DIGITAL IMAGE CORRELATION: PERFORMANCE AND POTENTIAL APPLICATION IN PHOTOGRAMMETRY

A procedure for digital image correlation is described which is based on least squares window matching. The immediate aim is high precision parallax assessment, point transfer, and point measurement. Experiments and theory have confirmed the high accuracy potential of the method. By implementation of charge coupled device (CCD) video cameras in an analytical plotter, an experimental hardware and software configuration has been established with which the operational on line application of digital image correlation for conventional photogrammetric measuring tasks can be tested. First results of calibration and performance of the system are presented. They allow optimistic conclusions as to the further development and practical application of digital image processing in photogrammetry.     

Low Cost Digital Rectification on A PC

Digital photogrammetric techniques have opened fresh horizons and have enabled photogrammetry to become a more user friendly tool for a wide range of applications. However cost remains a critical issue, because new digital photogrammetric workstations and their related software are considered expensive. This paper examines the problem of digital rectification and presents low cost solutions involving the use of commercial off the shelf software packages, which include graphics and painting software, image processing tools and a CAD system. Additionally, specially developed software performing vector rectification is described and discussed. All the packages have been used for rectifying digital images and the results are presented. An attempt is also made to assess the accuracy and reliability of the results. Finally, several alternative digital products are presented, mainly concerning the use of the methods described in the restitution of cultural monuments.     

The Z/I Imaging Digital Camera System

Market needs for airborne and spaceborne imagery used in photogrammetry and GIS applications are changing. Fundamental changes in sensors, platforms and applications are currently taking place. Most recently, new high resolution spaceborne sensors have become available. Besides classical photogrammetry, new thematic applications will drive the future image market. Savings in cost and time, together with the need for higher and reproducible radiometric resolution or spectral information will push forward the change from analogue to digital imagery. High resolution satellites will compete with airborne film-based photography and digital camera systems.
With the availability of a digital airborne camera, it is possible to completely close the digital chain from image acquisition to exploitation and data distribution. The key decision regarding the camera design in this case is whether a linear or area array sensor should be used. In view of the high geometric accuracy requirements in photogrammetry, Z/I Imaging has focused development on a digital camera based on an area sensor. An essential aspect of this decision was not only the aerial camera system, but also the entire photogrammetric process to the finished photographic or mapping product. If this point of view is adopted, it becomes clear that the development of a digital camera involves more than simply exchanging film for silicon. Aspects such as data transfer rates, in-flight data processing and storage, image archiving, georeferencing, colour fusion, calibration and preprocessing have the same influence on the economic assessment of a digital camera system. This paper describes current development activities and application aspects of a digital modular airborne camera system.     

Digital Photogrammetry and Microscope Photographs

The feasibility of applying commercial digital photogrammetric software to the measurement of small objects photographed through an optical microscope has been examined. The objects, about 20 mm across, were photographed using a 35 mm film camera (at the lowest magnification setting of the Olympus microscope) giving photographs at a scale of 2:1. The photographs were then scanned before processing with the VirtuoZo digital photogrammetric system. Various problems needed to be overcome, some due to the limited options available with the highly automated digital system which was not designed for such measurement tasks. The unusual image scales, the uncommon pixel sizes and the unconventional and uncertain imaging geometry, all impeded immediate photogrammetric implementation. Photographic problems with the microscope were also faced, as with all microscope photogrammetry. Creating control points and independently assessing the accuracy of results at these scales were also difficult operations, but an analytical plotter was utilized for both these purposes and to verify the imaging geometry. Once such problems were overcome, image matching proceeded well and an accurate DTM could be created successfully, provided that a suitably textured object was chosen.     

