空间前方交会法测定像控点的精度分析

介绍了空间前方交会法测量像控点的方法及其平差理论;以焦作市电视塔为例,利用所测像控点的3维坐标进行了数据平差计算和精度分析,得出空间前方交会法方案的可行性结论.     

基于PRS的遥感图像地物信息提取模型

点源理论(PRS)是一种面向应用需求的集中信息处理方式。不同尺度、不同分辨率的点都是一定的综合信息场,是客观世界的真实反映。本文在数字图像处理过程中引入点源理论,探讨针对地物空间信息应用服务的遥感信息分析和处理模型,讨论基于点源的图像构造、知识构造及地物模型建造过程,给出基于点源的遥感图像地物提取流程。     

Bundle Adjustment with Self–Calibration Using Straight Lines

Increased use of digital imagery has facilitated the opportunity to use features, in addition to points, in photogrammetric applications. Straight lines are often present in object space, and prior research has focused on incorporating straight–line constraints into bundle adjustment for frame imagery. In the research reported in this paper, object–space straight lines are used in a bundle adjustment with self–calibration. The perspective projection of straight lines in the object space produces straight lines in the image space in the absence of distortions. Any deviations from straightness in the image space are attributed to various distortion sources, such as radial and decentric lens distortions. Before incorporating straight lines into a bundle adjustment with self–calibration, the representation and perspective transformation of straight lines between image space and object space should be addressed. In this investigation, images of straight lines are represented as a sequence of points along the image line. Also, two points along the object–space straight line are used to represent that line. The perspective relationship between image– and object–space lines is incorporated in a mathematical constraint. The underlying principle in this constraint is that the vector from the perspective centre to an image point on a straight–line feature lies on the plane defined by the perspective centre and the two object points defining the straight line. This constraint has been embedded in a software application for bundle adjustment with self–calibration that can incorporate point as well as straight–line features. Experiments with simulated and real data have proved the feasibility and the efficiency of the algorithm proposed.     

面向对象的空间数据模型设计方法

空间数据模型是GIS实现空间数据组织、表达、分析、处理和应用的基础。从面向对象的角度提出了面向对象空间数据模型（OOSDM）的相关定义、对象构建过程、空间数据组织和管理模式,并以城市道路交通信息为例,设计了道路交通信息的对象组织方法和构建过程。模型设计方法的研究为空间数据库的建设和数据共建共享提供了新的方法和思路。     

应用VB实现中线测量中任意点坐标的快速计算

根据带有缓和曲线的圆曲线的测设原理,应用了面向对象的VB语言,设计了曲线主点(五大桩)与细部点(各中桩)的坐标检核,实现了中线测量中任意点坐标的快速计算。     

基于激光扫描技术的变电站三维模型的建立

通过利用地面三维激光扫描仪获取的空间数据,进行惠泉变电站三维空间地物建模研究,建立三维仿真模型。通过研究发现,利用三维激光扫描技术可以快速建立三维空间的可视化模型,解决传统的测量仪器与测量方法在变电站等特殊领域的应用不足,为实现变电站资源、景观、安全、环境管理等社会资源的数字化、网络化及动态可视化,提供一个变电站的三维模型平台构建的新方向。     

不规则体体积计算三维激光点云切片法

体积参数是空间体对象形态分析的基本内容,难点是不规则体的体积计算。本文提出的点云"切片法",快捷准确地解决了由三维激光扫描空间体对象所得点云体的体积计算难题。该法先将三维激光扫描空间体对象所得点云按特定方向顺序进行等间距的切片处理,得到与点云体相对应的、离散的系列点云切片;再依切割次序逐一搜索点云切片外轮廓多边形,并计算多边形(即点云切片)的面积;最后,利用切片面积和相邻切片间距求解点云段块体积,并求和得到整体点云体(即所扫描空间体对象)的体积。算例计算结果与分析表明,基于切片的不规则体的三维激光扫描点云的体积计算方法正确、简洁、可靠、高效、可控,可以解决不规则体的体积计算问题。     

