Influences of Atmospheric Turbulence on Image Resolution of Airborne and Space-Borne Optical Remote Sensing System

A new way is proposed to evaluate the influence of atmospheric turbulence on image resolution of airborne and space-borne optical remote sensing system, which is called as arrival angle-method. Applying this method, some engineering examples are selected to analyze the turbulence influences on image resolution based on three different atmospheric turbulence models quantificationally, for the airborne remote sensing system, the resolution errors caused by the atmospheric turbulence are less than 1 cm, and for the space-borne remote sensing system, the errors are around 1 cm. The results are similar to that obtained by the previous Friedmethod. Compared with the Fried-method, the arrival angle-method is rather simple and can be easily used in engineering fields.

Landslide data mosaicking based on an airborne laser point cloud and multi-beam sonar images

Landslides are one of the most disastrous geological hazards in southwestern China.Once a landslide becomes unstable,it threatens the lives and safety of local residents.However,empirical studies on landslides have predominantly focused on landslides that occur on land.To this end,we aim to investigate ashore and underwater landslide data synchronously.This study proposes an optimized mosaicking method for ashore and underwater landslide data.This method fuses an airborne laser point cloud with multi-beam depth sounder images.Owing to their relatively high efficiency and large coverage area,airborne laser measurement systems are suitable for emergency investigations of landslides.Based on the airborne laser point cloud,the traversal of the point with the lowest elevation value in the point set can be used to perform rapid extraction of the crude channel boundaries.Further meticulous extraction of the channel boundaries is then implemented using the probability mean value optimization method.In addition,synthesis of the integrated ashore and underwater landslide data angle is realized using the spatial guide line between the channel boundaries and the underwater multibeam sonar images.A landslide located on the right bank of the middle reaches of the Yalong River is selected as a case study to demonstrate that the proposed method has higher precision thantraditional methods.The experimental results show that the mosaicking method in this study can meet the basic needs of landslide modeling and provide a basis for qualitative and quantitative analysis and stability prediction of landslides.

SIFT-based automatic tie-points extraction for airborne InSAR images

The scale-invariant feature transform (SIFT) is often applied to extract tie-points for airborne SAR images. When a pair of airborne SAR images differs with look angles obviously, shadow sizes and shapes of same objects will differ obviously. In main and slave SAR images, key-points around shadows often match as tie-points, although they are not homologous points. The phenomenon worsens the performance of SIFT on SAR images. On the basis of SIFT, a modified matching method is proposed to decrease the number of incorrect tie-points. High-resolution airborne SAR images are used in Experiments. Experiment results show that the proposed method is very effective to extract correct tie-points for SAR images.

A two-step rectification algorithm for airborne linear images with POS data

Rectification for airborne linear images is an indispensable preprocessing step. This paper presents in detail a two-step rectification algorithm. The first step is to establish the model of direct georeference position using the data provided by the Po- sitioning and Orientation System (POS) and obtain the mathematical relationships between the image points and ground reference points. The second step is to apply polynomial distortion model and Bilinear Interpolation to get the final precise rectified images. In this step, a reference image is required and some ground control points (GCPs) are selected. Experiments showed that the final rectified images are satisfactory, and that our two-step rectification algorithm is very effective.

无人机稳像系统研究综述

针对无人机在飞行过程中会受到机身或环境的影响而造成航拍设备的抖动,对面向无人机平台的稳像系统进行分析。在简要介绍研究背景的基础上,主要从机械稳像和电子稳像2方面进行展开,系统介绍国内外研究现状和多种典型的稳像算法,分析无人机稳像系统未来可能发展的研究方向。结果表明,该研究对无人机航拍图像的增稳及不同场景下稳像方法的选取具有一定的指导作用。