Some Thoughts on the Emergence of Digital Close Range Photogrammetry

This presentation offers some thoughts on the emergence (that is essentially to say the commercial acceptance and exploitation) of close range digital photogrammetric systems. The discussion is restricted to systems based on standard photogrammetric processes involving digital frame imagery. Systems are classified into three tiers which are distinguished not only by accuracy and cost, but also by the degree to which a technology transfer has taken place from the specialist photogrammetrist to the non-specialist user. This technology transfer, it will be argued, has facilitated dramatic growth in the application of low accuracy, low cost three dimensional modelling systems in areas such as heritage recording, multimedia, process plant documentation and forensic photogrammetry. Along with automation, this technology transfer has also largely accounted for the wider use of high accuracy, high cost, off line and real time vision metrology systems in large scale industrial metrology. Rapid growth in these two system categories is then contrasted against the more modest advances being witnessed in the traditional close range photogrammetric service sector. Prospects for the future are also touched upon.     

基于ECR与ECI星历数据的遥感影像定位

经典的共线方程中物方坐标系建立在地球表面,在航天摄影测量中,地面摄影测量坐标系的应用,增加了不同类型测量数据间联合处理的难度,限制了影像数据摄影测量处理的空间范围。本文介绍了基于视线方向的影像对地定位算法原理,并以此为基础建立了地心系下的航天影像摄影测量共线方程。针对地固地心系和空固地心系下星历数据的不同点,建立了基于两种地心系下星历数据的航天遥感影像定位严密模型,并对两种模型中偏流角处理的不同点进行了分析,最后给出了一个应用试验。     

The `Digital Projector': Raytracing as a tool for digital close-range photogrammetry

In close-range applications, digital methods are increasingly used. In addition to the software and techniques which were adopted from aerial photogrammetry, new strategies for the restitution and presentation of digital data have been developed. The `Digital Projector' is a strictly photogrammetric approach using raytracing techniques and off-the-shelf software to provide 3D models with complete texture. It works regardless of the shape of the object while allowing digital presentation (`photomodels') with numerous derivative results (e.g., orthoimages and animations).     

BUILDING A DIGITAL CLOSE RANGE THREE DIMENSIONAL MEASURING SYSTEM FOR LESS THAN £5000

The use of CCD cameras for digital photogrammetry has only slowly been taken up by the photogrammetric community. However, the pace of change is quickening with better understanding and cheaper equipment. Recently a decision was made to start some research into close range three dimensional digital measurement. The overall objective was to develop a low cost system for the automated measurement of small industrial objects. This shorter contribution describes the initial stages of this work.     

Emergence of an Integrated Softcopy Stereoplotter System to Replace Analogue Stereoplotters

Stereoscopic softcopy photogrammetric systems were originally as expensive as analytical stereoplotters, which prohibited their use in most small production firms. At the lower end of the cost spectrum, the functioning of these systems has previously been somewhat limited. Advances in computing technology and software architecture have now made an economic replacement of analogue stereoplotters a reality. A reasonably priced, high performance, off the shelf production solution is now possible on standard PC hardware. This paper provides a comparison of analogue and digital photogrammetry for a production work flow, commencing after scanning the films and progressing through project set up, orientations, stereodisplay and feature collection, DTM collection and editing, finally ending prior to orthophotography production. The underlying breakthrough software architecture making an effective digital system possible at moderate cost is described in detail and the benefits of such a system compared with analogue plotters are highlighted.     

虚拟航空摄影测量实验系统的设计与实现

随着网络教学的兴起,虚拟现实技术用于实验教学,成为强化实验室建设、改革实验教学手段的一个重要发展方向。介绍虚拟建模和开发软件,并以我院仿真模拟摄影测量与遥感实验室为原型,采用VRML软件为主,三维建模软件SkecthUP和3Ds Max为辅,阐述系统设计与实现的具体过程,构建虚拟航空摄影测量实验系统。该系统主要包括虚拟地形地貌沙盘(虚拟校园模型和虚拟栅格地形)、虚拟全数字摄影测量工作站模型、虚拟无人机和控制轨道动态模型,以及虚拟实验室场景。具有数字摄影测量工作站动态操作演示、无人飞机航空摄影测量操作演示,以及实验室参观展示等功能。研究成果无实体实验室的时空限制,有利于学生开展自主学习,有效地提高摄影测量实验教学质量,其对于虚拟实验系统的研发具有一定的借鉴意义。     

