ALBERT

Notes: 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.

Notes: Detailed understanding of the processes which control river bank erosion requires high resolution information concerning temporal changes in bank morphology. This paper describes the successful use of digital photogrammetry to extract high resolution digital elevation models (DEMs) from terrestrial oblique stereopairs of rapidly eroding river banks, using the commercial software package Erdas Imagine. This software was developed for use with aerial photography and satellite imagery; problems relating to the use of oblique terrestrial images are discussed and solutions presented. Photography was acquired using semi-metric cameras, mounted on tripods and positioned about 15m from the eroding bank. Data for DEM point spacings of 20mm were obtained, with accuracies of approximately ±12mm in depth. Digital photogrammetry can permit faster analysis, provide better accuracies and involve less ground disturbance than conventional methods of monitoring river channel change. Most importantly, DEM generation is considered to be more useful than traditionally acquired points or profiles for landform monitoring strategies.

Notes: The design and performance of a computer assisted system for aerial triangulation, mapping and digital data output are described with examples of practical applications. The economic and human considerations are reviewed after three years' experience with the system in production.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméOn décrit le plan et le fonctionnement d'un système d'ordinateur assisté pour la triangulation aérienne, le rendement des données digitales et cartographiques, avec exemples de leurs applications pratiques. On explore les considérations économiques et humaines après 3 ans d'expérience avec le système en production.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungAuf bau und Leistungsfähigkeit eines rechnergestützten Systems zur Aerotriangulation, Kartenherstellung und digitalen Datenausgabe werden unter Angabe von Beispielen zur praktischen Anwendung beschrieben. Nach dreijähriger Produktionserfahrung wird ein Überblick über ökonomische und menschliche Probleme gegeben.

Notes: This paper considers a few aspects of the influence which Professor E. H. Thompson had upon the development of analytical techniques in photogrammetry, a field in which he was a prolific leader. The writer gives a purely personal view of Thompson's influence on his own studies, mainly in analytical aerial triangulation, over the period of their association.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméCette communication considère quelques aspects de l'influence qu'eut le professeur E. H. Thompson sur le developpement des techniques analytiques en photogrammétrie, un domaine dans lequel il fut un leader proliphique. L'auteur donne une vue purement personnelle de l'influence de Thompson sur ses propres études, en particulier sur la triangulation aérienne analytique, au cours de leur association.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungIm Beitrag werden einige wenige Gesichtspunkte bezüglich des Einflusses, den Prof. E. H. Thompson auf die Entwicklung analytischer Verfahren in der Photogrammetrie ausübte, einem Gebiet auf dent er eine herausragende Persönlichkeit war, erörtert. Dabei wird eine rein persönliche Ansicht bezüglich des Einflusses von Thompson auf die Arbeiten des Autors wiedergegeben, insbesondere in der analytischen Aerotriangulation während der Zeit, wo sie gemeinsam gearbeitet haben.

Notes: This article provides a brief description of the functions and capabilities of an image generating system developed by Linotype-Paul Limited for the Royal Aircraft Establishment, Farnborough.〈section xml:id="abs1-2"〉〈title type="main"〉Résumé Cet article donne une courte description des fonctions et des possibilités d'un système generateur d'images developpé par Linotype-Paul Limited pour Royal Aircraft Establishment, Farnborough.〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Kurze Beschreibung der Funktionen und Fähigkeiten eines bilderzeugenden Systems, das bei der Linotype-Paul Limited für das Royal Aircraft Establishment in Farnborough entwickelt wurde.

Notes: Problems are sometimes encountered during the relative orientation of close range photography which has a limited usable format and a large Z range. Computer simulations and practical tests with both a comparator and a plotting instrument are used to investigate the problems and possible inaccuracies. Systematic errors in the photogrammetric model are revealed.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméOn rencontre souvent des difficultés lorsqu'on forme un modèle avec des clichés pris à courte distance, à format réduit et lorsque l'objet présente quelque profondeur. On a approfondi ces problèmes en utilisant conjointement simulations et essais pratiques; on a prouvé ainsi que les déformations du modèle étaient systématiques.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungMitunter ergeben sich bei der relativen Orientierung von Nahbereischsbildern Probleme, weil das nutzbare Bildformat klein und der z-Bereich gross sind. Mit Hilfe von Computer-Simulationen und praktischer Tests mit einem Komparator bzw. einem Auswertegerät wurden die Probleme und mögliche Ungenauigkeiten untersucht. Dabei wurden systematische Fehler in dem photogrammetrischen Modell aufgedeckt.

Notes: Three investigations of the suitability of photogrammetry as a method of measurement are described, in the fields of marine, mechanical and structural engineering. Analytical solutions for a single model, a strip and a block of photographs are discussed.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméOn décrit trois tentatives de recours à la photogrammétrie en métrologie industrielle, dans les industries de la marine, de la mécanique, et des structures métalliques. On discute l'intérêt des solutions analytiques pour le couple, la bande ou le bloc de photos.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungBeschreibung von drei Untersuchungen bezüglich Eignung der Photogrammetrie als Messverfahren im Schiffbau, im Maschinenbau und im Bauwesen. Diskussion analytischer Lösungen für das Einzelmodell, die Bildreihe und den Block.

Notes: The concept of optimum interpolation is briefly explained. The use of polynomial and non-polynomial stepwise regression for obtaining optimum or near optimum interpolation is illustrated. Least squares collocation is presented as an advanced method for optimising stepwise regression whenever the latter does not achieve desired optimum interpolation for given terrain. A Fortran IV program, written to illustrate an optimum interpolation algorithm using stepwise regression and collocation, is found to produce better results than existing interpolation methods. Other applications of such an algorithm are also discussed.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméOn expose brièvement le concept d'interpolation optimale, ainsi que les méthodes d'approximation polynomials ou autres qui permettent de la réaliser localement au mieux. On présente la collocation comme une méthode permettant de parachever l'interpolation; on a trouvé effectivement, avec un programme écrit en Fortran IV, que les résultats obtenus ainsi étaient meilleurs. On envisage aussi d'autre types d'applications de cet algorithme.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungKurze Erläuterung des Begriffs der optimalen Interpolation. Skizzierung der Anwendung von schrittweiser Regression mit Hilfe von Polynomen oder anderen Verfahren zur Ermittlung optimaler oder genähert optimaler Inter-polationen. Die Kollokation nach kleinsten Quadraten wird als verbesserte Methode zur Optimierung der schrittweisen Regression dargestellt, wenngleich letztere keine optimale Interpolation für ein gegebenes Gelände liefert. Ein Rechenprogramm in Fortran IV, das zur Veranschaulichung eines optimalen Interpolations-Algorithmus mit Hilfe der schrittweisen Regression und Kollokation geschrieben wurde, lieferte bessere Ergebnisse als vorhandene Interpolationsmethoden. Andere Anwendungen eines solchen Algorithmus werden ebenfalls erörtert.

