针对目前短临预报业务及科研需求,开发了新一代天气雷达基数据管理与个例整编应用系统。该系统采用VC++6.0编程语言和MSSQL Server 2008数据库开发技术对不同历史个例资料建立了相应的数据库,对基数据文件采取压缩后直接入库的方式,实...针对目前短临预报业务及科研需求,开发了新一代天气雷达基数据管理与个例整编应用系统。该系统采用VC++6.0编程语言和MSSQL Server 2008数据库开发技术对不同历史个例资料建立了相应的数据库,对基数据文件采取压缩后直接入库的方式,实现了省、市、县级天气预报人员、气象服务人员、人工影响天气业务人员和科研人员对基数据的实时高效查询和下载。系统提供了不同检索条件的查询与个例资料的实时查阅和实时、历史基数据和个例信息的下载功能。为各级天气预报人员更有效地开展短临预报业务提供了便捷,也为其他科研业务人员提供了详细和全面的观测数据支撑。投入业务运行一年来,效果良好,可以进一步推广应用。展开更多
When the saturation degree （SD） of space-borne SAR raw data is high, the performance of conventional block adaptive quantization （BAQ） deteriorates obviously. In order to overcome the drawback, this paper studies ...When the saturation degree （SD） of space-borne SAR raw data is high, the performance of conventional block adaptive quantization （BAQ） deteriorates obviously. In order to overcome the drawback, this paper studies the mapping between the average signal magnitude （ASM） and the standard deviation of the input signal （SDIS） to the A/D from the original reference. Then, it points out the mistake of the mapping and introduces the concept of the standard deviation of the output signal （SDOS） from the A/D. After that, this paper educes the mapping between the ASM and SDOS from the A/D. Monte-Carlo experiment shows that none of the above two mappings is the optimal in the whole set of SD. Thus, this paper proposes the concept of piecewise linear mapping and the searching algorithm in the whole set of SD. According to the linear part, this paper gives the certification and analytical value of k and for nonlinear part, and utilizes the searching algorithm mentioned above to search the corresponding value of k. Experimental results based on simulated data and real data show that the performance of new algorithm is better than conventional BAQ when raw data is in heavy SD.展开更多
Phase errors in synthetic aperture sonar (SAS) imaging must be reduced to less than one eighth of a wavelength so as to avoid image destruction. Most of the phase errors occur as a result of platform motion errors, fo...Phase errors in synthetic aperture sonar (SAS) imaging must be reduced to less than one eighth of a wavelength so as to avoid image destruction. Most of the phase errors occur as a result of platform motion errors, for example, sway yaw and surge that are the most important error sources. The phase error of a wide band synthetic aperture sonar is modeled and solutions to sway yaw and surge motion estimation based on the raw sonar echo data with a Displaced Phase Center Antenna (DPCA) method are proposed and their implementations are detailed in this paper. It is shown that the sway estimates can be obtained from the correlation lag and phase difference between the returns at coincident phase centers. An estimate of yaw is also possible if such a technique is applied to more than one overlapping phase center positions. Surge estimates can be obtained by identifying pairs of phase centers with a maximum correlation coefficient. The method works only if the platform velocity is low enough such that a number of phase centers from adjacent pings overlap.展开更多
文摘针对目前短临预报业务及科研需求,开发了新一代天气雷达基数据管理与个例整编应用系统。该系统采用VC++6.0编程语言和MSSQL Server 2008数据库开发技术对不同历史个例资料建立了相应的数据库,对基数据文件采取压缩后直接入库的方式,实现了省、市、县级天气预报人员、气象服务人员、人工影响天气业务人员和科研人员对基数据的实时高效查询和下载。系统提供了不同检索条件的查询与个例资料的实时查阅和实时、历史基数据和个例信息的下载功能。为各级天气预报人员更有效地开展短临预报业务提供了便捷,也为其他科研业务人员提供了详细和全面的观测数据支撑。投入业务运行一年来,效果良好,可以进一步推广应用。
文摘When the saturation degree （SD） of space-borne SAR raw data is high, the performance of conventional block adaptive quantization （BAQ） deteriorates obviously. In order to overcome the drawback, this paper studies the mapping between the average signal magnitude （ASM） and the standard deviation of the input signal （SDIS） to the A/D from the original reference. Then, it points out the mistake of the mapping and introduces the concept of the standard deviation of the output signal （SDOS） from the A/D. After that, this paper educes the mapping between the ASM and SDOS from the A/D. Monte-Carlo experiment shows that none of the above two mappings is the optimal in the whole set of SD. Thus, this paper proposes the concept of piecewise linear mapping and the searching algorithm in the whole set of SD. According to the linear part, this paper gives the certification and analytical value of k and for nonlinear part, and utilizes the searching algorithm mentioned above to search the corresponding value of k. Experimental results based on simulated data and real data show that the performance of new algorithm is better than conventional BAQ when raw data is in heavy SD.
文摘Phase errors in synthetic aperture sonar (SAS) imaging must be reduced to less than one eighth of a wavelength so as to avoid image destruction. Most of the phase errors occur as a result of platform motion errors, for example, sway yaw and surge that are the most important error sources. The phase error of a wide band synthetic aperture sonar is modeled and solutions to sway yaw and surge motion estimation based on the raw sonar echo data with a Displaced Phase Center Antenna (DPCA) method are proposed and their implementations are detailed in this paper. It is shown that the sway estimates can be obtained from the correlation lag and phase difference between the returns at coincident phase centers. An estimate of yaw is also possible if such a technique is applied to more than one overlapping phase center positions. Surge estimates can be obtained by identifying pairs of phase centers with a maximum correlation coefficient. The method works only if the platform velocity is low enough such that a number of phase centers from adjacent pings overlap.