Description and evaluation of the high quality photogrammetric scanner UltraScan 5000

Scanning of analogue images has become a key hardware technology specific to modern digital photogrammetry. Since specialised photogrammetric scanners have been introduced in the late 1980s, a gradual development and improvement of their performance regarding hardware, software and functionality, and productivity has been observed. Originally, geometric accuracy of scanners was the overriding specification for scanners. This is increasingly being augmented by a concern for good colour and radiometric performance. This article describes the UltraScan 5000, a modern photogrammetric scanner manufactured by Vexcel Imaging Austria, and its features, assesses its radiometric and geometric performance with various well-founded tests, and discusses its versatility and use in production. The UltraScan 5000 was introduced in November 1998 and since then, a surprisingly large number of systems has been installed worldwide. Their successful operation illustrates on a daily basis the validity of the technical solution and tests at user sites have confirmed a good to excellent performance regarding geometric accuracy and resolution, radiometric performance (noise, dynamic range) and colour rendition.     

Modelling and representation issues in automated feature extraction from aerial and satellite images

New digital systems for the processing of photogrammetric and remote sensing images have led to new approaches to information extraction for mapping and Geographic Information System (GIS) applications, with the expectation that data can become more readily available at a lower cost and with greater currency. Demands for mapping and GIS data are increasing as well for environmental assessment and monitoring. Hence, researchers from the fields of photogrammetry and remote sensing, as well as computer vision and artificial intelligence, are bringing together their particular skills for automating these tasks of information extraction. The paper will review some of the approaches used in knowledge representation and modelling for machine vision, and give examples of their applications in research for image understanding of aerial and satellite imagery.     

3D Reconstrution with Rational Function Model

Rational Function Model (RFM) is the alternate sensor Model to the rigorous sensor model that allows end user to perform sensor-independent photogrammetric processing. Nowadays, commercial off-the-shelf (COTS) digital photogrammetric work stations have incorporated RFM as a method for image restitution. It is technically applicable to all types of airborne and space borne sensors. In this paper, we describe the derivations of the algorithmic procedure for third order inverse and forward RFM method for 3-D reconstruction. Model accuracy is evaluated for aerial image, TK-350 Russian image and IRS-1C PAN image. The results ensure that properly constructed RFM are accurate enough to be used in place of the original rigorous models. The test results are reported and summarised.     

侧视雷达影像距离-共面模型严密定位

本文对现有侧视雷达遥感影像的几何构像模型在摄影测量应用中的不足进行了理论分析,以外方位元素作为定向参数,依次建立了像点坐标显函数形式的距离-共面(R-Cp)方程、地心直角坐标系中星载侧视雷达影像的距离-共面方程、以及星载侧视雷达遥感影像的严密定位模型,并进行了稀少控制点条件的星载TerraSAR-X影像定位试验。理论和试验表明,本文所建立的R-Cp严密定位模型,使得雷达影像像点量测坐标作为摄影测量观测值的属性得到体现,容易吸收和利用光学遥感影像基于共线方程模型发展起来的成熟的数字摄影测量数据处理方法,有利于提高雷达遥感影像摄影测量数据处理的严密性、稳定性、可靠性及数据处理效率。     

Effects of Jpeg Compression on the Accuracy of Digital Terrain Models Automatically Derived from Digital Aerial Images

It is well recognised that data volume represents a huge overhead for softcopy photogrammetry. For example, a file size of 100 Mbytes will be generated from a black and white aerial photograph if digitised with a resolution of 20μm. Large data volumes not only create storage problems but also affect the speed of image processing. As a consequence, data compression of image data is a matter of great significance. This paper describes an investigation into the effects of image compression on the accuracy of digital terrain models (DTMs) extracted from the compressed images. The JPEG system implemented in the Z/I Imaging ImageStation digital photogrammetric workstation (DPW) was used in the study. A systematic test has been carried out on the effect of different levels of JPEG compression (with Q-factors from 1 to 100) on the resulting DTM, which is automatically generated by the DPW using Match-T software. An analysis of the results from the two sites tested shows that image compression tends to cause more significant degradation when the image texture is richer, but that recommendations on Q-factors for use with the ImageStation appear to err on the side of caution. This analysis leads to some tentative conclusions and recommendations both for future investigation and for photogrammetric practice.     