Notes: A panel of speakers, knowledgeable in the problems of photogrammetry in the Third World, led a discussion which considered the place of sophisticated photogrammetric equipment in the Third World, problems of technician and management training, the desire for self reliance, and the needs of map revision.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméUne confrontation entre photogrammètres sur le sujet photogrammétrie et tiers-monde; équipement, instruction des techniciens, problèmes d'organisation, désir d'autonomie, révision des cartes.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungEin Forum von Kennern der Probleme der Dritten Welt führte eine Diskussion über den Platz moderner Geräteausrüstungen in diesen Ländern, über Probleme der Ausbildung von Technikern und Führungskadern und erörterte den Wunsch nach Selbstbestätigung und die Notwendigkeit zur Laufendhaltung von Karten.

Notes: The problems associated with the depiction of a particular irrigation area by both line map and orthophotomap are described and the results compared.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméDes problèmes soulevés par la description d'une aire d'irrigation à l'aide d'une carte ou d'une ortho-photocarte: comparaison des résultats.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungBeschreibung der Probleme, die bei Auswahl sines Bewässerungsgebietes an Hand von Strich- und Orthophotokarten auftraten und Vergleich der Ergebnisse.

Notes: In 1981, a metric camera will be launched into space on a European Space Agency Spacelab mission. This paper examines the specification for this mission and the expected results. Other developments are also considered. These include the American large format camera and long focal length imaging systems.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméEn 1981, une chambre métrique sera lancée dans l'espace (mission Spacelab de l'organisation européenne spatiale). On examine ici les buts et les résultats attendus, ainsi que de futurs développements; chambre américaine à grand format, systèmes à longues focales.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungIm Jahre 1981 soll sich an Bord des Europäischen Spacelab-Satelliten eine Messkammer befinden. Im Artikel werden die Anforderungen an dieses Projekt und die zu erwartenden Ergebnisse diskutiert. Desgleichen werden auch andere Entwicklungen, worunter sich die amerikanische Grossformat-Kammer und langbrennweitige Systeme befinden, erörtert.

Notes: A close range photogrammetric system, developed around a 35 mm Pentax camera fitted with a wide angle lens (f = 21 mm) and an early Zeiss wide angle multiplex, has proved useful for both instruction and research. Student exercises involve all phases of photogrammetry, from establishing ground control to plotting, and permit the integration of useful statistical routines for data analysis. Research applications have centred on the topographic mapping of microscale landforms at scales of 1: 1 to 1: 10 with accuracies of ± 1 mm to ± 5 mm.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméUn système mis au point pour la photogrammétrie à courte distance, et dont les éléments essentiels sont une chambre Pentax (f = 21 mm) et un Zeiss grand angle multiplex, a fait la preuve de son utilité tant pour l'instruction que pour la recherche. Les exercices proposés aux étudiants comportent toutes les phases réelles, depuis l'établissement d'un canevas d'appui jusqu'à la restitution. Les applications à la recherche sont centrées sur la cartographie des microreliefs à des échelles variant de 1: 1 à 1: 10 avec des exactitudes variant de ± 1 mm à± 5 mm.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungEin Aufnahme- und Auswertesystem zur Nahphotogrammetrie, bestehend aus einer 35 mm Pentax Kamera, die mit einem Weitwinkelobjektiv (f= 21 mm) ausgerüstet war, und ein alter Weitwinkel-Multiplex von Zeiss haben sich bei der Ausbildung und Forschung als nützlich erwiesen. Bei den studentischen Übungen werden alle Phasen der Auswertung von der Passpunktbestimmung im Gelände bis zur Stereokartierung erfasst, wobei es auch möglich ist, statistische Tests zur Datenanalyse einzubeziehen. Die Forschungsarbeiten konzentrierten sich auf die Herstellung topographischer Karten von kleinmassstäbigen Geländeformen in den Massstäben 1: 1 bis 1: 10 mit Genauigkeiten von ± 1 mm bis ± 5 mm.

Notes: Stimulated by promising overseas results with colour aerial photography and encouraged by its potential for solving local problems, the Forests Commission, Victoria, embarked on a series of trials with colour photography in 1965. Early results showed great promise and resulted in further work. This paper describes the methods and results of 70 mm and 35 mm trials concerned with the evaluation of various photographic films. An important aim of the study was to build up a working knowledge of the techniques of using aerial films other than conventional panchromatic black and white and to assess their value under Australian conditions.〈section xml:id="abs1-2"〉〈title type="main"〉Résumé Stimulés par les résultats obtenus outre-mer en matière de photo aérienne en couleur, et disposant d'un potentiel adéquat, le Forests Commission, Victoria a entrepris en 1965 une série d'essais, dès le départ très encourageants. On décrit ici les essais d'évaluation de différents types de film (70 mm et 35 mm); le but était de se familiariser avec la couleur et d'en étudier les conditions d'emploi sous les latitudes australiennes.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungAngeregt durch erfolgversprechende Ergebnisse mit Farbluftbildern in Übersee und ermutigt durch die Möglichkeiten zur Lösung lokaler Probleme unternahm die Forstkommission in Viktoria (Australien) eine Reihe von Versuchen mit Farbaufnahmen im Jahre 1965. Diese Versuche erwiesen sich vielversprechend und wurden fortgesetzt. Im Artikel werden die Verfahren und Ergebnisse von Versuchen mit 70 mm und 35 mm Aufnahmen zur Bewertung verschiedener photographischer Materialien beschrieben. Ein wichtiges Ziel der Untersuchung war das Erlangen von Kenntnissen über die Verfahren zur Verwendung nichtkonventioneller panchromatischer Schwarz-Weiss-Filme und deren Bewertung unter australischen Bedingungen.

