the proposed method has better performence to efficiently implement higher-resolution ISAR imaging under the low SNR condition.
