直线特征约束的资源3号卫星影像自检校平差

针对控制点获取较困难地区卫星影像定位精度不高的情况,对直线特征作为控制信息提升卫星影像定位精度进行了研究。以"像方直线上任意一点必然位于物方直线和投影中心所构成的平面"作为几何约束条件,通过对直线的参数化表示,建立了基于直线特征的共面模型;在该模型基础上,针对航天传感器的成像特点,分析建立了8标定参数的内方位元素模型和简化的外方位元素模型,最终构建了直线特征约束的卫星影像自检校平差模型。利用资源3号(ZY-3)卫星获取的华盛顿地区数据对构建的平差模型进行实验验证。结果表明,该模型能够解决缺乏地面控制点地区影像定位精度差的问题,可达到与常规自检校平差相同量级的精度。     

直线特征约束的高分辨率卫星影像区域网平差方法

以"像方观测直线与像方预测直线必须重合"作为几何约束条件,以有理函数模型(RFM)作为高分辨率卫星影像的几何处理模型,提出了一种直线特征约束的高分辨率卫星影像区域网平差方法。本文方法仅需像方直线与物方直线相对应,无须像方直线上的像点与物方直线上的地面点一一对应。通过对圣迭戈试验区的两景IKONOS影像、斯波坎试验区的两景QuickBird影像和普罗旺斯试验区的两景SPOT-5影像进行试验,结果表明:本文方法可以充分利用直线特征作为控制条件,有效补偿RPC参数中的系统误差,获得的IKONOS、QuickBird和SPOT-5影像区域网平差的平面与高程精度均优于1个像素。     

An automatic mosaicking method for building facade texture mapping using a monocular close-range image sequence

This paper presents an automatic mosaicking method for generating building facade textures from a monocular close-range digital image sequence. The process begins with the computation of the camera parameters (except the coordinates of the projective center), which are determined by combining vanishing point geometry with constraints of a straight line bundle as well as prior information of parallel lines in object space. The raw images are later rectified for the purpose of eliminating their salient geometric distortion. Next, automatic retrieval of the relevant image segment is implemented using the detecting range variance by means of the histogram of projective differences between the corresponding points for each of the facades from the raw image sequence. A strip model of the least-squares adjustment, which is similar to the strip block adjustment in aerial triangulation, is employed to determine the spatial alignment of each of the image segments in order to generate the facade textures from the relevant image segments. Afterwards, the entire building facade texture is mosaicked by ortho-image generation. Two refining strategies are proposed to optimize the mosaic result. One is refining the mosaic region where corresponding points are difficult to match but plenty of horizontal lines are available, and the constraint of corresponding horizontal lines is introduced to implement this process. The other strategy is to refine the unsatisfactory mosaic region by densifying the corresponding points by means of the spatial alignment of the relevant image segment computed by the strip method. The experimental results indicate that this method is widely applicable and compares well with other reported approaches with regard to automation level and applicability, for uncalibrated images as well as images with large geometric distortions.     

半全局约束下的多基线立体影像MVLL匹配方法

多视铅垂线轨迹法（multi-view vertical line locus,MVLL）能够以物方地面铅垂线为几何约束,匹配获取物方空间点的最佳高程,是一种实用的多基线立体影像匹配方法。针对MVLL匹配方法中的物方空间点独立匹配、缺少整体性约束问题,将物方空间局部光滑特性应用至匹配过程,提出了一种半全局约束下的多基线立体影像MVLL匹配方法。首先,将物方空间点沿地面铅垂线上的准确高程搜索,等效至像方空间沿核线方向上的准确视差搜索;其次,采用MVLL匹配方法计算物方空间点在多张影像上的等效像方匹配测度;然后,采用半全局匹配法（semi-global matching, SGM）对匹配测度进行多路径聚合分析,得到物方空间局部光滑约束下的等效视差图;最后,将等效视差图转化为物方空间点匹配高程,并对多基线立体影像进行多分辨率匹配处理,实现整体最优条件下的MVLL匹配。采用多类型地形特征与局部区域影像进行匹配实验与对比分析,实验结果表明,所提方法能够对多类型地形特征的物方空间匹配测度进行优化,获取更加可靠的匹配结果,具有更高的影像匹配性能。     

