无人机影像自检校光束法区域网平差精度分析

无人机遥感系统一般搭载非量测型数码相机,该类型相机的内参数未知或部分未知,获取的影像存在畸变。设备运输、航摄飞行等动态环境因素对相机内参数的稳定性产生影响,导致区域网平差的精度降低,甚至平差失败。对无人机影像的系统误差源进行分析,给出了畸变差改正模型,自检校光束法平差模型及平差精度估计公式。试验证明:自检校光束法区域网平差可以减弱数码相机内参数变化对平差精度的影响,提高地面控制点、影像外方位线元素的定位精度。     

基于三维DLT方法的非量测数码相机检校

低空无人机遥感系统应用日益广泛,其一般搭载传感器为非量测型数码相机,为了保证测量精度必须进行相机检校,以确定其内方位元素和畸变差系数。采用室外三维控制场的DLT(直接线性变换)方法,编制了基于三维DLT方法的非量测型相机的检校软件,该软件具备相机检校参数解算和物方空间坐标解算功能。对于室外三维控制场的测量数据和一海岛的无人机航摄数据,分别使用和不使用相机检校参数进行处理,试验结果显示使用检校参数可以获得更好地测量精度,表明了室外三维检校场方案和编制的相机检校软件是正确可行的,可实现非量测数码相机的检校。     

无控制点条件下的测绘卫星影像RPC区域网平差

针对无控制点条件下测绘卫星影像区域网平差迭代难以收敛和影像重叠区域存在接边误差的问题,提出了一种基于基准影像的区域网平差方法。利用资源三号卫星影像进行无控制点条件下的区域网平差时,相对于LEVENBERG MARQUARDT算法,基于基准影像的区域网平差方法能得到较为稳定的平差解和较好的平差精度。为进一步验证方法的适用性,利用异轨长条带天绘一号卫星影像数据进行无控制点条件下的区域网平差。实验结果表明,基于基准影像的区域网平差方法显著优化了卫星影像的内部符合精度,为下一级卫星测绘产品的高精度处理奠定了基础。     

稀少控制点异轨立体卫星影像区域网平差应用研究

结合PixelGrid软件应用,分析了异轨立体卫星影像区域网平差原理。在稀少控制点情况下,针对大范围高分辨率立体卫星遥感影像的区域网平差处理,提出了5种解决方案,并进行了实验分析,得出明确的结论。     

SZF型方位传感器方位定标测试方法

文中简要介绍了SZF型方位传感器的主要组成及工作原理,针对方位传感器在实验室内如何定标与测试给出了行之有效的计算机自差校正方案及实施方法,经过了大量的实际应用,该方法已经成为SZF型传感器的定标测试过程的重要步骤.     

水下目标方位估计的一种新方法

矢量传感器是一种新型水声传感器。介绍了应用矢量传感器确定目标方位的理论和方法，给出了仿真和实验研究结果，讨论了矢量传感器具体体积小、输出信号多、抗各向同性干扰等特性。最后定性地分析了目标方位的方位估值误差。     

海洋重力测量中系统误差的补偿研究

本文在分析总结海洋重力测量中的主要误差源基础上,从纯数学角度建立起能够反映海洋重力观测中系统误差变化规律的误差模型及其相应的测线网平差模型,分别提出两种补偿系统误差的解算方法,即自检校平差法和验后补偿法,并详细讨论了求解过程中的秩亏现象、误差模型的选择、附加参数权的确定以及系统误差补偿效果的显著性检验等一系列应用中的具体问题,最后本文使用一个实际观测网数据验证了两种补偿方法的有效性和可靠性。     