3DGIS中空间对象的存储与快速查询

空间对象的存储和快速查询是三维地理信息系统研究的基本问题。本文采用面向对象的方法将三维空间对象抽象为点、线、面、体四类,点对象用一个坐标点(x,y,z)来表示,线对象用一组首尾相接的线段表示,面对象与体对象用三角网表示,然后采用SQL Server 2005来组织存储数据。为了提高空间数据库的检索速度,作者编程实现了线性八叉树空间索引,应用程序采用目前比较流行的ADO.net技术来访问数据库。     

GIS中面向对象时空数据模型

由于当前的地理信息系统软件难以处理时态现象，时态数据模型已忧为ＧＩＳ领域的一个研究热点。许多学者提出了多种时态数据模型。本文作者在提出了矢量栅格一体化的面向对象数据模型之后，再一次对时态问题进行了分析研究，净面向对象的数据模型扩充到时间维。有三种方法表达空间对象的历史变化。第一种是将版本信息记录在关系表上；第二种是将版本信息标记在记录上；第三种是将版本信息标记在属性上。本文采用面向对象的方法，将版     

地物点测量精度的自评定方法研究

本文以地物特征点之间的几何条件建立条件方程,通过平差计算得到地物点测量的精度,由于不同于传统的地物点高精评定方法(对已测完的地物,再架设仪器测量特征点,用两次结果的差值评定地物点精度),故称为地物点测量精度的自评定法。其特点:一是通过平差计算可得到地物特征点测定中误差、地物面积的中误差和面积相对中误差;二是使基础地理数据有很好的几何上的一致性;三是绘图和精度同步,即当用平差后坐标绘图的同时,便知道其点位精度和面积精度。通过全站仪对直角楼房测量实验证明本文方法是可行的。     

3D reconstruction from a single image using geometric constraints

Photogrammetry has many advantages as a technique for the acquisition of three-dimensional models for virtual reality. But the traditional photogrammetric process to extract 3D geometry from multiple images is often considered too labour-intensive. In this paper a method is presented with which a polyhedral object model can be efficiently derived from measurements in a single image combined with geometric knowledge on the object. Man-made objects can often be described by a polyhedral model and usually many geometric constraints are valid. These constraints are inferred during image interpretation or may even be extracted automatically. In this paper different types of geometric constraints and their use for object reconstruction are discussed. Applying more constraints than needed for reconstruction will lead to redundancy and thereby to the need for an adjustment. The redundancy is the basis for reliability that is introduced by testing for possible measurement errors. The adjusted observations are used for object reconstruction in a separate step. Of course the model that is obtained from a single image will not be complete, for instance due to occlusion. An arbitrary number of models can be combined using similarity transformations based on the coordinates of common points. The information gathered allows for a bundle adjustment if highest accuracy is strived for. In virtual reality applications this is generally not the case, as quality is mainly determined by visual perception. A visual aspect of major importance is the photo-realistic texture mapped to the faces of the object. This texture is extracted from the same (single) image. In this paper the measurement process, the different types of constraints, their adjustment and the object model reconstruction are treated. A practical application of the proposed method is discussed in which a texture mapped model of a historic building is constructed and the repeatability of the method is assessed. The application shows the feasibility of the method and the potential of photogrammetry as an efficient tool for the production of 3D models for virtual reality applications.     

Excel环境下的条件平差可视化解算

在测量平差学习中,相当多的计算工作是矩阵转置、求逆、相乘等,人工解算繁复又容易出错。虽然有各种平差软件可以进行解算,但是一般过程均为隐含式的,不利于测量初学者掌握测量平差原理。本文利用Excel内置函数中的矩阵运算功能处理测量平差计算,并以高程控制网条件平差的解算为例,介绍其使用方法及技巧;不仅增加了测量平差原理可视化,而且使得平差计算更加简便和快捷,利于学生理解和吸收。     

面向对象的测量平差软件设计与网络化应用

对测量平差软件用面向对象的方法进行了重新设计，并用纯面向对象的Java语言实现了其抽象类和继承类，各种平差方法都以对象的形式出现，为程序代码的共享和多用户并发运行时字节码的共享打下了基础。     

Geocoding SAR interferograms by least squares adjustment

A geocoding model for Synthetic Aperture Radar (SAR) interferometry based on a least-squares adjustment combining interferometric phase, range, Doppler centroid frequency, flight path and control point data is proposed. The complete mathematical framework for the computation of object space coordinates without approximations is presented. It provides a way to an efficient implementation of the algorithm for geocoding the pixels of an interferogram. The method is preferably applicable to spaceborne dual-pass interferometry, and independent of the orbit configuration. An accuracy analysis of object point positioning is conducted and results of geocoding an ERS tandem interferogram are shown.     