The Role of a Digital Intelligent Camera in Automating Industrial Photogrammetry

In the past few years the automation of digital industrial photogrammetric systems has increased dramatically. Due to digital image processing software, coded targets and automatic matching methods, a huge number of photogrammetric measurement tasks can be fully automated. In many cases a "one button click" is enough to provide the three dimensional co-ordinates of measured points without any manual interaction, immediately after acquiring the images. The technology of intelligent cameras is a logical step towards automated photogrammetric measurements. An intelligent camera, which has an integrated computer, analyses the image immediately after it is taken. This technology provides not only a much shorter processing time for the images but also more control over the measurement process just when it is needed, during image acquisition. This takes place in the form of real time feedback.
This paper describes the role of a digital intelligent camera in the automation of an industrial photogrammetric measurement system and gives an overview of existing automation techniques in industrial photogrammetry. As an example of an intelligent camera, the performance of the new INCA digital intelligent camera, developed and manufactured by Geodetic Services, Inc. (GSI) and distributed by Leica, is described.     

Photogrammetric Solutions for Industrial Automation and Process Control

Digital photogrammetric systems have been introduced to solve various measurement problems in industrial applications for many years, ever since high resolution CCD cameras and powerful computer technologies have been available. For a successful implementation of a digital photogrammetric system into the production line, not only does the actual measurement task have to be solved but also a complete integration of the system into the production process usually has to be supplied by the system manufacturer. Three examples of successful implementations of photogrammetric systems for industrial automation and process control are presented in this paper.     

Pavement Deformation Monitoring in a Rolling Load Facility

This paper describes work undertaken to measure deformation of a pavement within the Newcastle University Rolling Load Facility (NUROLF). Precise three dimensional measurements of the pavement have been produced from stereo-imagery taken with diVerent cameras, using both analytical and digital photogrammetric instrumentation. The photogrammetric measurements, and those from the existing system consisting of an array of linear voltage displacement transducers, have been compared with measurements produced using a digital level. Encouraging results have been achieved and photogrammetry has been shown to be capable of producing a similar accuracy to the existing system. There are many advantages associated with a photogrammetric survey but attempts to establish a permanent, automated photogrammetric system for the rolling load facility at a reasonable cost have so far been unsuccessful. It is anticipated that, with the falling cost of high resolution digital sensors, such a system will soon be possible.     

谈大数据时代的“云控制”摄影测量

在当今大数据时代,影像数据采集方式的多样化、高效化、便捷化产生的摄影测量影像大数据需要高效、自动与智能的处理。然而,作为传统摄影测量几何定位主要控制数据的外业控制点,其获取的复杂性与低效性仍然是制约摄影测量处理效率的关键因素。针对该问题,本文提出了"云控制"摄影测量的概念,以带有地理空间信息的数据作为几何控制替代外业控制点,通过自动匹配(或配准)获取大量密集的控制信息;并介绍了基于影像、矢量和LiDAR点云的3种"云控制"摄影测量技术;最后对"云控制"摄影测量的应用前景进行了展望并对其问题进行了讨论。     

DMC数字航摄在大比例尺地形图成图中的应用

数字航空摄影具有从测量到成图的全过程数字化的优点。结合1∶2000地形图DMC全数字摄影测量项目对面阵CCD航摄像机用于大比例尺航测成图的基本要求进行了分析研究,提出数字像机的几何标定、数字摄影的质量检验和生产作业规范制订的必要性。