ALBERT

Notes: Hierarchical approaches for automated photogrammetric surface measurement invariably employ image pyramids and image matching at multiple resolutions. Such an approach is also applicable in industrial photogrammetry where projected light patterns are used to provide texture on an otherwise texture-free surface. This paper describes a novel strategy for hierarchical surface measurement in which projected non-repeating target patterns are employed, rather than the lower-resolution levels of an image pyramid. Thus, although the final derived digital surface model is obtained by image matching, preliminary surface models which support the matching are obtained using the non-repeating patterns. These projected patterns allow a simplification of the triangulation phase since they offer the potential of a fast and unambiguous solution to the image point correspondence problem. Following an introduction to the non-repeating pattern strategy, integration of the approach into a multi-camera vision metrology system is described and some experimental measurements are summarized

Notes: Informal settlements are a common feature of developing countries. In South Africa the improvement of living conditions in these settlements and the upgrading to formal housing types are regarded as being of central importance to the nation's development. Effective settlement improvement and upgrading activities, which we here term “management”, require adequate spatial data. To date, the acquisition of spatial models of informal settlements has been based on conventional mapping techniques, and mostly on photogrammetry. Data are compiled using analogue or analytical methods. These are manual and hence require both considerable expertise and expensive equipment. Moreover, these methods are uneconomical over the often relatively small, densely populated areas covered by informal settlements and are also too expensive to employ with a regularity required to support such tasks as change detection. Alternative imaging sources and mapping techniques are therefore needed.In this article we examine the problem of spatial information acquisition for informal settlement management from three perspectives: spatial information requirements, the role which imagery can play in satisfying these spatial information requirements, and effective imaging options. We focus on the potential of high resolution satellite imaging, small format digital aerial imagery and digital multispectral video systems for rapid mapping. We also discuss the example of automated shack extraction from aerial imagery.

Notes: The advantages of vision metrology (VM) systems over their film-based counterparts, in terms of the degree of automation within the measurement process, were initially confined to the image mensuration stage. Of late, however, the potential of significantly raising the level of automation of offline and real time VM systems has been more fully exploited, to the point where full automation of the offline procedure has been realized. Innovative features such as automatic image point identification via coded targets, exterior orientation through automatically recognizable “control” groupings of target points, determination of image point correspondences within unlabelled point clouds, and real time tracking of multipoint, handheld measurement probes are now incorporated in industrial VM systems. Another significant innovation is the development of “smart” cameras with incorporated image processing and measurement capabilities which remove the necessity for transmitting image data to the host computer. This paper reviews recent innovations in automation and discusses their operational impact on practical VM applications. The concepts discussed are illustrated through reference to a modern VM system which supports offline and real time measurement.

Notes: The recently released Nikon E2 still video camera incorporates reduction optics technology which enables a full conventional 35mm image to be recorded on a 2/3 inch (17mm) CCD array. This paper investigates the metric impact of reduction optics through application of the technique of multisensor system self-calibration. The influence of the JPEG image compression facility contained within the E2 is also assessed in an overall evaluation of the camera for vision metrology applications which demand relatively high object point triangulation accuracies.

Notes: This paper addresses aspects of relative observational weighting for GPS camera station positions, ground control and image co-ordinate data in GPS aerial triangulation. Weighting implications for different control point and drift parameter scenarios are discussed, a two stage adjustment/transformation procedure is proposed and the implications of observational weighting on triangulation precision are reviewed. Bundle block adjustment results from a 626 photograph, 1650 point GPS aerial triangulation project are presented to illustrate the outcomes of different weighting and ground control strategies.

Notes: Developments in automated close range photogrammetry over the past decade have produced systems capable of achieving measurement accuracies of one part in several hundred thousand of the size of the object. The impetus for precision photogrammetry has come mainly from the industrial sectors of aircraft, aerospace and antenna manufacturing, but potential applications are not limited to these areas alone. This paper discusses the applicability of industrial photogrammetric techniques for the monitoring of ground surface displacements which accompany oil recovery operations. A pilot study is reported in which photogrammetric positioning accuracies at the millimetre level were sought over an area of 1 × 1.6 km. The large scale of the convergent network, coupled with the high level of positioning accuracy, meant that special consideration had to be given to both operational aspects (helicopter photography and targeting) and mathematical modelling (refraction compensation). Lessons learned in this project have implications for the broader application of high precision photogrammetry in large scale civil and geotechnical engineering, as well as in the mining industry. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé Les progrès réalisés dans la photogrammétrie rapprochée automatisée au cours de la dernière décennie, ont débouché sur des systèmes capables ďeffectuer des mesures avec une précision de quelques cent millièmes de la taille de ľobjet. La photogrammétrie de haute précision a bénéficiéďune impulsion venant essentiellement du secteur des industries de ľaviation, de ľaerospatial et des constructeurs ďantennes, mais ses applications potentielles ne se limitent pas à ces seuls secteurs. On examine dans cet article la possibilityéďapplication des techniques de photogrammétrie industrielle à la surveillance des mouvements de la surface du sol qui se produisent dans les opérations ďextraction du pétrole. On décrit une opération-pilote dans laquelle on recherchait des précisions de localisation photogrammétrique de ľordre du millimètre sur une zone de 1 × 1,6km. La réalisation ďun réseau de photographies convergentes prises à grande échelle et destinées à fournir une précision de localisation de haut niveau, a demandé de prêter une attention particulière aux aspects opérationnels (photographie en hélicoptère et pré-balisage) ainsi qu'à la modélisation mathématique (corrections de réfraction). Ľexpérience acquise dans ce projet pourra être utilisée pour une application plus étendue de la photogrammétrie de haute précision dans le domaine du génie civil ou géo-technique à grande échelle ainsi que dans ľindustrie minière. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Entwicklungen in der automatisierten Nahbereichsphotogrammetrie haben in der letzten Dekade zu Sstemen geführt, mit denen Meβgenauigkeiten von 1 zu einigen Einhunderttausend der Objektgröβe möglich sind. Der Anstoβ zur Präzisionsphotogrammetrie kam hauptsdchlich von der Luftfahrt-, Raumfahrt- und Antennenindustrie, aber mögliche Anwendungen sind nicht darauf beschränkt. Im Artikel wird die Anwendbarkeit von Verfahren der Industriephotogrammetrie auf Bewegungen der Gelände-oberfläche, die im Zusammenhang mit der Förderung von Erdöl auftreten, diskutiert. Es wird über eine Pilotstudie berichtet, bei der man über ein Gebiet von 1x1,6 km photogrammetrische Positioniergenauigkeiten im Millimeter-Bereich anstrebte. Der groβe maβstab des konvergenten Netzes, gepaart mit dem hohen Niveau der Positioniergenauigkeit bedeuteten, daβ sowohl die operationellen Aspekte (Hubschrauberaufnahmen und Signalisierung) ah auch die mathematische Modellierung (Kompensation der Refraktion) spezielle Überlegungen erforderten. Die bei diesem Projekt gesammelten Erfahrungen haben einen Einfluβ auf die breitere Anwendung der Präzisions-photogrammetrie auf groβmaβstäbige Aufgaben im Bau- und Geo-ingenieurwesen sowie im Bergbau.