Notes: Professor F. Ackermann was specially invited to contribute an article to mark the 50th issue of The Photogrammetric Record. As the only photogrammetrist to have received both the Brock and von Gruber awards of the International Society for Photogrammetry, he is particularly well qualified to express his views on the past and future development of photogrammetry.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméLe professeur Ackermann a été invitéàécrire un article pour fêter la sortie du 50ème numéro. Seul photogrammètre cumulant médaille de Brock et médaille de von Gruber, il était particulièrement qualifié pour juger du passé et préjuger de l'avenir de la photogrammétrie.〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Professor Ackermann wurde gezielt eingeladen, um einen Beitrag anlässlich des Erscheinens der 50. Ausgabe des Photogrammetric Record beizusteuern. Als einziger Photogrammeter, der sowohl den Brock- als auch v. Gruber-Preis der ISP erhalten hat, ist er besonders qualifiziert, seine Ansichten über Vergangenheit und Zukunft der Photogrammetrie zu äussern.

Notes: In 1976 the author succeeded the late Professor E. H. Thompson as editor of The Photogrammetric Record, having been assistant editor since 1965. Here he sets out, on the occasion of its 50th issue, some of the details which fashion the content and appearance of the Record.〈section xml:id="abs1-2"〉〈title type="main"〉Résumé En 1976 l'auteur devient, après feu le professeur Thompson, rédacteur en chef du Photogrammetric Record; il était son adjoint depuis 1965. A l'occasion du 50eme numéro, il expose les conceptions qui président au contenu et à l'aspect de la revue.〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Im Jahre 1976 wurde der Autor Nachfolger von Professor E. H. Thompson als Redakteur der Zeitschrift Photogrammetric Record, nachdem er schon seit 1965 als stellvertretender Herausgeber tätig war. Anlässlich des Erscheinens des 50. Heftes beleuchtet er einige Einzelheiten, die Inhalt und Aufmachung des Record formen.

Notes: Antarctica, with its vast areas of snow, presents unusual problems to the photogrammetrist and the cartographer. The paper describes two methods used by the Directorate of Overseas Surveys to overcome these problems and to produce 1: 250 000 scale mapping. The first part of the paper gives an account of the use which was made of tricamera photography, with particular emphasis on the adaptation of Williamson multiplex equipment to operate with the oblique elements of tricamera photography. The second part of the paper, after outlining some of the fundamental principles of ERTS 1 (Landsat) imagery, goes on to describe the application of these principles when utilising imagery in the production of much needed image and line maps of Antarctic areas. Accuracies achieved by the two methods and their relative economies are discussed.〈section xml:id="abs1-2"〉〈title type="main"〉Résumé L'Antarctique, avec ses vastes étendues de neige, pose des problèmes particuliers au photogrammètre et au cartographe. On décrit ici deux méthodes utilisées par le Directorate of Overseas Surveys pour produire la carte au 1: 250 000. La première consiste à employer pour la prise de vues une chambre triple, associée pour la restitution à un multiplex Williamson modifié pour I'exploitation des vues obliques. La deuxième consiste en une tentative d'utilisation des images satellitaires ERTS 1 (Landsat). On analyse Vexactitude et le prix de revient des deux méthodes.〈section xml:id="abs1-3"〉〈title type="main"〉Zusammenfassung Die Antarktis bietet dem Photogrammeter und Kartographen mit ihren riesigen Schneeflächen ungewöhnliche Probleme. Im Artikel werden 2 vom Directorate of Overseas Surveys angewandte Verfahren beschrieben, um diese Schwierigkeiten zu überwinden und Karten im Massstab 1: 250 000 herzustellen. Im 1. Teil der Arbeit wird über die Anwendung von Dreikammer-Aufnahmen berichtet, wobei insbesondere auf die Adaption des Williamson-Multiplexgerätes zur Auswertung der dabei mit aufgenommenen Schrägbilder eingegangen wird. Im 2. Teil des Artikels werden die grundlegenden Prinzipien der ERTS (Landsat)-Aufnahmen skizziert und deren Anwendung zur Herstellung der dringend benötigten Bild- und Linienkarten antarktischer Gebiete beschrieben. Die mit den beiden Verfahren erzielten Genauigkeiten und ihre relative Wirtschaftlichkeit werden diskutiert.

Notes: The author has been involved in the manufacture of photogrammetric instruments for nearly 30 years. In particular, he was associated with the Thompson-Watts plotter and, at the present time, is concerned with the production of the CP1 and EMPD instruments which owe a great deal to his design and innovatory skills. This paper summarises his experiences and views of the production of photogrammetric equipment in England.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméPendant 30 ans l'auteur a participéà l'élaboration d'appareillages pour la photogrammétrie: en particulier les restituteurs Thompson–Watts; et maintenant les appareils CP1 et EMPD qui lui doivent beaucoup. Il condense ici l'expérience et les idées qu'il a dans ce domaine.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungDer Autor ist seit fast 30 Jahren an der Herstellung photogrammetrischer Auswertegeräte beteiligt. Insbesondere verbunden war er mit dem Thompson–Watts Plotter und befasst sich gegenwärtig mit der Fertigung der Geräte CP1 und EMPD, an denen er durch seine schöpferischen Fähigkeiten grossen Anteil hat. In dem Artikel werden seine Erfahrungen und Ansichten bei der Produktion photogrammetrischer Geräte in England zusammengefasst.

Notes: The author is one of the members of the International Committee for Architectural Photogrammetry (CIPA) which met in London during European Architectural Heritage Year. He describes architectural applications of photogrammetry in Poland.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméL'auteur est membre du Comité International de Photogrammétrie Architecturale (C/PA) réuni à Londres à l'occasion de l'Année du Patrimoine Architectural Européen. Il donne des exemples d'applications de la photogrammétrie à l'architecture en Pologne.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungDer Autor ist eines der Mitglieder des Internationalen Komitees für Architekturphotogrammetrie (CIPA), das während des Europäischen Jahres für Denkmalpflege in London tagte. Er beschreibt Anwendungen der Photogrammetrie in der Architektur in Polen.