机载光纤式成像差分吸收光谱仪测量区域大气污染应用研究

我国大气污染呈现出区域性和复杂性等特性,开展污染气体区域分布的立体监测,能够及时了解大气环境现状、研究分析影响大气质量的各种因素,指导大气污染控制措施。机载成像差分吸收光谱仪,是目前有效的污染气体区域分布遥感手段之一。该技术观测区域大,覆盖率高,最终可提供精细化的污染气体区域分布资料,实现污染分布及传输的可视化探测。以往机载成像差分吸收光谱仪采用整体式设计,需要占用飞机光学观察窗口,航空搭载需求苛刻、应用受限。为此提出了光纤式机载成像差分吸收光谱仪,采用光纤束传输方式,安装过程中对飞机改装需求小,极大的便利了机上安装和调试,适应了适航设备认证需求。该系统采用特制多芯光纤束结合Littow-offner结构光谱成像系统,具有光谱成像分辨率高、大视场、结构紧凑等优点。在此详细介绍了该设备性能参数,并利用该系统在芜湖市周边开展了区域污染遥感应用。应用过程中,针对光纤式成像差分吸收光谱仪,提出了数据处理算法。对采集到的太阳散射光谱进行反演得到污染气体的斜柱浓度,并利用大气传输模型计算大气质量因子,实现垂直柱浓度转化。最后结合飞机姿态位置信息,快速获取了芜湖市区及其周边上空的NO_(2)、SO_(2)的浓度分布,并进行了区域内污染源快速定位和传输过程分析。从反演结果来看,本次实验NO_(2)垂直柱浓度在实验区域存在4个高值点,SO_(2)垂直柱浓度在实验区域存在2个高值点,高值点附近均存在重工企业,结果与实际情况相符。并结合卫星数据评估二者交叉校验精度,二者呈现正相关,相关性系数为0.77。应用效果验证了光纤式成像差分吸收光谱仪的方案可行性,可为大气污染气体航空遥感技术推广提供参考,同时弥补了地面站点监测在空间尺度上以及卫星遥感在时间尺度上的不足。

基于LiDAR数据与光谱影像融合的单木提取方法

针对现有的机载数据单木分割方法对林型的普适度不高,尤其在高郁闭度阔叶林地带提取精度偏低的问题,选用海南省海口市热带阔叶林地带的光谱影像和LiDAR数据,先采用基于距离阈值的单木分割方法,利用高分光谱影像分割得到的树冠边缘,对初始探测树顶点进行位置约束。获得单木顶点的精确定位后,采用基于种子点的单木分割方法分割,完成了阔叶林的单木提取。结果显示,与已有的基于单木间相对间距单木分割方法相比,本研究通过选取最佳分割尺度结合光谱影像进行精确定位,改善了原有单一尺度分割方法导致的过分割现象,将单木识别精确率由0.67提升至0.92。该方法在使用遥感对森林单木进行分割工作中,可以更好地识别单木,对不同林型适用度较高,可以为后续的单木信息提取工作提供数据基础。

基于激光雷达与机载光电成像融合的高速轨道形变检测系统设计

高速轨道形变是指高速铁路轨道在运营过程中由于列车荷载、温度变化、地基沉降等因素而发生的变形现象,极大影响了高速铁路车辆的行驶安全性,为此,设计了基于激光雷达与机载光电成像融合的高速轨道形变检测系统;通过激光发射器、激光信号接收器的结构设计与组装,实现激光雷达成像模块的设计,从无人机、光电摄像机、云台等方面,完成对机载光电成像模块的设计,实现图像数据的融合处理;在硬件优化系统的支持下,生成高速轨道的激光雷达与机载光电图像,经过去噪、畸变校正、去雾等操作,完成对初始图像的预处理;采用加权融合的方式,得到激光雷达与机载光电融合图像,并提取融合图像的边缘特征,计算高速轨道位置坐标,通过坐标计算结果与轨道初始结构数据的比对,输出高速轨道形变的检测结果;实验结果表明:所设计系统的平均状态误检率为2.3%,形变量检测误差平均值为0.15 mm,具有良好的检测能力。

