支持SAR系统高分辨率实时成像的实时系统解决方案

随着信息技术的发展 ,用于军事、地理、自然灾害扫描探测的合成孔径雷达系统 (SAR)对其成像能力的分辨率和实时显示要求越来越高 因此 ,研究具有自主知识产权的、可以实时处理高分辨率成像的实时系统迫在眉睫 针对实时数据接收、存储、显示和处理等核心问题 ,提出了一种实时系统解决方案 该方案通过对Linux内核的实时扩展 ,实现了可达到高处理机利用率的多任务实时调度方法 ,可支持混成调度 ;在应用层实现符合实时需求的功能模块 ;为DSP板开发实时驱动 ,形成了从硬件驱动层和操作系统层 ,直到应用软件层的完整实时计算体系

基于RTLinux构建机载SAR实时成像处理器嵌入式控制系统

面向地学处理的机载SAR实时成像处理器由一组连接在工业总线上的数据处理板和一个嵌入式主控子系统构成 ,成像处理器的总体设计对主控系统的实时性、稳定性及可扩展性提出了严格的要求 比较了传统的嵌入式工业控制系统的设计方法 ,设计并实现一个基于廉价的PC与RTLinux的主控系统 ,分析了主控系统的两个重点 :DSP宿主环境和RTLinux下的混合任务集 ,并通过给出一个RTLinux与Linux调度精度和误差的对比试验及其结果 ,证明了基于RTLinux的主控系统对支持细粒度调度方面的优越性

机载SAR实时成像系统中的数据可视化研究

SAR实时成像系统在国防等很多领域都有着重要的应用 ,系统对数据可视化方面的要求也越来越高 ,但目前国内对SAR实时成像系统的数据可视化方面的研究还不多 提出了一种针对SAR实时成像系统的新的数据可视化方案 ,并已在实际的飞行成像中得到了检验 新方案实时提供的信息更全面、更直观、可分析性更强 ,具有较强的信息表现能力和双向实时交互能力 ,能够较好地辅助对图像的在线分析 还对方案的重要组成部分———缩略图的原理和实现算法做了概括介绍

Optical dating of Holocene sand dune activities in the Horqin sand-fields in inner Mongolia；China；using the SAR protocol

IEECAS SKLLQG

Improving Ship Detection with Polarimetric SAR based on Convolution between Co-polarization Channels

The convolution between co-polarization amplitude only data is studied to improve ship detection performance. The different statistical behaviors of ships and surrounding ocean are characterized a by two-dimensional convolution function (2D-CF) between different polarization channels. The convolution value of the ocean decreases relative to initial data, while that of ships increases. Therefore the contrast of ships to ocean is increased. The opposite variation trend of ocean and ships can distinguish the high intensity ocean clutter from ships' signatures. The new criterion can generally avoid mistaken detection by a constant false alarm rate detector. Our new ship detector is compared with other polarimetric approaches, and the results confirm the robustness of the proposed method.

Validation of RADARSAT-2 fully polarimetric SAR measurements of ocean surface waves

C band RADARSAT-2 fully polarimetric (fine quad-polarization mode, HH+VV+HV+VH) synthetic aperture radar (SAR) images are used to validate ocean surface waves measurements using the polarimetric SAR wave retrieval algorithm, without estimating the complex hydrodynamic modulation transfer function, even under large radar incidence angles. The linearly polarized radar backscatter cross sections (RBCS) are first calculated with the copolarization (HH, VV) and cross-polarization (HV, VH) RBCS and the polarization orientation angle. Subsequently, in the azimuth direction, the vertically and linearly polarized RBCS are used to measure the wave slopes. In the range direction, we combine horizontally and vertically polarized RBCS to estimate wave slopes. Taken together, wave slope spectra can be derived using estimated wave slopes in azimuth and range directions. Wave parameters extracted from the resultant wave slope spectra are validated with colocated National Data Buoy Center (NDBC) buoy measurements (wave periods, wavelengths, wave directions, and significant wave heights) and are shown to be in good agreement.

On SAR wind speed ambiguities and related geophysical model functions

Recent investigations show that normalized radar cross sections for C-band microwave sensors decrease under high wind conditions with certain incident angles instead of increase, as is the case for low to moderate wind speeds. This creates the problem of ambiguities in high wind speed retrievals from synthetic aperture radar (SAR). In the present work, four geophysical model functions (GMFs) are studied, namely the high wind C-band model 4 (CMOD4HW), C-band model 5 (CMOD5), the high wind vertical polarized GMF (HWGMF_VV), and the high wind horizontal polarized GMF (HWGMF_HH). Our focus is on model behaviours relative to wind speed ambiguities. We show that, except for CMOD4HW, the other GMFs exhibit the wind speed ambiguity problem. To consider this problem in high wind speed retrievals from SAR, we focus on hurricanes and propose a method to remove the speed ambiguity using the dominant hurricane wind structure.

Speed ambiguity in hurricane wind retrieval from SAR imagery

Under strong ocean surface wind conditions, the normalized radar cross section of synthetic aperture radar (SAR) is dampened at certain incident angles, compared with the signals under moderate winds. This causes a wind speed ambiguity problem in wind speed retrievals from SAR, because two solutions may exist for each backscattered signal. This study shows that the problem is ubiquitous in the images acquired by operational space-borne SAR sensors. Moreover, the problem is more severe for the near range and range travelling winds. To remove this ambiguity, a method was developed based on characteristics of the hurricane wind structure. A SAR image of Hurricane Rita (2005) was analysed to demonstrate the wind speed ambiguity problem and the method to improve the wind speed retrievals. Our conclusions suggest that a speed ambiguity removal algorithm must be used for wind retrievals from SAR in intense storms and hurricanes.