Notes: Le microscope électronique à balayage donne l'image de la surface d'un objet situé dans une boîte à spécimen où a été fait le vide. Un fin pinceau d'électrons balaie la surface synchroniquement avec un tube cathodique dont l'intensité est modulée en fonction du signal secondaire émanant du spécimen. Le système présente une grande profondeur de champ; on peut donc obtenir différentes perspectives du spécimen en le photographiant sous diverses inclinaisons (perspectives qui sont centrales, mais cependant justiciables d'être traitées comme parallèles pour de forts grandissements) et donc le restituer spatialement. On donne dans la première partie les limitations pratiques de l'appareillage, ainsi que le type et les causes de distorsion de l'image. Dans la deuxième partie, on décrit les caractéristiques d'un appareil de restitution adaptéà un cas standard: grandissement des deux clichés d'un stéréogramme: fixe-angle d'ouverture du faisceau perspectif négligeable (c'est le cas pour de forte grossissements) et convergence relative des deux positions de la plaque porte-spécimen est fixe.〈section xml:id="abs1-2"〉〈title type="main"〉Zusammenfassung Das Abtast-Elektronen-Mikroskop liefert Bilder der Oberfläche von Objekten, die sich in einer Vakuum-Kammer befinden. Ein feiner Elektronenstrahl tastet die Oberfläche in Synchronisation mit einer Kathodenstrahlröhre ab, deren Lichtpunkthelligkeit von dem sekundären Elektronensignal, das von der Probe ausgeht, moduliert wird. Das System gestattet eine grosse Schärfentiefe und erlaubt dadurch verschiedene Projektionen des zu photo-graphierenden Musters durch Neigung desselben zwischen aufeinanderfolgenden Aufnahmen. Aus der Kenntnis der Geometrie der Projektion (die eine Zentralprojektion ist, jedoch für sehr stark vergrösserte Bilder annähernd als Parallel- oder Orthogonalfall behandelt werden kann) ist es daher möglich, zu dreidimensionalen Analysen durch Messung von Parallaxen zu kommen. Teil I der Arbeit handelt von den praktischen Problemen, die sowohl aus den Grenzen für die mechanische Konstruktion von Muster-Halterungen und Auswertegeräten als auch den Verzerrungen der Bilder resultieren. Teil II beschäftigt sich mit praktischen Gesichtspunkten der bewährten Auswerteinstrumente, die speziell für die Lösung eines standard-isierten Problems der Elektronenmikroskopie konstruiert wurden. Bei diesen wird die Vergrösserung der beiden Halbbilder eines Stereobildpaars konstant gehalten, der Divergenzwinkel der peripheren “Strahlen”, die sich aus dem zentralen “Strahl” ergeben, wird als vernachlässigbar angesehen (was bei Bildern mit starker Vergrösserung der Fall ist) und die Neigungswinkeldifferenz zwischen den zwei Lagen der Probe ist konstant.

Notes: The article describes an experiment in which a production block of aerial triangulation, observed by the method of independent models, was repeatedly computed using differing amounts and configurations of control. The block was recomputed to investigate the effects of control errors, of dispensing with the tie strips and of applying different weights to control and tie points. The connexion between the quality of the join of individual models and that of the adjusted block was also investigated.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméOn décrit une série d'essais effectués sur un bloc de production de triangulation aérienne analytique traité par la méthode des modèles indépendants, destinés àétudier l'influence du nombre et de la configuration des points du canevas d'appui, l'effet d'erreurs sur les points d'appui, l'effet des bandes transversales, et du choix des poids pour les points d'appui et de liaison. On a aussi examiné la corrélation entre la qualityé de l'enchaînement des modèles individuels et celle du bloc compensé.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungBeschreibung eines Versuchs, bei dem ein Aerotriangulationsblock aus der Produktion, der nach der Methode der unabhängigen Bildpaare beobachtet worden war, wiederholt bei verschiedenen Anzahlen und Anordnungen von Passpunkten berechnet wurde. Die Berechnungen erfolgten zur Abschätzung der Einflüsse von Passpunktfehlern. Weiter wurde der Anschluss zu Nachbarstreifen und die Anwendung verschiedener Gewichte für Pass- und Verbindungspunkte untersucht. Desgleichen wurde der Zusammenhang zwischen der Qualität des Zusammenschlusses einzelner Modelle und der des ausgeglichenen Blockes untersucht.

Notes: A plot of relative parallax measurements in a student exercise is proposed for revealing errors in parallax bar readings taken from a stereo-pair of aerial photographs. The sensitivity of the computed heights to measurement error is also evaluated.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméOn propose un tracé graphique des mesures de parallaxe pour mettre en évidence des erreurs de lecture à la barre de parallaxe.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungEs wird eine Auswertung relativer Parallaxenmessungen bei einer studentischen Übung vorgeschlagen, um Fehler der an einem Stereomikrometer vorgenommenen Ablesungen aufzudecken, die an Hand eines Luftbildpaars erfolgten. Der Einfluss des Messfehiers auf den Höhenfehler wird ebenfalls abgeschätzt.

Notes: This paper briefly examines the current position in absolute and exterior orientation and highlights some of the limitations of existing techniques. An alternative system for performing absolute orientation and, potentially, exterior orientation is introduced. Some preliminary tests have given encouraging results.

Notes: The aim of this study is to assess the impact of sensor size and resolution of different digital camera sensors upon the accuracy and precision of three dimensional data derived by photogrammetry. Kodak DC40, DCS420 and DCS460 digital cameras were used to produce digital images of retroreflective targets in a 4 m three dimensional test field. The image locations of the targeted points were automatically measured using an off the shelf image processing software package. Two different sub-pixel measurement approaches were examined: centre of gravity and weighted mean. From the automated sub-pixel measurement of the targeted points, results indicate that the high resolution DCS460 camera produces optimum results using either the weighted mean or centre of gravity approaches. Although this was perhaps expected, the far lower resolution DC40 camera performed better than was originally anticipated, suggesting potential for the cheaper DC40 for many applications.

Notes: This paper describes initial work carried out to advance the use of vision metrology and three dimensional visualization techniques in structural testing and monitoring. A description is given of a methodology for semi-automatically generating dynamic three dimensional computer graphics models, which is employed to provide a three dimensional spatial framework for conventional engineering instrumentation. The use of techniques developed for two structural measurement applications is explained and opportunities for current and future research are reported.