Notes: Photogrammetric measurements within environmental test chambers which incorporate viewing ports constitute an application of multi-media photogrammetry. Perturbations to the incident bundles of rays due to refraction must therefore be taken into account. In this paper, refraction compensation for the case of antenna measurements within thermal vacuum chambers is discussed. Correction models applicable to the camera invariant refracting surfaces of a glass window and vacuum chamber are reviewed, especially error compensation using the approach of analytical selfcalibration. Results of a sequence of measurements of a satellite antenna are then analysed to illustrate the high measurement accuracies which are afforded by the selfcalibration approach. 〈section xml:id="abs1-2"〉〈title type="main"〉Résumé Les déterminations photogrammétriques dans un environnement de caissons ď essais munis de hublots de visée, constituent une application de la photogrammetrie à trovers des milieux multiples. II y a lieu par conséquent de tenir compte des perturbations que subissent lesfaisceaux de rayons lumineux incidents par suite de la réfraction. On examine dans cet article la compensation de la réfraction dans le cas de mesures sur des antennes placées dans des enceintes thermiques sous vide. On analyse les modèles de correction applicables aux surfaces réfractantes invariantes de la chambre photographique et de ľ enceinte à vide, comprenant des fenêtres en verre, en s'attachant plus particulièrement à une compensation ď erreurs basée sur des méthodes ď auto-étalonnage analytique. On présente ensuite les résultats ď une série de mesures portant sur une antenne de satellite, qui illustrent le haut degré de précision atteint par cette méthode ďauto-étalonnage. 〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Photogrammetrische Messungen innerhalb von Umwelt-Testkammern, die auch Öffnungen zum Durchblick enthalten, stellen eine Anwendung der Multimedien-Photogrammetrie dar. Demzufolge müssen Störungen wegen Refraktion bei den Aufnahmestrahlenbündeln berücksichtigt werden. Im vorliegenden Beitrag wird die Kompensation der Refraktion für Antennenmessungen in thermalen Vakuum-Kammern diskutiert. Korrekturmodelle, die auf die kamerainvarianten brechenden Oberflächen eines Fensterglases und die Vakuum-Kammer angewandt werden können, werden analysiert, besonders unter dem Gesichtspunkt, daß eine Fehlerkorrektur mittels Selbstkalibrierung erfolgt. Dann werden Ergebnisse einer Folge von Messungen an der Satellitenantenne analysiert, um die hohe Meßgenauigkeit darzustellen, die aus dem Ansatz zur Selbstkalibrierung resultiert.

Notes: Over the past decade, photogrammetry has been increasingly applied as a precise three dimensional measuring tool in industrial and engineering works. Analytical photogrammetry is now routinely employed in tasks of measurement as diverse as machine tool inspection and fixture checking, structural deformation monitoring, the provision of control databases to guide industrial robots and the measurement of structures in earth orbit. Traditional photogrammetric techniques and instrumentation are usually inappropriate for industrial work and the development of complete, fully integrated close range photogrammetric systems has recently gained considerable impetus. This paper details some of the significant new developments in industrial photogrammetry, with particular reference to technological advances in the Simultaneous Triangulation and Resection System (STARS) designed by Geodetic Services, Inc. for industrial photograininetry. Practical aspects of industrial measurement are also presented in a review of some of the varying tasks that GSI has carried out in recent years. Emphasis is placed on demonstrating the flexibility, accuracy, reliability and economy of photogrammetry, as well as the progress made in automating this measurement technique.

Notes: The development of still video CCD cameras with digital image storage has made feasible the concept of offline, single sensor vision metrology. This paper reports on practical evaluations of such a system for dimensional inspection of aircraft tooling and for structural monitoring for large scale engineering. A further application of still video technology for low altitude aerial mapping is also reported. In each case a Kodak DCS200 camera has been employed for the photography in order to take advantage of the relatively high sensor resolution and adequate on-board image storage capacity. Aspects of the measurement operations, which yielded object space accuracies to 1:80 000 in the industrial measurement projects, are discussed and the results analysed.