框幅式航测相机中像移量对直接地理定位精度影响的研究

在航空摄影测量中,载机前向飞行和姿态旋转引起的像移模糊会为同名像点的量测引入误差,使共线方程偏离共线的条件,进而导致直接地理定位的精度下降。为定量分析像移对物点直接定位的影响,从摄影测量的共线方程出发,在充分考虑前向飞行和姿态旋转的条件下,建立了框幅式相机中CCD靶面各点像移量的数学模型。根据该模型计算出像移轨迹中的质心坐标和其对应的曝光时标,并以质心确定同名像点坐标,以中心曝光时间作为曝光时标以获得对应的外方位元素。仿真结果表明,在理想条件下,以上述方法进行双像前方交会的物方定位误差最大为0.12 mm,有效降低了像移对直接地理定位的影响。文中为分析框幅式航测相机中像移量对位置精度的影响和曝光时标的确定提供了理论依据。     

Vehicle Positioning Based on Optical Camera Communication in V2I Environments

Demand for precise vehicle positioning (VP) increases as autonomous vehicles have recently been drawing attention. This paper proposes a scheme for positioning vehicles on the move based on optical camera communication (OCC) technology in the vehicle-to-infrastructure (V2I) environment. Light-emitting diode (LED) streetlights and vehicle cameras are used as transmitters and receivers respectively. Regions of streetlights are detected and traced by examining images that are obtained from cameras of vehicles. Then, a scheme for analyzing visible light data extracted from the images is proposed. The proposed vehicle positioning scheme uses information on angles between vectors that are formed under the collinearity conditions between the absolute coordinates of at least three received streetlights, and the coordinates of an image sensor. The experiments are performed under stationary state and moving state at a speed of 5 and 20 km/h. To verify the reliability of the proposed scheme, a comparison is made between the actual and estimated location of the camera in the stationary state. In addition, the path of a moving vehicle and the estimated path of the vehicle are compared to check the performance of the scheme. The performance of the proposed technique is analyzed and experimental demonstration confirms that the proposed OCC-based VP scheme achieves positioning accuracy of under 1 m.     

基于一般线性模型的功能磁共振成像回归量正交化

针对功能磁共振成像（fMRI）模型回归量之间存在共线性的问题,提出了一种正交化的方法。首先,确定感兴趣以及待正交的回归量;其次,从待正交回归量中减去与感兴趣回归量相关的部分,使模型中共线的回归量正交分解为相互独立的部分,以此来消除共线性的影响。此外,还讨论和分析了正交化对一般线性模型的影响。最后,分别使用一些合成数据和当前一个流行的fMRI数据分析软件包——脑功能磁共振图像软件包（FSL）进行实验。实验结果表明,正交化方法可以消除模型中的共线性,并且提高感兴趣回归量的显著性,从而实现准确的脑功能定位,可以应用于对脑的基础研究和临床治疗。     

基于未知参数约束方程的多观测站交会模型

航空飞行试验中,经常采用多个光电跟踪测量系统对飞机及武器发射、航空装备性能鉴定等进行轨迹测量,文章利用共线条件建立多个光电跟踪测量系统测量模型,提出了一种新的基于未知参数约束方程的算法;该算法是在建立多台光电经纬仪的共线条件方程的基础上,加入测量距离的约束条件共同形成一组观测方程,经线性化后,在最小二乘准则下求解其最佳估计;该算法经过飞行试验证明能够有效地提高观测数据处理精度。     

Price determinants for remanufactured electronic products: a case study on eBay UK

In this paper, we analyse the market determinants of price differentials between new and remanufactured products in Electronics using data on purchases made on eBay UK. The empirical analysis is carried out by means of linear regression methods, which are capable of controlling for the presence of collinearity among the explanatory variables. Our empirical results suggest that the seller reputation, length of warranties, proxies of demand and supply of remanufactured products, duration, end day of product listings as well as the availability of return policies are important determinants of price differentials. Most importantly, we find that the seller identity plays an important role, as our empirical results are predominantly driven by transactions carried out by non-manufacturer-approved vendors.     

汇率变化与决定的数量分析

本文以实行浮动汇率制的加拿大、日本两国为例,尝试采用自回归建模方法分析汇率与其各影响因素间的数量关系,为均衡汇率的确定,更好地预测汇率的波动幅度与方向提供参考.     

应用Hough变换的炮射航空摄像机外参数估计方法

提出了一种基于Hough变换的航空摄像机外参数估计新方法。该方法使用共线条件方程描述摄像机成像关系,用图像与物方特征点之间的组合对外参数空间离散点进行投票,将得票最多的离散参数点确定为参数估计值。为解决共线条件方程的非线性以及外参数之间的相关性问题,采用迭代方式进行参数估计。与基于最小二乘原理的传统外参数估计方法不同,该方法不需要事先对图像与物方空间特征点进行配对,解决了传统最小二乘法的特征匹配难题,避免了最小二乘法对错误匹配的鲁棒性较差的缺点。分别使用仿真和真实航拍图像对算法的有效性进行了检验,结果表明:摄像机坐标估计误差小于15 m,姿态角误差小于1°。参数估计结果能够满足舰炮作战中对侦察摄像机外参数估计精度的要求。     

Plücker直线描述的空间后方交会

目的 现有的空间后方交会方法没有充分利用成像光线的几何拓扑关系,共线条件的几何约束性弱,提出基于Plücker坐标的空间后方交会方法.方法 将成像光线用Plücker直线表示,通过Plücker成像光线在空间中的螺旋位移,使得物点在像点和投影中心所确定的Plücker直线上,建立基于Plücker成像光线的共线条件方程.结果 针对小倾角航空与近景影像,本文方法与传统的欧拉角法相比求解得到的外方位元素最大线元素误差分别从0.88 m降到0.53 m,从0.06 m降到0.01 m;最大角元素误差分别从0.016 2弧度降到0.002 9弧度,从0.087弧度降到0.066弧度.针对大倾角影像,欧拉角法不收敛而本文方法能正确解算.结论 本文方法由于增强了模型的几何强度,获得了更高的定位精度,且对于大倾角影像也同样能够获得正确而稳定的外方位元素解算结果.