复杂背景下红外弱小运动目标检测半仿真数据集

红外弱小运动目标检测是空中红外探测的核心技术之一,且一直是光电探测领域研究的热点问题,尤其是复杂背景下弱小运动目标检测,尚缺乏有效的技术解决途径。针对当前红外弱小运动目标检测领域数据规模小、场景类型丰富程度不足的问题,本数据集面向空中红外探测设备远距离探测空中飞行目标应用,借助小型无人机平台搭载红外探测设备,通过实地拍摄、数据加工及仿真目标嵌入处理等,提供了一套数据规模大、场景类型丰富的复杂背景下红外弱小运动目标检测半仿真数据集。图像数据采集中设置多种实验条件,以求尽可能地全方位模拟典型应用场景:为体现探测平台与目标的相对高度,设置了仰视、平视和俯视三种拍摄视角;为模拟不同场景类型,数据集获取场景涵盖了天空、水面、植被、建筑物等多种场景;为模拟被探测目标不同运动情况,数据集中采用分段拟合的方式,设置了不同复杂程度的目标运动轨迹;本数据集仿真了不同灰度分布、不同信号强度的弱小运动目标,并高质量地嵌入图像背景中。本数据集共计350段数据、150185帧图像,标注文件中给出目标坐标位置的详细标注信息。本数据集可为复杂背景下红外弱小运动目标检测、跟踪等研究提供基础数据。

面向机载分布式光电的图像拼接算法

随着航空无人系统技术的迅猛发展,分布式机载图像拼接技术已成为备受瞩目的研究领域。本文针对分布式机载图像拼接中存在的视差大和空间几何变换关系复杂等问题,在APAP图像拼接算法基础上提出了一种改进算法。该算法采用变形处理、线性化单应平滑外推至全局性变换以及网格划分法等方法,有效消除了模糊重影、减少边缘处投影失真,提高算法运行效率。在多个场景下的实验中,该算法表现出更小的对齐误差和更高的图像质量指标,包括均方根误差、峰值信噪比、结构相似度和图像熵等。在进行大规模图像拼接时,该改进算法能够实现154张图像的大规模拼接,得到10 k×10 k的高分辨率全景图像,拼接耗时为138 s。因此,该改进算法具有重要的实际应用价值,可用于分布式机载图像拼接的实际应用中。

机载DOM面向对象的改扩建公路沿线主要地物提取研究

针对改扩建公路沿线地物信息提取难度大、工期紧等问题,以成南高速扩容项目(成都螺狮坝立交附近)的机载高分辨率DOM遥感影像为研究对象,运用KNN、CART、SVM等3种面向对象分类方法,对该扩容高速沿线左右约300 m范围内带状区域进行主要地物信息提取与分类研究。结果表明:1)最优分割尺度的确定是一个复杂过程,且受到多种因素的制约,通过运用ESP工具简化获取最优分割尺度,并取得了较好影像分割效果;2)3种面向对象分类结果基本满足了改扩建公路工程前期规划、设计和施工建设的精度要求,3种方法在基于同一训练样本与验证样本数据基础上,就分类精度而言,SVM>CART>KNN,就具体地物而言,居民用地、交通运输用地、植被和水体等地物的分类精度相对较高,裸地、大棚和其他等地物的分类精度相对较低;3)3种分类方法技术先进、经济高效,且对于改扩建公路沿线地物自动化智能化提取及其在数字化交通中的应用具有显著的实际价值。

基于小波变换的机载雷达测绘遥感影像信息数据融合方法

在融合机载雷达测绘遥感影像信息数据的过程中,由于原始机载雷达测绘遥感影像反馈信号在频域分布上具有多元化的属性,导致融合后影像的质量相对较低。为此,文章提出基于小波变换的机载雷达测绘遥感影像信息数据融合方法。该方法通过在小波变换设置了以频率为基准的窗口函数,并结合遥感影像反馈信号所处频域与频率函数状态之间的关系,建立了待分析遥感影像信号与频率窗内的高频频域分布参数之间的乘积关系,从而得到所需的信号频谱特性,在进行机载雷达测绘遥感影像信息数据融合阶段,结合遥感影像反馈信号与有限区域范围之间的关系,对其进行适应性融合。测试结果表明,融合后影像在完整度、清晰度以及综合质量方面均处于较高水平。