From point-based to feature-based aerial triangulation

This paper is concerned with using linear features in aerial triangulation. Without loss of generality, the focus is on straight lines with the attempt to treat tie lines in the same fashion as tie points. The parameters of tie lines appear in the block adjustment like the tie points do. This requires a unique representation of lines in object space. We propose a four-parameter representation that also offers a meaningful stochastic interpretation of the line parameters. The proposed line representation lends itself to a parameterized form, allowing use of the collinearity model for expressing orientation and tie line parameters as a function of points measured on image lines. The paper describes in detail the derivation of the extended collinearity model and discusses the advantages of this new approach compared to the standard coplanarity model that is used in line photogrammetry. The intention of the paper is to make a contribution to feature-based aerial triangulation on the algorithmic level.     

一种无需控制信息的智能手机自检校方法

传统的相机检校方法受限于高精度的三维检校场或已知空间结构的检校模板，针对这个问题，在分析智能手机成像特征的基础上，提出一种无需控制信息的相机检校方法。该方法主要包括两个步骤:首先按3×3模式采集影像数据，选取基准影像，分别与其他影像进行相对定向以构建单元模型，通过比例系数进行模型连接后建立自由网模型，将所有摄站点、物方点坐标纳入到统一的基准影像坐标系中；然后以选择的基准影像为参考，并考虑附加参数模型，进行自检校光束法自由网平差，解算其余影像相对于基准影像的方位元素以及附加参数，从而完成相机的检校。实验结果表明，该检校方法是有效的，可显著提高测量的精度。     

A bundle adjustment approach with inner constraints for the scaled orthographic projection

Bundle adjustment is a method for simultaneously calculating both the interior and exterior orientation parameters of a set of images, and the object-space coordinates of the observed points. In the case of long focal length lenses and narrow field-of-view (FOV) imaging situations, collinearity based (perspective projection) algorithms may result in linear dependencies between parameters that cause solution instability. The use of a scaled orthographic projection model based on linear algebraic formulations was therefore adopted to reduce this risk. Using quaternions, a new mathematical model is derived that includes the partial derivatives as well as the inner constraint equations for a scaled orthographic bundle adjustment. The model was then tested using two image sets of a single, small vessel (about 6 m length) with a cube target of known dimensions at two distinct ranges; perspective solutions were also calculated for comparison. RMS residual errors of 0.74-0.78 pixels associated with the new method compare favorably to a residual error range of 0.59-0.74 pixels using a perspective bundle adjustment of the same target points. Relative precisions (as a ratio of target size) of between 1:1650 and 1:750 have been achieved at ranges of 375 m and 850 m, respectively, given comparisons with the known cube dimensions. A third image dataset consisting of a network of 16 images was solved with a 1:2200 relative precision showing the new method can successfully handle high redundancy. For the experiments that were conducted, the new method was found to produce less precise results than the perspective bundle solution for a FOV of 0.50-0.65° where the object fills 5-8% of the image. However, it was found to match the precision of the perspective model (with an uncalibrated camera) for a FOV of 0.20-0.30° where the object of interest fills only 1-2% of the full image.     

一种基于直线特征的影像外方位元素解算理论与方法

与点特征相比,影像上的线特征,特别是直线特征,具有识别相对容易、使用灵活等优点,因此对直线摄影测量的研究已成为目前摄影测量的一个重要研究方向。依据空间直线在航空影像上的投影仍然是直线,并结合共线条件方程,通过线性化,推导了基于直线特征计算像片外方位元素的误差方程;并且给出了计算过程。最后,通过实验验证了基于线特征计算像片外方位元素理论与方法的可行性和可靠性。同其他方法相比,该方法具有易于理解、便于计算、实用性强、易于实现影像自动外部定向等特点。     

同名点及高程平面约束的航空影像直线匹配算法

针对直线匹配的难点问题及匹配约束的有效性,提出了同名点及高程平面约束的航空影像直线匹配算法。该算法在边缘点匹配结果和直线提取结果的基础上,首先利用直线邻域内的同名点确定候选直线及直线投影平面的高程值,再结合物方和像方相似性约束确定同名直线;然后根据直线索引对"一配多"的匹配结果进行整合,并对结果中的多直线进行合并,得到"一对一"的同名直线;最后利用"像方-物方-像方"的映射模式确定同名直线的同名端点。论文选取典型纹理特征的航空影像进行直线匹配试验,结果表明,本文算法能获得可靠的直线匹配结果。     