Notes: This paper investigates possible solutions to the problem of urban orthophotography. Extensive work has been carried out to attain the best possible results, using all the existing software in the Department of Geomatic Engineering, University College London. Two of the most promising methods, which yield the best results, are analysed further. New routines were written in C language, as additions to the existing software, to allow for the special problems that arise in urban areas. The final results overcome the problem of double mapping (or occlusions) and will potentially enable even greater success to be achieved. A simple accuracy assessment of the results has been made. Difficulties and current limitations are analysed and presented.

Notes: This paper describes the use of photogrammetry to measure and quantify ice accretion on an aerofoil section. A series of stereoscopic photographs was taken during the ice accretion on the section in an icing tunnel. From measurements made on these photographs with a Kern (Leica) DSR 14 analytical photogrammetric plotter, a series of three dimensional models of the ice surfaces was constructed. The results of the project are discussed and possible improvements in the methodology are suggested.

Notes: A theoretical model for describing a direct image to ground relationship for slant range images extracted from synthetic aperture radar imaging satellites (for instance ERS-1 and ERS-2) is formulated. The rigorous orbital model is based on orbital parameters. Transformations and equations describing the relationship are derived.

Notes: For in excess of 100 years, photogrammetry has played a significant role in documenting the cultural heritage of nations and peoples. Many recent advances in the technique have enhanced the use of photogrammetry as a recording tool, enabling more complex representations of objects and moving access to the procedure from the expert to the interested user. Some of these recent developments include low cost digital photogrammetric systems, image sequence analysis, bundle adjustment and camera calibration procedures, and three dimensional laser scanning. An overview of some of these developments is given in this paper.The University of Melbourne, in conjunction with Chulalongkorn University in Bangkok, has been working on a project to create a computer visualization of the ancient Thai city of Ayutthaya. This project has blended three dimensional CAD models of the architectural features of Ayutthaya with historical research and artistic rendering to build a realistic representation of this city as it may have existed in the past.The model of the city has been built up from historical “maps”, aerial photographs, field survey and the use of photogrammetry to derive models of individual wat, chedi, prang (see GLOSSARY) and statuary. The historical research conducted in Thailand has provided the basis for the determination of the most likely location and appearance of the missing structures. The CAD models created from the photogrammetry have been visualized by the addition of surface textures and materials and rendered in as realistic a manner as possible. The virtual city has also been augmented by the incorporation of live actors in the computer reconstruction.When completed, the end product will be capable of producing an experience of daily life in Ayutthaya, with the potential for giving the user a level of interaction. The reconstruction will also be used as the basis of a variety of educational products to be produced in Thailand on a number of different media, including a bilingual CD-ROM already developed to “proof-of-concept” stage.

Notes: 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.

Notes: This paper discusses the role of Ordnance Survey International as a division within Ordnance Survey and outlines the work currently being carried out world-wide. It identifies the commercial structure of the business and justifies the reasons for participation in overseas markets. The key business activities of Adviser to the United Kingdom Department for International Development, international relations, library services, training and consultancy are all described. In addition, three case studies are included to support the main text.

Notes: Some exciting developments have been made recently, in the field of digital image rectification, which are of interest to both the photogrammetric specialist and non-specialist. This paper outlines the technical processes involved in generating digitally rectified images, as well as raising some of the issues that are becoming apparent when applying this modern technology to archaeological and architectural presentation.

Notes: The number of people involved in the actual process of airborne data collection has always been relatively small in comparison with the large number of end users of the product. As with many aspects of photogrammetry, the techniques and equipment used in aerial imagery acquisition have changed rapidly over recent years. Other outside influences are having an effect on how aerial operations are carried out and this paper examines how these factors will affect air survey as we approach the millennium.

Notes: Book review in this ArticlePHYSICAL MEASUREMENTS AND SIGNATURES IN REMOTE SENSING. Edited by G. Guyot and T. Phulpin. A. A. Balkema, Rotterdam, 1997. ISBN 90 5410 917 3. Two volumes, each 172.254 mm. Volume 1: xiii + 390 pages; volume 2: x + 411 pages. Price NLG 225.MANUAL OF REMOTE SENSING, THIRD EDITION, VOLUME 2. PRINCIPLES AND APPLICATIONS OF IMAGING RADAR. Edited by F. M. Henderson and A. J. Lewis. John Wiley & Sons, Inc., New York, in co-operation with the American Society for Photogrammetry and Remote Sensing, 1998. ISBN 0 471 29406 3. 221.287 mm. xxv + 899 pages. 76 colour plates. Price US$198 hardback.GEOGRAPHICAL INFORMATION SYSTEMS. PRINCIPLES, TECHNIQUES, APPLICATIONS AND MANAGEMENT. Second edition. Edited by P. A. Longley, M. F. Goodchild, D. J. Maguire and D. W. Rhind. John Wiley & Sons, Chichester, 1999. ISBN 0471 32182 6 hardback. Boxed set of two volumes. 200.270 mm. Volume 1: xcv + 580 pages, with 40 colour plates. Volume 2: xciii + 521 pages, with 66 colour plates. Price £195.FUTURE TRENDS IN REMOTE SENSING. Edited by P. GUDMANDSEN. A. A. Balkema, Rotterdam, 1998. ISBN 90 5410 933 5. 180.254mm. xii + 496 pages, including 18 pages of colour plates. Price NLG 205.INTERPRETATION OF AIRPHOTOS AND REMOTELY SENSED IMAGERY. By R. H. Arnold. Prentice-Hall, Inc., New Jersey, USA, 1997. ISBN 0 02 303924 8. 225.274 mm. xiv + 250 pages. 189 figures, including 17 in colour. Price £21.95 spiral bound.GEOCOMPUTATION: A PRIMER. Edited by P. A. Longley, S. M. Brooks, R. McDonnell and W. MacMillan. John Wiley & Sons Ltd., Chichester, 1998. ISBN 0 471 98575 9 clothbound, 0 471 98576 7 paperback. 168.244 mm. xii + 278 pages, plus 8 pages of colour plates. Price £22.50 paperback.DIRECTORY OF AERIAL PHOTOGRAPHIC COLLECTIONS IN THE UNITED KINGDOM. Second edition. National Association of Aerial Photographic Libraries (NAPLIB), Dereham, 1999. ISBN 0 9530436 1 4. 210.297 mm. 132 pages. 8 plates and 3 figures. Price £40 (£20 to new members of NAPLIB and to members of the Photogrammetric Society).DIGITAL LANDSCAPE MODEL FOR EUROPE (DLME). By E. Blau, F. Boochs and B.-S. Schulz, with editorial assistance of P. R. T. Newby. OEEPE Official Publication No. 34. Institut für Angewandte Geodäsie, Frankfurt am Main, 1997. ISSN 0257 0505. 175.245 mm. 108 pages. 21 figures, 9 tables, 4 diagrams and 15 appendices. Price DM 40.THE AGI SOURCE BOOK FOR GEOGRAPHIC INFORMATION SYSTEMS 1998/99. Edited by C. Corbin. Association for Geographic Information, London, 1998. ISBN 1 847059 314. 210.297 mm. 396 pages. 43 trade directories and 21 reference tables. Price £39.50 paperback.

