The geosynchronous circular synthetic aperture radar (GEOCSAR) is an innovative SAR system,which can produce high resolution three-dimensional (3D) images and has the potential to provide 3D deformation measurement.Wi...The geosynchronous circular synthetic aperture radar (GEOCSAR) is an innovative SAR system,which can produce high resolution three-dimensional (3D) images and has the potential to provide 3D deformation measurement.With an orbit altitude of approximately 36 000 km,the orbit motion and orbit disturbance effects of GEOCSAR behave differently from those of the conventional spaceborne SAR.In this paper,we analyze the effects of orbit errors on GEOCSAR imaging and interferometric processing.First,we present the GEOCSAR imaging geometry and the orbit errors model based on perturbation analysis.Then,we give the GEOCSAR signal formulation based on imaging geometry,and analyze the effect of the orbit error on the output focused signal.By interferometric processing on the 3D reconstructed images,the relationship between satellite orbit errors and the interferometric phase is deduced.Simulations demonstrate the effects of orbit errors on the GEOCSAR images,interferograms,and the deformations.The conclusions are that the required relative accuracy of orbit estimation should be at centimeter level for GEOCSAR imaging at L-band,and that millimeter-scale accuracy is needed for GEOCSAR interferometric processing.展开更多
野外地质实践教学是高校地质类教学的重要组成部分,而教学安全是野外实践教学顺利进行的必要前提。为对教学路线进行全面、准确的风险评价,首先提出了针对山区野外地质实践教学实习路线的安全风险评价指标体系,其涵盖了滑坡风险、崩塌...野外地质实践教学是高校地质类教学的重要组成部分,而教学安全是野外实践教学顺利进行的必要前提。为对教学路线进行全面、准确的风险评价,首先提出了针对山区野外地质实践教学实习路线的安全风险评价指标体系,其涵盖了滑坡风险、崩塌风险和滑倒风险3类常见风险;然后通过使用基于层次分析(analytic hierarchy process,AHP)法和合成孔径雷达差分干涉测量(differential interferometric synthetic aperture radar,D-InSAR)的滑坡风险量化模型进行滑坡风险评价,使用结合危岩判别的易发处数量-运动距离耦合评价模型进行崩塌风险评价,使用组合权重的优劣解距离法(technique for order preference by similarity to an ideal solution,TOPSIS)进行滑倒风险评价,并使用组合权重的优劣解距离法得到3类风险的综合评价结果,构建了山区野外地质实践教学实习路线安全风险综合评价方法;最后将该方法应用于链子崖实习路线。结果表明:链子崖实习路线风险值整体较低,处于“较安全”水平,但局部存在“较不安全”路段,需要特别关注。研究提出的评价方法具有可行性与合理性,可以为保障实习人员的安全提供科学参考,并为野外地质实践教学安全与风险综合评价方法提供借鉴。展开更多
The Square Kilometre Array(SKA)has the potential to revolutionize astronomical research through its unparalleled precision.A critical aspect of SKA imaging is the computation of the UVW coordinates,which must be accur...The Square Kilometre Array(SKA)has the potential to revolutionize astronomical research through its unparalleled precision.A critical aspect of SKA imaging is the computation of the UVW coordinates,which must be accurate and reliable for the development of the SKA scientific data processor.Katpoint is the current method used to calculate UVW in Meer KAT.Using a pseudo-source,we employ a simple cross-product method to determine UVWs.In this study,we explore the applicability of Katpoint for SKA1-low and SKA1-mid and evaluate its precision.The conventional method,CALC/Omni UV,and Katpoint were quantitatively assessed through simulations.The results indicate that Katpoint exhibits substantial accuracy with MeerKAT compared to traditional techniques.However,its precision is slightly inadequate for the long baselines of SKA1.We improved the precision of Katpoint by identifying optimal offset values for pseudo-sources on the SKA1 telescope through simulation,finding a 0°.11 offset suitable for SKA1-Mid and a 0°.045 offset for SKA1-Low.Final result validations demonstrate that these adjustments render the computational accuracy fully comparable to the standard CALC/Omni UV method,which would meet the requirements of SKA high-precision imaging and offer a solution for high-precision imaging in radio interferometers.展开更多
三维成像对空间目标测量、分类、识别等具有重要的意义。线性调频步进信号具有瞬时带宽较窄的特点,可获得较远的探测距离,在空间目标监视中具有优势。基于线性调频步进信号模型,提出了一种空间自旋目标时变三维成像的方法,并对由此产生...三维成像对空间目标测量、分类、识别等具有重要的意义。线性调频步进信号具有瞬时带宽较窄的特点,可获得较远的探测距离,在空间目标监视中具有优势。基于线性调频步进信号模型,提出了一种空间自旋目标时变三维成像的方法,并对由此产生的距离走动等问题进行了详细讨论。通过采用L型三天线雷达,首先分别获得各天线回波对应的高分辨距离像(high resolution range profile,HRRP)序列,然后利用Hough变换提取高分辨距离像序列中各个目标散射点的自旋运动特征,以获得各个散射点的自旋"轨迹",最后通过对不同干涉平面内的高分辨距离像序列进行干涉处理,获得各散射点在每一慢时间时刻的空间方位向和俯仰向位置,结合高分辨距离像序列获得的距离向信息即可准确重构散射点的时变空间三维位置。仿真实验验证了文中自旋目标时变三维成像方法的有效性。展开更多
基金Project(No.2009CB724003) supported by the National Basic Re-search Program (973) of China
文摘The geosynchronous circular synthetic aperture radar (GEOCSAR) is an innovative SAR system,which can produce high resolution three-dimensional (3D) images and has the potential to provide 3D deformation measurement.With an orbit altitude of approximately 36 000 km,the orbit motion and orbit disturbance effects of GEOCSAR behave differently from those of the conventional spaceborne SAR.In this paper,we analyze the effects of orbit errors on GEOCSAR imaging and interferometric processing.First,we present the GEOCSAR imaging geometry and the orbit errors model based on perturbation analysis.Then,we give the GEOCSAR signal formulation based on imaging geometry,and analyze the effect of the orbit error on the output focused signal.By interferometric processing on the 3D reconstructed images,the relationship between satellite orbit errors and the interferometric phase is deduced.Simulations demonstrate the effects of orbit errors on the GEOCSAR images,interferograms,and the deformations.The conclusions are that the required relative accuracy of orbit estimation should be at centimeter level for GEOCSAR imaging at L-band,and that millimeter-scale accuracy is needed for GEOCSAR interferometric processing.