HYCOM模式对赤道及北太平洋海表温度的模拟

根据2种海气通量数据集(COADS、ECMWF)和2种海气通量块体参数化方案(常数块体参数化方案和非常数块体参数化方案)的不同结合,构成4组数值实验,使用HYCOM数值模式分别模拟了赤道及北太平洋的气候态海表温度。实验结果表明:(1)非常数块体参数化方案优于常数块体参数化方案;在太平洋40°N～20°S区域内,采用前者得到的年平均海表温度比Pathfinder卫星资料高约0.21℃,而采用后者得到的年平均海表温度比Path-finder卫星资料高约0.63℃。(2)HYCOM数值模式很好地模拟了赤道及北太平洋的气候态海表温度变化及西太平洋暖池空间分布的月变化。特别是实验2(采用COADS数据集和非常数块体参数化方案),在太平洋40°N～20°S区域内,冬、春两季平均SST仅比Pathfinder卫星数据集高0.02℃。(3)不同海气通量数据会对模拟结果产生明显影响。对比采用COADS数据集的实验2结果与采用ECMWF数据集的实验4结果可以发现,在模拟区域的西北部,实验2比实验4的年平均SST高约1℃;在模拟区域的东南部,实验4比实验2的年平均SST高约1℃。两者差的最大值出现在58°N、140°E附近及中国渤海,实验2比实验4的年平均SST高约4℃。     

水边线等高条件控制下的空中三角测量

针对海岸带和海岛礁稀少控制区域摄影测量定位问题,将水边线等高约束条件应用于区域网平差中,提出了一种海岸带水边线等高条件控制下的光束法区域网空中三角测量方法,精确确定摄影时影像的空间方位,进而提高海岸带和海岛礁稀少控制区域测图的几何定位精度。     

一种基于方位估计的双站被动声呐航迹关联方法

当探测区域存在多个目标时，双站被动声呐测向系统通过目标方位线交叉定位会产生多个交点，对被动声呐的测量方位进行关联即是剔除虚假交点，选择真实交点。在两被动声呐对目标方位保持连续跟踪的条件下，提出了一种利用方位预关联形成关联航迹对目标的位置和方位值进行估计，根据估计值与传感器实测方位值的偏差大小来判定预关联正确性的决策规则，结合海上实验数据仿真验证了方法的有效性。     

Short-crested wave interaction with a concentric porous cylindrical structure

In this paper, theoretical study is carried out to investigate the general 3D short-crested wave interaction with a concentric two-cylinder system. The interior cylinder is impermeable and the exterior cylinder is thin in thickness and porous to protect the interior cylinder. Both cylinders are surface-piercing and bottom mounted. Analytical solution is derived based on the linear potential theory. The effects of the wide range wave parameters and structure configuration including porosity of the exterior cylinder and the annular spacing on the wave forces, surface elevations and the diffracted wave contours are examined.     

近岸波浪折射-绕射-破波耗散联合模式的有限元数值研究

建立了近岸波浪折射-绕射-破波耗散的有限元数值模式。采用的有限元方法为改进的混合元法,其中外域开边界条件得到改进,内域有限元为伽廖金有限元。用理论解检验了所建立的数值模式,并将该模式应用到一个模型港湾。     

Wave interaction with a semi-porous cylindrical breakwater mounted on a storage tank

The interaction of linear water waves with a semi-porous cylindrical breakwater surrounding a rigid vertical circular cylinder mounted on a storage tank is investigated theoretically. The cylindrical breakwater structure is porous in the vicinity of the free-surface, while at some distance below the water surface it becomes impermeable. Under the assumptions of linearized potential flow, the coupled problem of flow in the interior and exterior fluid regions is solved by an eigenfunction expansion approach. Analytical expressions are obtained for the wave motion in both the interior and exterior flow regions. Numerical results are presented which illustrate the effects of the various wave and structural parameters on the hydrodynamic loads and interior and exterior wave fields. It is found that for certain parameter combinations the semi-porous, cylindrical breakwater may result in a significant reduction in the wave field and hydrodynamic forces experienced by the interior structure.     