Notes: This paper discusses the application of two fixed base non-metric camera systems. The first is a helicopter supported 5m boom carrying two 70 mm Hasselblad cameras, fired simultaneously. The 1;850 scale stereomodels, each covering about 40 ×45 m, were used to measure individual tree characteristics, such as crown closure and size. The second system is a portable camera platform designed for microtopography, which used sequential Minolta 35mm photography (1;80 scale) for generating DEMs and computing volume of soil erosion. In both cases, an analytical plotter was used to collect measurements without ground control. With the helicopter boom system, distances and heights were measured to within 5 per cent of true dimensions. With the portable platform system, volume estimates were within 1 per cent of field measurement values. Particular attention is given to the orientation and scaling of stereopairs. Because the air base is used to scale the model, errors in scale due to non-parallel lines of sight are avoided. Advantages and disadvantages of both systems are discussed.

Notes: 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.

Notes: For the construction of the new Athens International Airport, it was imperative that a hill, obstructing air traffic, be lowered by approximately 40 m. Unfortunately, a fortified prehistoric settlement was situated on top of that hill. In order to carry out this task, it was required: (a) to produce a model of the site at a scale of 1;50; and (b) to monitor and document every single stone during the dismantling of the most important parts of the site, so that its rebuilding elsewhere and at a later time would be possible.The Laboratory of Photogrammetry, National Technical University of Athens, undertook to provide the necessary metric data. By using low altitude aerial photographs from a helicopter, a specialized tripod and terrestrial photogrammetric techniques, the following products were created, all at a scale of 1;50: contour lines and DTM of the site; digital orthophotograph of the site; graphic drawing of the development of the exterior of the surrounding wall; and graphic drawings of the upper (initial) and the lower (last) levels of the parts to be removed. In this paper, both the fieldwork and the final products are presented and evaluated.

Notes: The Department of Geomatics and the Regional Centre for Innovation in Engineering Design in the University of Newcastle upon Tyne collaborated in a project to produce precise measurements for use in the fabrication of the body of the “Angel of the North” sculpture. This 20 m high edifice, by the sculptor Antony Gormley, is located adjacent to the A1(M) in Gateshead, Tyne and Wear.This paper reviews the photogrammetric reverse engineering work carried out on a 1:10 scale plaster maquette of the “Angel of the North”, which is a life-size model of the sculptor's body without any arms. The three dimensional measurements of the maquette, made by analytical photogrammetric techniques, were then processed to produce a fully functional three dimensional CAD model from which the dimensions needed by the fabricating company, Hartlepool Steel Fabrications Ltd., could be extracted. Additionally, the VirtuoZo digital photogrammetric software package was used to investigate the potential of automated measurement for this type of work and the results were compared with those obtained analytically.

Notes: Although well established, digital photogrammetry continues to change. More sources offer imagery which can be treated photogrammetrically. Users need improved scanner performance as they attempt to offset costs by feeding clusters of workstations or establishing bureau services; increased speed, variable pixel size, use of roll film and “on the fly” dodging are desirable scanner characteristics. On the workstation side, the demand for the Windows NT platform has been irresistible. New applications and the quest for higher productivity have resulted in demands including output of orientation data to analytical plotters, processing of data from airborne GPS and inertial measurement unit (IMU), triangulated irregular network (TIN) DTMs, automated radiometric balancing in mosaicking, smoother operation within feature collection and batch processes. Moreover, the market place itself changes, with suppliers, their customers and the end users all competing for position.

Notes: The use of circular object targets is very common in spatial photogrammetric object reconstruction. An object circle is projected on to the image plane as an ellipse if the object plane and the image plane are not parallel to each other. The image co-ordinates of the centre of the ellipse are usually determined automatically by means of digital image processing. These co-ordinates are then used as observations for a subsequent reconstruction of the three dimensional object point. The image co-ordinates of the centre of the ellipse and the true co-ordinates of the projected centre of the circular object target are not identical; thus eccentricity is caused, resulting in systematic geometric image measurement errors. This paper describes the functional context of this eccentricity for a typical target/camera set-up. The possible solutions for a correction of this systematic eccentricity error are derived. Guidelines for the correct combination of object target sizes and exposure distances, guaranteeing reliable image point measurements and accurate object point determination, are proposed.

Notes: Dolphins are agile animals and are very difficult to measure at sea. However, for the conservation of threatened or endangered species, measurement may be vital because it allows a demographic analysis of the population. Hector's dolphin (Cephalorhynchus hectori) is a rare species living only in coastal waters around New Zealand where it is studied from small boats. This paper describes a stereophotogrammetric technique developed to measure body length accurately at sea without having to capture the individual. Constant calibration with the use of a control frame allowed accurate body length measurements of dolphins to be made with this low cost system, with a measurement error of 4 per cent to 6 per cent of actual length.

Notes: The users of many digital photogrammetric systems are allowed a degree of control over the automated digital elevation model (DEM) generation software with a set of strategy parameters. These parameters control the search and quality control characteristics of the algorithm; hence the wrong choice of parameters can have a significant detrimental effect on the accuracy of the DEM. This paper describes the strategy parameters used in the Erdas Imagine OrthoMAX digital photogrammetric system and a set of tests used to define the optimum set of parameters for a project. The algorithm employs an area correlator and a hierarchical approach in the matching process. The results show that a 35 per cent increase in accuracy can be achieved through the process of parameter optimization. They also demonstrate that changes to the strategy parameters have a similar effect on the results for all areas of a set of imagery used in the test, which is of particular note because the imagery contains a diverse range of landcover types. The paper additionally provides a description of a system currently being developed which will automatically prescribe the correct set of parameters for a project.