Multispectral imaging systems for airborne remote sensing to support agricultural production management

This study investigated three different types of multispectral imaging systems for airborne remote sensing to support management in agricultural application and production.The three systems have been used in agricultural studies.They range from low-cost to relatively high-cost,manually operated to automated,multispectral composite imaging with a single camera and integrated imaging with custom-mounting of separate cameras.Practical issues regarding use of the imaging systems were described and discussed.The low-cost system,due to band saturation,slow imaging speed and poor image quality,is more preferable to slower moving platforms that can fly close to the ground,such as unmanned autonomous helicopters,but not recommended for low or high altitude aerial remote sensing on fixed-wing aircraft.With the restriction on payload unmanned autonomous helicopters are not recommended for high-cost systems because they are typically heavy and difficult to mount.The system with intermediate cost works well for low altitude aerial remote sensing on fixed-wing aircraft with field shapefile-based global positioning triggering.This system also works well for high altitude aerial remote sensing on fixed-wing aircraft with global positioning triggering or manually operated.The custom-built system is recommended for high altitude aerial remote sensing on fixed-wing aircraft with waypoint global positioning triggering or manually operated.

A Novel Imaging Algorithm for Airborne Bistatic Squint SAR with Unparallel Trajectories

A novel analytical imaging algorithm is proposed for the strip-map mode of airborne bistatic squint SAR with unparallel trajectories. The algorithm derives the two-dimensional （2D） spectrum formula of the point target echo by using the contribution ratios of Doppler frequency modulation ratios of the transmitter and receiver as the weighting coefficients. Through decoupling the target position against the tracks of the transmitter and receiver, the range parameter and the azimuth one in the spectrum formula are separated. In 2D frequency domain, 2D Chirp-Z transform （2D-CZT） is applied to correcting the migrations of the echo along the range and azimuth after the bistatic deformation term has been compensated, so the target image is precisely focused. The advantage of the algorithm is easy to be expanded to the virtual wide swath by blocking the radar data along the range and azimuth to limit the 2D residual migrations. Simulation results confirm the validity of the 2D-CZT algorithm.

Design of a wide-field target detection and tracking system using the segmented planar imaging detector for electro-optical reconnaissance

Detecting and tracking multiple targets simultaneously for space-based surveillance requires multiple cameras,which leads to a large system volume and weight. To address this problem, we propose a wide-field detection and tracking system using the segmented planar imaging detector for electro-optical reconnaissance. This study realizes two operating modes by changing the working paired lenslets and corresponding waveguide arrays： a detection mode and a tracking mode. A model system was simulated and evaluated using the peak signal-to-noise ratio method. The simulation results indicate that the detection and tracking system can realize wide-field detection and narrow-field, multi-target, high-resolution tracking without moving parts.

小型机载高光谱成像仪在高山峡谷地区遥感地质岩性解译应用

【研究目的】水利工程项目通常位于地势险峻的山区,交通不便、环境恶劣,勘察工作十分艰苦。同时,视界限制使地质人员不能整体上掌握地质体的面貌,尤其在高山峡谷地区,人力、物力及时间成本耗费巨大。高光谱遥感技术在地质领域中的应用主要集中在地物分布反演方向,通过未知地物与已知矿物之间相同的特征吸收峰来判定地物种类,利用其极高的光谱分辨率、空间分辨率和“图谱合一”的特性,可对高山峡谷区的地物目标进行精细分类,从而提高地质调查工作的效率,降低风险。【研究方法】中水北方勘测设计研究院利用中国地质调查局南京地质调查中心自主研发的高效率小型机载高光谱成像光谱仪,首次对位于甘南藏族自治州迭部县高山峡谷地带的工作区进行高光谱遥感对地探测,获取了工作区航空高光谱影像数据。采用最小噪声分离法、波段比值分析法对高光谱遥感数据进行岩性解译。【研究结果】结果表明:以白龙江为界,以北大部分为板岩及第四系黄土,以南则大部分为灰岩。解译结果与已知区域地质图岩性分布一致。【结论】本次研究验证了国产高光谱成像仪的可靠性与实用性,同时提高了水利工程前期地质勘查工作的效率和水平,并提供了险要地形地质勘察的一手资料。

