Linear spectral unmixing algorithm for modelling suspended sediment concentration of flash floods,upper Tekeze River,Ethiopia

Flash floods are the highest sediment transporting agent,but are inaccessible for in-situ sampling and have rarely been analyzed by remote sensing technology.Laboratory and field experiments were done to develop linear spectral unmixing(LSU) remote sensing model and evaluate its performance in simulating the suspended sediment concentration(SSC) in flash floods.The models were developed from continuous monitoring in the laboratory and the onsite spectral signature of river bed sediment deposits and flash floods in the Tekeze River and in its tributary,the Tsirare River.The Pearson correlation coefficient was used to determine the variability of correlations between reflectance and SSCs.The coefficient of determination(R2) and root mean square of error(RMSE) were used to evaluate the performance of the generated models.The results found that the Pearson correlation coefficient between SSCs and reflectance varied based on the level of the SSCs,geological colors,and grain sizes.The performance of the LSU model and empirical remote sensing approaches were computed to be R2=0.92,and RMSE=±0.76 g/1 in the Tsirare River and R2=0.91,and RMSE=±0.73 g/1 in the Tekeze River and R2=0.81,RMSE=±2.65 g/l in the Tsirare river and R2=0.76,RMSE=±10.87 g/l in the Tekeze River,respectively.Hence,the LSU approach of remote sensing was found to be relatively accurate in monitoring and modeling the variability of SSCs that could be applied to the upper Tekeze River basin.     

Assessing plantation canopy condition from airborne imagery using spectral mixture analysis and fractional abundances

Pine plantations in Australia are subject to a range of abiotic and biotic damaging agents that affect tree health and productivity. In order to optimise management decisions, plantation managers require regular intelligence relating to the status and trends in the health and condition of trees within individual compartments. Remote sensing technology offers an alternative to traditional ground-based assessment of these plantations. Automated estimation of foliar crown health, especially in degraded crowns, can be difficult due to mixed pixels when there is low or fragmented vegetation cover. In this study we apply a linear spectral unmixing approach to high spatial resolution (50 cm) multispectral imagery to quantify the fractional abundances of the key image endmembers: sunlit canopy, shadow, and soil. A number of Pinus radiata tree crown attributes were modelled using multiple linear regression and endmember fraction images. We found high levels of significance (r² = 0.80) for the overall crown colour and colour of the crown leader (r² = 0.79) in tree crowns affected by the fungal pathogen Sphaeropsis sapinea, which produces both needle necrosis and chlorosis. Results for stands associated with defoliation and chlorosis through infestation by the aphid Essigella californica were lower with an r² = 0.33 for crown transparency and r² = 0.31 for proportion of crown affected. Similar analysis of data from a nitrogen deficient site produced an outcome somewhat in between the other two damaging agents. Overall the sunlit canopy image fraction has been the most important variable used in the modelling of forest condition for all damaging agents.     

基于重力场模型的平均扰动场元的严密计算方法

卫星重力技术的进步为建立高精度的全球重力场模型提供了可能，该技术包括卫星测高、卫星重力梯度和卫星跟踪卫星等。而在建立扰动场模型的过程中一般要采用移去—恢复技术，该技术的核心是从已知的重力数据中减去根据参考重力场模型计算的扰动场元，并在最后的成果中加入移去部分对应的扰动场元。但在移去、恢复的过程中往往利用扰动场元在格网中心点的值乘以菜平滑因子代替扰动场元在该格网上的平均值，不可避免地引入了系统误差。从勒让德微分方程和勒让德函数的定义出发，详细研究了利用重力场模型计算扰动场元在格网上的平均值的方法，该方法在利用卫星测高资料反演海域重力异常中的应用表明，重力异常的精度得到了进一步提高。     

共聚焦点道集偏移速度建模

偏移速度建模可在多种道集实现.基于等时原理和差异时移分析,提出了共聚焦点道集偏移速度建模方法.偏移速度的更新是利用约束参数迭代反演实现,模型的参数化主要依据实际情况而定.为适应横向变速,选用了垂直速度梯度参数.模型试算表明:偏移速度相对误差在0.25%范围内,反射层深度误差小于10m.     