粒子加速器中高精度丝线绝对位置测量技术研究

粒子加速器中采用振动线技术进行共架单元上多块磁铁的高精度预准直，需要将振动线代表的磁中心引出进行共架单元之间的相对准直。为了获取以振动线为代表的丝线高精度空间绝对位置，本文对采用近景摄影测量技术进行点、线位置求解的方法进行了研究。利用单相机多站位的方法进行拍摄，通过标定板提供的高精度控制点坐标，采用自标定光束法平差对相机进行标定，并提出将空间直线离散成空间2点进行直线整体精确求解。对标定板上由2点组成的模拟直线进行测量验证，并与标定板提供的理论值进行对比，结果显示空间直线位置获取精度优于5 μm。这表明了本文理论和方法的正确性，为进一步研究丝线高精度空间绝对位置测量打下了基础。     

Validation of geometric models for fisheye lenses

The paper focuses on the photogrammetric investigation of geometric models for different types of optical fisheye constructions (equidistant, equisolid-angle, sterographic and orthographic projection). These models were implemented and thoroughly tested in a spatial resection and a self-calibrating bundle adjustment. For this purpose, fisheye images were taken with a Nikkor 8 mm fisheye lens on a Kodak DSC 14n Pro digital camera in a hemispherical calibration room. Both, the spatial resection and the bundle adjustment resulted in a standard deviation of unit weight of 1/10 pixel with a suitable set of simultaneous calibration parameters introduced into the camera model. The camera-lens combination was treated with all of the four basic models mentioned above. Using the same set of additional lens distortion parameters, the differences between the models can largely be compensated, delivering almost the same precision parameters. The relative object space precision obtained from the bundle adjustment was ca. 1:10 000 of the object dimensions. This value can be considered as a very satisfying result, as fisheye images generally have a lower geometric resolution as a consequence of their large field of view and also have a inferior imaging quality in comparison to most central perspective lenses.     

Orientation of MOMS-02/D2 and MOMS-2P/PRIRODA imagery

This paper deals with the orientation of three-line imagery which has been taken during the MOMS-02/D2 experiment in spring 1993, and during the MOMS-2P/PRIRODA mission since April 1996. The reconstruction of the image orientation is based on a combined adjustment of the complete image, ground control, orbit and attitude information. The combined adjustment makes use of the orientation point approach or the orbital constraints approach. In the second case, the bundle adjustment algorithm is supplemented by a rigorous dynamical modeling of the spacecraft motion. The results of the combined adjustment using MOMS-02/D2 imagery and control information of orbit #75b are presented. Based on the orientation point approach an empirical height accuracy of up to 4 m (0.3 pixel) is obtained. In planimetry the empirical accuracy is limited to about 10 m (0.7 pixel), since the ground control points (GCP) and check points could not be identified in the imagery with the required accuracy. Computer simulations on MOMS-2P/PRIRODA image orientation based on realistic input information have shown that good accuracies of the estimated exterior orientation parameters and object point coordinates can be obtained either with a single strip and a few precise GCP or even without ground control information, if a block of several overlapping and crossing strips with high geometric strength (q≈60%) is adjusted.     

GPS/IMU辅助机载三线阵影像光束法平差

建立了GPS/IMU观测值与外方位元素之间的数学关系,引入线性多项式、分段多项式和定向片内插3种数学模型用于机载三线阵影像的单航带及区域网光束法平差。ADS40数据的试验结果表明,在少量控制点的支持下,3种数学模型的单航带平差均可取得优于1.1个像素的定位精度,其中定向片内插模型最适合用于三线阵影像的空中三角测量。区域网平差的结果进一步证明,四角布设平高控制点即可得到最优的平差结果。     