文摘野外地质实践教学是高校地质类教学的重要组成部分,而教学安全是野外实践教学顺利进行的必要前提。为对教学路线进行全面、准确的风险评价,首先提出了针对山区野外地质实践教学实习路线的安全风险评价指标体系,其涵盖了滑坡风险、崩塌风险和滑倒风险3类常见风险;然后通过使用基于层次分析(analytic hierarchy process,AHP)法和合成孔径雷达差分干涉测量(differential interferometric synthetic aperture radar,D-InSAR)的滑坡风险量化模型进行滑坡风险评价,使用结合危岩判别的易发处数量-运动距离耦合评价模型进行崩塌风险评价,使用组合权重的优劣解距离法(technique for order preference by similarity to an ideal solution,TOPSIS)进行滑倒风险评价,并使用组合权重的优劣解距离法得到3类风险的综合评价结果,构建了山区野外地质实践教学实习路线安全风险综合评价方法;最后将该方法应用于链子崖实习路线。结果表明:链子崖实习路线风险值整体较低,处于“较安全”水平,但局部存在“较不安全”路段,需要特别关注。研究提出的评价方法具有可行性与合理性,可以为保障实习人员的安全提供科学参考,并为野外地质实践教学安全与风险综合评价方法提供借鉴。
基金supported by the China National SKA Programme(2020SKA0110300)the National Natural Science Foundation of China(NSFC,Grant Nos.12433012 and 12373097)the Guangzhou Science and Technology Funds(2023A03J0016)。
文摘The Square Kilometre Array(SKA)has the potential to revolutionize astronomical research through its unparalleled precision.A critical aspect of SKA imaging is the computation of the UVW coordinates,which must be accurate and reliable for the development of the SKA scientific data processor.Katpoint is the current method used to calculate UVW in Meer KAT.Using a pseudo-source,we employ a simple cross-product method to determine UVWs.In this study,we explore the applicability of Katpoint for SKA1-low and SKA1-mid and evaluate its precision.The conventional method,CALC/Omni UV,and Katpoint were quantitatively assessed through simulations.The results indicate that Katpoint exhibits substantial accuracy with MeerKAT compared to traditional techniques.However,its precision is slightly inadequate for the long baselines of SKA1.We improved the precision of Katpoint by identifying optimal offset values for pseudo-sources on the SKA1 telescope through simulation,finding a 0°.11 offset suitable for SKA1-Mid and a 0°.045 offset for SKA1-Low.Final result validations demonstrate that these adjustments render the computational accuracy fully comparable to the standard CALC/Omni UV method,which would meet the requirements of SKA high-precision imaging and offer a solution for high-precision imaging in radio interferometers.
文摘三维成像对空间目标测量、分类、识别等具有重要的意义。线性调频步进信号具有瞬时带宽较窄的特点,可获得较远的探测距离,在空间目标监视中具有优势。基于线性调频步进信号模型,提出了一种空间自旋目标时变三维成像的方法,并对由此产生的距离走动等问题进行了详细讨论。通过采用L型三天线雷达,首先分别获得各天线回波对应的高分辨距离像(high resolution range profile,HRRP)序列,然后利用Hough变换提取高分辨距离像序列中各个目标散射点的自旋运动特征,以获得各个散射点的自旋"轨迹",最后通过对不同干涉平面内的高分辨距离像序列进行干涉处理,获得各散射点在每一慢时间时刻的空间方位向和俯仰向位置,结合高分辨距离像序列获得的距离向信息即可准确重构散射点的时变空间三维位置。仿真实验验证了文中自旋目标时变三维成像方法的有效性。