Notes: 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.

Notes: Book review in this ArticlePHOTOGRAMMETRY. Volume 2 Advanced methods and applications. By K. Kraus with contributions by J. Jensa and H. Kager. Fourth edition, translated into English by P. Stewardson.Dümmler Verlag, Bonn, 1997. ISBN 3 427 78694 3. 240 x164 mm. 466 pages. lllustrated. Price DM 88.ERROR PROPAGATION IN ENVIRONMENTAL MODELLING WITH GIS. By G. B. M. Heuvelink.Taylor & Francis, London, 1998. ISBN 0 7484 0743 X (hardback), 0 7484 0744 8 (paperback). 233 × 156 mm. xviii + 127 pages. Price £24.95 paperback.GOVERNMENTS AND GEOGRAPHIC INFORMATION. By I. Masser.Taylor & Francis Ltd., London, 1998. ISBN 07484 0789 8 (cased), ISBN 07484 0706 5 (paperback). 246 × 170 mm. xi + 120 pages. 10 figures, 6 colour plates and 10 tables. Price £19.95 paperback.AN INTRODUCTION TO GEOGRAPHICAL INFORMATION SYSTEMS. By I. Heywood, S. Cornelius and S. Carver.Addison Wesley Longman Ltd., Harlow, 1998. ISBN 0 582 08940 9. 245 × 187 mm. xiv + 279 pages. Black and white illustrations and colour plates. Price £18.99paperback.EUROPEAN GEOGRAPHIC INFORMATION INFRASTRUCTURES: OPPORTUNITIES AND PITFALLS. GISData series V. Edited by P. A. Burrough and I. Masser.European Science Foundation/Taylor & Francis Ltd., London, 1998. ISBN 0 7484 0755 3 (hardbac ISBN 0 7484 0756 1 (paperback). 252 × 173 mm. xv + 172 pages. 4 colour plates. Price £55–95 hardback, £26.95 paperback.INNOVATIONS IN GIS. Selected Papers from the Fifth National Conference on GIS Research UK (GISRUK). Edited by S. Carver.Taylor & Francis Ltd., London, 1998. ISBN 0 7484 0810 X. 252 × 174 mm. xxii + 246 pages. Numerous illustrations, including four colour plates. Price £69.95.SCALE IN REMOTE SENSING AND GIS. Edited by D. A. Quattrochi and M. F. Goodchild.Lewis Publishers, New York, 1997. ISBN 1 56670 104 X. 235 × 165 mm. 406 pages, 21 colour plates, including bibliographical references, index, many diagrams and illustrations. Price £48.00 hardback.PRACTICAL GEODESY: USING COMPUTERS. By M. Hooijberg.Springer-Verlag, Heidelberg, 1997. ISBN 3 540 61826 0. 273 x198 mm. xi + 308 pages. 69 figures and 21 tables. Price £49.00 hardback.GIS ONLINE: INFORMATION RETRIEVAL, MAPPING, AND THE INTERNET. By B. Plewe.OnWord Press, Santa Fe, New Mexico, 1997. ISBN 1 56690 137 5. 179 × 228 mm. xv + 311 pages. 99 figures. World Wide Web site containing supporting material and update information: Price £29.95 paperback.ANALYSIS OF SAR DATA OF THE POLAR OCEANS: RECENT ADVANCES. Edited by C. Tsatsoulis. and R. Kwok. Springer-Verlag, Berlin, 1998. ISBN 3 540 62802 9. 241 × 160 mm. vi + 290 pages. 125 figures, including 26 in colour, and 18 tables. Price £95.50 hardback.IMAGES OF THE EARTH: A GUIDE TO REMOTE SENSING. Second edition. By S. A. Drury.Oxford University Press, Oxford, 1998. ISBN 0 19 854997 0. 276 × 220 mm. viii + 203 pages. 201 illustrations, 2 tables. Price £25.00 paperback.EXPLORING GEOGRAPHIC INFORMATION SYSTEMS. By N. R. Chrisman.John Wiley & Sons, Inc., New York, 1997. ISBN 0 471 10842 1. 230 × 190 mm. xvi + 298 pages. 103 figures and 27 tables. Price £24.95 paperback.

Notes: Digital still cameras have been widely adopted for close range photogrammetry and machine vision applications. Due to the advantages of onboard storage of digital images, portability and rapid data processing, digital still cameras are rapidly becoming standard equipment for measurement tasks such as industrial metrology and heritage recording. As for any metric application, the accuracy of the derived object data is dependent, amongst many other factors, on the accuracy of the camera calibration. For the vast majority of photogrammetric applications, use of the simple case of a block invariant calibration model comprising the primary physical parameters, including the principal point position, is sufficient. However, cameras designed for photojournalism and domestic use, such as the Kodak DCS420 and 460 cameras, are well known for their calibration instability because the design is based on a 35 mm SLR camera body. In particular, previous research has shown that the principal point location is prone to movement during normal handling of the camera, due to the mounting mechanism of the CCD array. This paper reports on an investigation of the physical behaviour of the principal point location and compares different calibration parameter models for the Kodak DCS420 and DCS460 digital still cameras.

Notes: 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.

Notes: The University of Nottingham has been undertaking research into the dynamics of a golf club shaft during a swing for a number of years. The measurement of the deformation of the golf club as it is being swung has been undertaken by close range photogrammetry. The measurement system originally developed was based on the use of two 35 mm SLR cameras and the use of a direct linear transformation computation from measurements of the photographs made on a digitizing tablet. Recently, the system has been revised and enhanced, and the images are now scanned and measured digitally. This paper presents a background to the project, a description of the instrumentation and how it is used. The measurement and computational procedures are explained and results from trials will be discussed.