城区机载LiDAR数据与航空影像的自动配准

为解决机载LiDAR数据与航空影像集成应用中二者的配准问题,提出了一种机载LiDAR数据与航空影像配准的方法。首先,直接在LiDAR点云中提取建筑物3维轮廓线,通过将轮廓线规则化得到由两条相互垂直的直线段组成的建筑物角特征,并在航空影像上提取直线特征;然后,根据影像初始外方位元素将建筑物角特征投影到航空影像上,并采用一定的相似性测度在影像上寻找同名的影像角特征;最后,将角特征的角点当作控制点,利用传统的摄影测量光束法区域网平差解求影像新的外方位元素。解算过程中采用循环迭代策略。本方法的主要特点是,直接从LiDAR点云中提取线特征,避免了常规方法从距离图(或强度图)中提取线特征所产生的内插误差。通过与现有基于点云强度图的配准方法的对比实验表明,在低精度初始外方位元素的辅助下,本文方法能够达到较高的配准精度。     

基于单位四元数的机载三线阵影像光束法平差

为克服欧拉角在空间方位的描述和插值中的局限性,采用单位四元数来描述相机的姿态,推导了四元数描述的共线条件方程。在此基础上,提出了将四元数球面线性插值(Slerp)引入到三线阵影像定向片法平差的思想,通过利用Slerp公式进行相机姿态的匀速插值,建立了基于单位四元数的三线阵影像平差的数学模型并进行了线性化。两套ADS40数据的试验结果表明,在区域四角布设平高控制点的情况下,基于Slerp模型的定向片光束法平差在平面和高程方向均可取得优于1个地面像元(GSD)的定位精度,是三线阵相机检校和空中三角测量较理想的技术手段。     

利用已有像控点的多期航空影像光束法区域网联合平差

为了充分利用已有航空影像与控制成果,节约作业成本,缩短作业周期,提出一种利用已有像控点联合多期航空影像进行整体平差加密的数学模型,并采用我国南方某地区的数据资料进行了试验证明。结果表明,联合平差能将已有像控点的控制作用通过多期影像间的同名点传递到最新航空影像上,联合平差加密点的平面精度与常规光束法区域网平差加密精度基本一致,而高程精度则取决于多期影像间同名点的观测值个数,同名点观测值越多,加密点高程精度越高,因此只要多期影像间存在足够多的同名点观测值,则联合平差的加密精度完全能够满足摄影测量地形图测绘的生产需要。     

城区铅垂线辅助空中三角测量研究

根据灭点理论建立了铅垂线辅助空中三角测量理论模型，讨论了控制点的分布和旁向重叠度对附加铅垂线约束的空中三角测量的精度与可靠性的影响，最后结合实际数据对上述铅垂线辅助空中三角测量理论分析结果进行了试验验证。试验结果表明，铅垂线约束可以作为一种控制条件，引入城区航空影像的空中三角测量，以减少传统空三所需的高程控制点数，为城区航空影像的空中三角测量解算提供了一种新的思路。     

高分辨率光学遥感卫星在轨几何定标现状与展望

光学遥感卫星影像在轨几何定标是确保影像几何质量的必要环节。首先介绍了光学卫星在轨几何定标方法的研究现状;然后,对于当前主流的基于地面几何检校场的在轨几何定标方法,结合光学卫星地面分辨率不断提高的发展趋势,阐述了其受限于对参考影像的依赖而存在的问题;最后,论述了无需地面定标场的在轨自主几何定标的发展趋势,并提出了多种基于多角度交叉约束成像的在轨自主几何定标方法构想。     

轨道约束的资源三号标准景影像区域网平差

考虑到同轨道拍摄的长条带卫星影像具有相同的误差分布特性,针对资源三号的标准景影像产品,提出了基于轨道约束的卫星影像区域网平差方法。首先,根据同轨相邻影像的偏移量计算轨道影像坐标系下的像点坐标;其次,通过同轨每景影像的RFM重新生成轨道影像的RFM,同时生成补偿格网;然后,根据基于像方仿射变换的RFM对轨道影像进行区域网平差;最后,利用求得的轨道影像的仿射变换参数重新计算原始单景影像的仿射变换参数。利用不同地区资源三号测绘卫星影像数据的试验表明,基于轨道约束的卫星影像区域网平差（以下简称轨道平差）在稀疏控制条件下,其精度明显好于单景影像平差的精度。在6控情况下,太行山试验区达到平面2.504m高程3.117m,在渭南试验区达到了平面4.061m高程2.895m。试验结果证明了轨道平差的有效性和可行性。