分离式点结构光测量系统及其检定方法

传统点结构光传感器将激光器和CCD传感器固定在精密背架上,限制了其测量范围。将激光器与CCD摄像机分离,并给出了标定方法。通过实验,验证了该方法的可行性,拓展了点结构光传感器的应用领域。     

Computation of wave-making resistance of a catamaran in deep water using a potential-based panel method

This paper presents a potential-based boundary element method for solving a nonlinear free-surface flow problem for a Wigley catamaran moving with a uniform speed in deep water. Since the interior flow of each monohull of the catamaran is different from the exterior flow, both monohulls must be considered as lifting bodies. The pressure Kutta condition is imposed at the trailing-edge of the lifting body by determining the dipole distribution, which generates required circulation on the lifting part. The effects of wave interference and hull separation on the hydrodynamic characteristics of the catamaran hull are analyzed and the validity of the computer scheme is examined by comparing the wave resistance with the numerical results of others. The present method could be a useful design tool for screening the suitable combinations of hull parameters and hull spacing at the preliminary design stage of catamaran hull.     

海岸带水边线等高条件控制下的航空影像外部定向

提出了一种基于海岸带水边线等高条件的航空影像外部定向方法,该方法将局部区域水边线上各点的高程值相等作为控制条件,在立体像对的外部定向中,引入这些等高点,和其他平高控制点一起参加平差,计算立体像对的绝对方位元素.实验证明,该方法能够有效地提高航空影像的外部定向精度,尤其是高程的定位精度,提高了海岸带地形的测图精度.     

Wave Action on Structures of Combined Cylinders

1.Introduction Owingtoitssignificanteffectofreductionofwaveloadsandwaverun up,theperforatedwallon anarrayofcylindricalstructureshasreceivedconsiderableattentioninrecentyears.Manyresearches havebeencarriedoutinthisfield.Anexactsolutionforthediffractionoflinearwaterwaveswithan arrayofimpermeablecylinderswasfirstgivenbySpringandMonkmeyer(1974)usinganeigenfunction expansionapproach.Subsequently,LintonandEvans(1990)madeamajorsimplificationtothetheo ry,whichallowedthenear fieldquantitiessuchasload…     

波浪与外壁透空双方形沉箱相互作用

在线性波浪理论下,利用复合边界元素法(composite BEM)数值解析在等水深、规则波浪入射二种外壁透空双方形沉箱的无因次波力及Kd绕射分布图,并分别与其他研究者所作双圆筒内、外圆柱无因次波力及绕射分布图的计算结果进行比较,都说明本模式的合理性和可行性。在考虑不同透水参数下,分别计算波浪作用在内、外结构物的波力及沉箱四周绕射系数大小分布图。计算结果显示:波浪作用于外壁透空全透水双方形沉箱,外方柱无因次最大波力值会随着透水参数增加而降低;内方柱无因次最大波力值则随着透水参数增加而增加。本研究结果可供设计外海透水方形沉箱结构交互作用参考。     

A mathematical model of calculating local tsunami wave source constraints and propagation

This paper presents a local tsunami simulation, including the initial displacement field model of tsunami source and tsunami wave propagation model. We deduced the tsunami wave equation; applied the ma...     

A quantitative striping removal algorithm for HY-1 CCD data

Striping is a common phenomenon in remote sensing imagery acquired by most spaceborneand airborne multispectral sensors. In contrast to the destriping of the images of optoelectronic mechanical scanners, fewer work has been done for push-broom CCD images. Based on the characteristics of HY -1 push-broom multispectral CCD camera and its prelaunch radiometric calibration results, the striping features are analyzed and a quantitative striping removal algorithm is proposed. The algorithm is to obtain the inter-detector equalization curves to reflect the differences between detectors by statistic analysis of the satellite imagery data set, and image stripes arising from the nonuniformity of the detectors of the CCD array can be removed using the estimated equalization curves. The preliminary results show that this method can effectively remove the stripes and preserve the radiometric accuracy of the raw data at the same time.