宽带约束地震反演在兰尕地区储层预测中的应用

兰尕背斜带处于塔河油田南部,具有发育非背斜圈闭的条件,勘探程度较低,适用于宽带约束地震反演技术进行储层预测。作者介绍了宽带约束稀疏脉冲反演技术的基本原理、实现方法以及反演流程,并在兰尕地区首次利用约束稀疏脉冲反演技术进行了储层预测,反演过程中运用了9口井进行约束。将反演结果与井真实情况相对比,上油组、中油组与钻井、测井解释储层吻合较好,下油组顶面吻合较好,内部及底部与钻井有一定差异。根据反演结果圈定了砂体发育带,确定了岩性圈闭,并最终落实了钻井目标。该方法在勘探程度比较低的地方可以较准确地预测储层岩性和展布规律,对油田的进一步勘探开发,以及降低勘探开发风险有一定的指导意义。     

附不等式约束平差的理论与方法研究

附不等式约束平差能充分利用已有的各种知识和信息,因而越来越得到关注,它在GPS数据处理、变形监测及方差估计等领域中都得到广泛的应用。目前,国内外对附不等式约束平差问题进行大量研究,文中主要综述附不等式约束平差问题的最新研究成果,系统介绍附不等式约束平差的理论,同时探讨附不等式约束平差的发展方向。     

一种偏振定标单元方位角误差的约束非线性最小化优化定标方法

偏振定标单元(Polarization Calibration Unit, PCU)对于定标由偏振系统和天文望远镜产生的仪器偏振至关重要, 然而偏振定标单元 中偏振元件光轴的方位角误差是限制定标精度的主要因素之一. 为解决该问题, 提出了一种基于约束非线性最 小化优化的方位角误差定标方法, 该方法具有定标精度高、定标速度快的优点. 首先将偏振定标单元中的线性 偏振片和四分之一波片的光轴方位角误差设置为两个待优化的自由变量, 然后利用产生和测量的Stokes参数 以及偏振定标获得的响应矩阵定义优化目标函数, 最终使用约束非线性最小化优化方法来确定 两个偏振元件的方位角误差. 分别从理论模拟和实际测量两个方面对优化方法进行了验证, 实验结果表明, 该 优化方法能够成功获得上述两个方位角误差, 精度分别优于2.79$''$和2.72$''$. 此外, 从理论上 计算分析了不同方位角误差对各Stokes分量的影响情况. 该优化方法有望应用到我国太阳望远镜中偏振定标 装置的误差定标及研制之中.     

县域耕地保有量目标约束机制及预测研究——以广西灌阳县为例

区域差异性导致各地耕地保护的目标不同,县域耕地保有量预测目标是否合理关系到区域和全局的耕地保护压力程度,影响着耕地保有量的合理预测,对有效遏止圈地现象至关重要。在耕地外部性特征基础上提出耕地保有量外部性连环效应,并据此效应建立县域耕地保有量预测目标约束机制;通过分析灌阳县在上轮规划耕地保护情况和耕地保有量现状,将灌阳县耕地保有量预测目标定位为耕地均量动态平衡;预测规划目标年灌阳县耕地保有量目标及相关单项指标。     

玉兔号月球车巡视点矿物丰度及粒径分布高光谱反演

矿物的类型、丰度及其粒径分布对理解月球和行星表面曾经存在过怎样的地质演化过程具有重要的意义。本文提出基于辐射传输模型和稀疏分解模型反演矿物丰度及其粒径分布的方法,利用辐射传输模型计算各矿物端元不同粒径的单次散射反照率以构建解混光谱库,然后基于稀疏分解算法得到在每个可观测像元的端元最优丰度和粒径分布。利用实验室测量数据进行验证,表明本文方法具有较高的精度。最后根据玉兔号月球车的实地测量光谱数据,利用本文方法获得了其矿物的丰度及粒径分布,结果显示,辉石、橄榄石、斜长石、熔融玻璃和钛铁矿的丰度在4个观测点的平均丰度分别为28.1%、4.5%、39%、28%、0.4%,辉石的平均粒径为166.02μm,橄榄石为8.34μm,斜长石为196.31μm,熔融玻璃为44.21μm,一定程度上表明在这些观测点不同矿物对太空风化的响应不同。     

新型全栓接H型钢梁柱节点滞回性能研究

提出一种新型全栓接H型钢梁柱节点。为研究节点的滞回性能,采用立式加载方案对4个不同构造方式的新型和传统全栓接H型钢梁柱节点进行拟静力试验,分析各试件的节点破坏模式、P-Δ滞回曲线、M-θ骨架曲线、承载力及延性性能。结果表明:强轴新型全栓接节点与传统全栓接节点相比,滞回曲线、骨架曲线以及各项力学性能指标基本相同。弱轴新型全栓接节点与传统全栓接节点相比,具有更好的滞回性能、更高的延性和更强的承载力,其屈服承载力、极限承载力及延性分别增加了38%、35%和32%。