不同型号GNSS在同一控制网中的兼容性分析

随着GNSS广泛应用于地籍测量和工程测量、大坝和大型建筑物变形检测以及地壳运动观测等领域。在布设控制网和施工过程中,往往存在同一型号仪器数量不足的问题。为解决这一问题,本文在同一控制网中使用不同型号的仪器同时作业,将不同接收机数据格式进行统一,并处理各种卫星信号,并进行联合基线解算、平差。研究结果表明:不同型号接收机在同一控制网中联合应用精度高于同一型号接收机在同一控制网中联合应用精度。     

空间物体分类及空间物体构造

空间物体描述是ＧＩＳ的基本任务之一，而空间物体的分类是空间物体描述的基础。理想的空间物体分类模型不但应具有完备描述（构造）各种空间物体的能力，而且应能够揭示基本的空间关系，有助于空间分析的规范化系统化。本文在分析空间概念模型和现有的几种空间物体分类模型的基础上，提出了空间物体分类的基本原则，给出了新的空间物体分类模型：简单点、复合点、简单线、有向简单线、复合线、有向复合线、多边形，并说明了以这类基本物体类型构造复杂物体的一般性方法。     

Tracking of facial deformations in multi-image sequences with elimination of rigid motion of the head

The paper deals with measurement of human facial deformations from synchronized image sequences taken with multiple calibrated cameras from different viewpoints. SIFT (Scale Invariant Feature Transform) keypoints are utilized as image feature points in the first place to determine spatial and temporal correspondences between images. If no temporal match is found for an image point by keypoint matching, then the tracking of the point is switched to least squares matching provided the point has one or more spatial corresponding points in the other views of the previous frame. For this purpose, a new method based on affine multi-image least squares matching is proposed where multiple spatial and temporal template images are simultaneously matched against each search image and part of the spatial template images also change during adjustment. A new method based on analyzing temporal changes in the image coordinates of the tracked points in multiple views is then presented for detecting the 3-D points which move only rigidly between consecutive frames. These points are used to eliminate the effect of rigid motion of the head and to obtain the changes in the 3-D points and in the corresponding image points due to pure deformation of the face. The methods are thoroughly tested with three multi-image sequences of four cameras including also quite large changes of facial deformations. The test results prove that the proposed affine multi-image least squares matching yields better results than another method using only fixed templates of the previous frame. The elimination of the effect of rigid motion works well and the points where the face is deforming can be correctly detected and the true deformation estimated. A method based on a novel adaptive threshold is also proposed for automated extraction and tracking of circular targets on a moving calibration object.     

Line segment confidence region-based string matching method for map conflation

In this paper, a method to detect corresponding point pairs between polygon object pairs with a string matching method based on a confidence region model of a line segment is proposed. The optimal point edit sequence to convert the contour of a target object into that of a reference object was found by the string matching method which minimizes its total error cost, and the corresponding point pairs were derived from the edit sequence. Because a significant amount of apparent positional discrepancies between corresponding objects are caused by spatial uncertainty and their confidence region models of line segments are therefore used in the above matching process, the proposed method obtained a high F-measure for finding matching pairs. We applied this method for built-up area polygon objects in a cadastral map and a topographical map. Regardless of their different mapping and representation rules and spatial uncertainties, the proposed method with a confidence level at 0.95 showed a matching result with an F-measure of 0.894.     

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.     

基于地物特征提取的车载激光点云数据分类方法

车载激光扫描测量方法较传统摄影测量方法具有更多优点,它能快速采集大面积、高精度的三维空间数据,具有广阔的应用前景。针对车载激光扫描数据的分类问题,提出了一种基于地物特征提取的点云数据分类方法,即采用主成分分析(PCA)方法,在提取多种街区地物点云数据几何特征和总结地物对象特征知识规则的基础上,根据选取的主特征设计一套阶层式的分类方法,并利用该方法对一套车载激光点云数据进行了分类试验。结果表明,该方法的分类效果良好,具有一定的实用性。