机载多维度SAR航空观测系统实验初步进展

随着合成孔径雷达(SAR)技术的发展,从极化、频率、角度和时相等多个维度空间联合观测成为SAR发展的重要趋势,但维度联合观测的系统与实验少有报道。该文概要介绍了机载多维度SAR(MSJosSAR)航空观测系统的能力,归纳总结了该系统的技术特点。提出多维度SAR一致性成像方法,实现多波段成像后的配准精度优于1个像元。分析了多波段极化角度特征谱、多方位角层析3维结构重建、多时相相干变化检测等3种SAR多维观测量的初步实验结果,验证了系统的多维观测能力。

图像边缘权重优化的最小生成树分割提取

针对无监督图像分割方法对噪声敏感而导致图像建模困难、分割结果准确率低等问题,该文提出一种图像边缘权重优化的最小生成树分割提取方法。首先,利用L0梯度最小值平滑处理噪声再结合Otsu优化Canny边缘检测,得到更加准确的边缘信息;其次,重新设计权重函数,采用更加合理的色差空间构建加权图,通过改进分割准则优化物体合并与区分过程;最后,选择不同类型图片进行抗噪性、分割效果实验。实验结果表明:相对于其他算法,该文算法的抗噪性能优秀,分割精度平均提升5.15%,过分割率平均下降32.07%,欠分割率平均下降2.69%。将其运用在实际航空遥感图像的河道湖泊提取中,所得结果相比其他主流算法结构更加完整,无关信息更少,抗噪性能更好。

阵列光束棱镜扫描光束指向及点云精度分析

在面阵扫描成像激光雷达中,阵列光束照明与棱镜扫描相结合实现了高能量利用率、高分辨率和宽探测视场,但阵列子光束倾斜入射棱镜,破坏了光束传输的旋转对称性,棱镜对子光束偏转能力存在差异,规则光束阵列产生了形状畸变,导致光束指向误差,影响点云位置精度。首先,将阵列光束与棱镜结合的圆锥扫描方式分解为多角度入射多波束并行扫描,通过所有子光束的传输特征来综合表征阵列光束传输特征;然后,采用三维矢量光学方法推导了阵列光束在棱镜中的传输过程,建立了子光束指向变化与棱镜扫描角度的关系;最后,通过对机载激光雷达棱镜扫描成像过程的数值仿真,建立了光束指向变化与点云数据质量的联系。仿真结果表明:阵列光束(3×3)棱镜扫描系统在航高0.5 km时,光束阵列畸变导致平面误差RMS约为5 cm,并随航高呈线性变化;斜率约为0.1 m/km,并随着阵列光束规模和子光束角间距增加点云平面精度随之下降。通过对棱镜扫描过程中光束阵列畸变规律掌握,为后续机载飞行试验数据的校正、阵列光束结合多棱镜扫描系统的设计提供了基础。

一种机载面阵摆扫成像视轴路径规划与重叠率计算的新方法

机载面阵摆扫式成像系统需要足够高的帧间重叠率来避免因扫描过程中视轴的控制误差而导致的漏扫,这制约了成像系统在大速高比条件下的适应能力,限制了系统的成像幅宽。论文提出了一种视轴路径规划模型与重叠率计算的新方法,通过像球面投影的几何分析方法优化设计了成像系统视轴的扫描路径,并依据像球面中像面投影的方位旋转角度,建立了一种重叠率计算的新模型。经理论分析与仿真实验验证,在40°侧向凝视成像时,视轴稳定精度由2.93°提高到0.15°,相同速高比、单行5帧摆扫成像时,作业效率提高约32%。论文研究工作对推动机载摆扫成像技术向着宽视场、大速高比、高分辨率方向的进一步发展具有重要意义。