Notes: Imaging systems founded on current digital camera technology are finding widespread use in high precision measurement applications. A single digital CCD camera, or an array of such cameras, equipped with ring lighting equipment is commonly used to acquire imagery of high contrast retroreflective targets placed on the object at discrete locations to signalize points of interest. The precise and accurate measurement of each imaged target location is a fundamental requirement if suitable measurement tolerances are to be obtained. Whilst such systems are undoubtedly capable of producing excellent results, the practical effects of target image quality on the photogrammetric measurement process is in need of careful consideration. This paper revisits some fundamentals of the optical imaging of retrotargets and investigates some abilities of a range of digital camera systems to provide images of retrotargets that are appropriate to the measurement process. Some experimental results are presented including the imaging of planar arrays of differing sized retrotargets at differing angles and exposures and a series of network analyses in which the level of target image intensity has been varied systematically.

Notes: Stereotactic methods have been successfully used for the treatment of a wide range of neurological disorders. The main difficulties experienced with the current systems are their cumbersome frames and their time consuming positioning procedures. The South African Medical Research Council/University of Cape Town Biostereometrics Group, together with the Department of Neurosurgery of the University of Cape Town, in an attempt to overcome the problems associated with the present stereotactic guidance frames, have developed a very simple probe pointing device. The Cape Town Stereotactic Pointer (CTSP) is based on stereophotogrammetric principles but uses computed tomography as the imaging and measuring medium.

Notes: JET (Joint European Torus) Joint Undertaking is currently planning to install its new Gasbox Divertor remotely. In line with JET's policy and philosophy, it was decided to survey the divertor structure remotely to confirm its position, shape and integrity prior to installing the new tile configuration. A survey to metrology standards with sub-millimetre accuracy is required. While remote surveys have been carried out in the past, they have not been to this level of accuracy.Digital photogrammetry (the evolution of photogrammetry, using CCD cameras) in conjunction with “targetless” software was selected as being the most suitable technique. It was seen as the natural evolution of the survey techniques already developed for use at JET, as well as having the potential to assist in preparations for future remote handling operations. Photogrammetry requires a large number of retroreflective targets to ensure accurate results. Clearly it would not be practical to fit targets remotely to the divertor structure. However, a technique has been developed at JET which uses a combination of targeted and targetless photogrammetry. A number of frames fitted with targets will be remotely positioned on the divertor structure. When surveyed these targets allow accurate determination of camera positions. Specially developed software allows the selection of untargeted features of components in the digital pictures. Their co-ordinates can be determined by triangulation from the known camera positions. Trials have shown that accuracy of ±0.6 mm is achievable.This paper will describe the development of this concept, the design of the necessary equipment, the testing to prove the accuracy and feasibility and the trials carried out in JET's In-vessel Training Facility. These included remote handling of the six million pixel camera and other equipment, data handling and download via an ethernet link through the remote handling articulated boom, development of survey techniques, optimization of analysis techniques using coded targets for fast processing and finally the engineering assessment of the divertor structure based on survey results.

Notes: The importance of soil surface microrelief has been identified in the literature of soil erosion. However, studies of soil microrelief have often ignored photogrammetry as a means of obtaining soil surface data. This paper recognizes the validity of analytical photogrammetry to quantify height changes at the experimental plot scale (≤1 m2). Additionally, however, analytical photogrammetry enables the recording of non-morphological information (including soil aggregates and rock fragments) so that the impact of such features upon the evolution of soil surfaces may be considered. The two forms of information may then be integrated within a geographical information system to relate the effects of such features upon soil surface height changes.

Notes: The principal point has long been regarded as one of the fundamental parameters in camera calibration. In the age of film based aerial and large format terrestrial cameras, the principal point could be located by a variety of techniques with a certainty of ±10 mm (Carman and Brown, 1961) and this was considered sufficient. However, aerial cameras were precision, purpose built, expensive pieces of equipment where the assembly was painstaking and the location of the principal point measured to a known tolerance. In the digital era, photogrammetrists, and many others, are using cameras which have not been specifically designed or built for photogrammetry. For these cameras there is no requirement for the manufacturers to position the lens in a pre-defined location relative to the image sensing plane or for the lens manufacturer to align the lens elements precisely. In fact, deviations from the centre of the sensor can be a considerable percentage of the extent of the sensor (up to 10 per cent for some zoom lenses (Burner, 1995)). This paper discusses the development of methods of obtaining the location of the principal point, considers the relationship between the principal point and other parameters in the functional model, and shows how the location of this point can be estimated with and without recourse to autocollimation methods.

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: This paper presents a procedure for assessing the quality of a digital elevation model (DEM) which has been applied to the output of a normalized cross correlation based stereomatching algorithm. Using semimetric photography of natural gravel river bed surfaces acquired in the field, digital photogrammetry was used to extract DEMs automatically for use in characterizing surface roughness properties.The procedure for assessing DEM quality involves examination of (i) ortho-images, to provide a qualitative check on stereomatching performance; (ii) DEM collection statistics which quantify the percentage of correctly matched pixels as a function of those interpolated; and (iii) height differences between check points, measured using independent field survey, and corresponding DEM points. The concepts of precision, accuracy and reliability are defined in the context of DEM quality assessment and methods are outlined which can be used to assess these variables. The assessment is conducted for two adjacent stereopairs with similar characteristics, considering the effects of both DEM collection parameters and different lens models upon DEM quality.Results show that digital photogrammetry, in conjunction with independent field survey, can be used successfully for extracting high resolution, small scale DEMs from natural gravel surfaces. Components (i) and (ii) of the quality assessment suggest the need to optimize DEM collection parameters, although the effects of not using a properly specified lens model were minimal at this scale. Method (iii) showed that increasing stereomatching success does not necessarily lead to more accurately estimated DEM points. However, the use of method (iii) remained difficult because of the scale of the photogrammetric application being used; check point positioning within the photogrammetric co-ordinate system was only possible to ±10 mm which, for a gravel bed surface, was associated with elevation variance of a similar, sometimes greater, magnitude. The next stage of this research will require the use of higher quality check data, possibly from laser profiling.

Notes: The basic concepts and tools of automatic image registration are presented and the problems which exist are discussed. The paper describes work carried out at University College London on the registration of two images and on the registration of images with maps. It is shown that strategies have been developed which are applicable to different types of image and reference data and that with the tuning of well tried algorithms it is possible to achieve the required matching. The PAIRS technique for automatic registration of optical images from satellites has been implemented and tested and is now being developed for use with optical and microwave images. The ARCHANGEL system for registration of images with maps or vector data is also being implemented and initial results show considerable promise.