ALBERT

Notes: A joint research project between the University of Newcastle upon Tyne and City University is developing a prototype system for using kinematic GPS techniques to derive the exterior orientation of an oblique sensor without the use of co-ordinated ground control. This paper presents an overview of the techniques employed in deriving GPS antenna co-ordinates and their subsequent use in finding the required orientations. The latest results and future plans are presented and discussed.

Notes: The paper entitled The Photogrammetric Society Analogue Instrument Project was published in The Photogrammetric Record, 14(82): 565-582 (October 1993) and contained, as Appendix A, an extract from the Archive concerned with the history of the Zeiss Stereoplanigraph in Great Britain. A further two extracts have since been published to provide details of direct optical projection instruments used in this country. This fourth extract now goes on to begin to provide some details of analogue plotters that employed a purely mechanical solution. The first instrument of this type to be described is the Vivian Thompson Stereo-plotter of 1907. It was in fact the very first instrument of this important category ever to be produced but unfortunately it was also the only one produced in Great Britain.

Notes: Civil engineering projects start with intensive site investigations to evaluate the appropriateness of the geographic location to the intended construction. This process is lengthy and crucial to the success or failure of the project. Personnel with multiple skills are required at the evaluation stage, including experts in soil mechanics, geology, surveying, management, structures and meteorology. However, many less fortunate parts of the world lack such expertise and cannot afford it. The main objective of the research described in this paper is to develop an expert system that will use images from different sources to assess sites for civil engineering works. Five engineering applications have been selected for this research. Certainty factors for uncertain or incomplete information are presented. A frame-based expert system is developed and tested in this research. Three different tests have indicated that the system is accurate and promising for site investigations.

Notes: This paper indicates the advantages afforded when an analytical plotter is interfaced with a three dimensional CAD system. Problems associated with combining various data sources (ground survey, aerial and close range photography) of differing quality will be discussed, together with compromises required to idealize the geometry of the real world enforced by a CAD system.The paper is illustrated by some of the commercial projects undertaken by the Engineering Photogrammetry Unit at City University. Applications of particular financial significance include modelling of petro-chemical plant for different purposes and to various levels of detail and accuracy

Notes: Over the past ten years, Photarc Surveys Limited has been taking aerial photography from a low flying helicopter to determine road surface spot heights. Developments in technology over this period have resulted in investigations into improvements in this technique and, in particular, in the provision of control for the photography. This paper represents the preliminary investigations into the problem of providing control for the photography including some experiences of using an inflight control system.

Notes: This paper outlines a series of tests undertaken to determine the repeatability of, and the distortions introduced in, the process of converting conventional images into digital form using Kodak Photo Compact Disk (Photo CD). Photo CD was introduced by Kodak in the early 1990s and, if proved to give stable, high quality images, could be a low cost, convenient alternative to other scanning systems. The images could then be used in photogrammetry for a variety of applications from simple cataloguing of images to data for digital systems to produce sub-pixel measurements.

Notes: Integrating Photogrammetric Techniques With Machine Vision And Scene Analysis II by I. J. Dowman, p.323Kodak Digital Cameras For Small Format Aerial Photography by R. W. Graham, p.325From Pixels To Sequences by S. Robson, p.327

Notes: Despite the potential of close range photogrammetry for high accuracy measurement, it has rarely been used by other than experienced photogrammetrists. One major contributing factor is the expertise needed to design multistation sensor configurations. This paper presents a conceptual model for the most fundamental task in this design problem, configuring a first approximation to a strong imaging geometry. This task entails making decisions on the number of camera stations needed and where they should be placed (positioned and oriented). The conceptual model is based on the theory of generic networks. A generic network constitutes compiled expertise, describing an ideal configuration of camera stations that can be employed to provide a strong imaging geometry for a class of network design problems. In addition to improving our understanding of cognition in network design, this model performs an important role in the development of an expert system for automated network design for dimensional inspection tasks.

Notes: The accuracy of subpixel target image location is an important factor that contributes to the overall precision of three dimensional measurement when using CCD cameras. This shorter contribution reports the effect of an electrical adjustment of a frame grabber that results in a significant and systematic error in the accuracy of target image location using some target location methods.

Notes: Books reviewed:R. Florek and C. Martin, Proceedings Of The Second Workshop On Surveying Education In Southern AfricaH. Burman and K. Torlegårc, Empirical Results Of GPS-Supported Block TriangulationA. Andreyevskiy, Directory Of Russian Space Industry 1994-1995M. Ware, Mechanisms Of Image Deterioration In Early Photographs: The Sensitivity To Light Of W. H. F. Talbot's Halide-Fixed Images 1834-1844.G. Lindig, Deutsches Fachwö Rterbuch. Photogrammetrie Und Fernerkundung (German Technical Dictionary. Photogrammetry And Remote Sensing)

Notes: Prospective customers often request information on the accuracy of digital photogrammetry. Suitable data have been scarce, so Leica has begun a programme of internal tests. These are neither comprehensive nor necessarily representative of other suppliers' equipment, but several experienced operators and sets of imagery are being used and the results do provide general guidelines. A selection of analogue, analytical and digital workstations is being tested, together with scanners giving different pixel sizes.The early stages of the work are reported here. The tests include interior and exterior orientation of individual stereomodels followed by measurement of check points. Subsequent stages, covering DTMs, orthophotographs, mosaics and aerial triangulation, are planned.

Notes: The use of a 35 mm or similar camera set up over a theodolite is described for surveying mountain and polar glaciers where conditions do not allow for extensive detailed surveying or the use of heavy phototheodolites. Though used initially by Spender and Wright in the 1930s on Mount Everest and in Greenland and Arctic Canada, but apparently not by others since then, it was again tried out by Wright in Iceland in 1992. Modern analytical techniques have shown that heights accurate to within 2 m can be obtained from these photographs at distances up to 5 km. In addition, five times as many points can be identified and intersected in the laboratory from the photographs as was possible using sketches in difficult field conditions. Some reasons are suggested for the lack of use of this technique by others. The potential of existing survey photographs taken in Arctic Canada for large scale surveys of high polar glaciers in 1938 is described, with the hope that glaciologists and photogrammetrists might undertake their analysis.

Notes: The goal of automated three dimensional measurement of arbitrary objects using photogrammetric methods is a long way from being achieved, but significant progress is being made. However, automated measurement of small objects using inexpensive CCD cameras and frame grabbers is becoming increasingly common. A number of such systems have been developed both for commercial use and for academic research. It is within this latter context that a system to measure objects within a controlled environment has been developed at City University. The objective of the research is not only to produce a flexible measuring system for use in online inspection, but also to address many of the fundamental problems that hinder three dimensional measurement outside a controlled environment.

Notes: An ERS-1 SAR image of Frankfurt was geocoded using a variety of DEM spatial resolutions to examine the influence on positional accuracy compared with control points derived from a 1:50 000 scale map of the same area. It was demonstrated that mapping to 1:50 000 scale was possible in flat areas with a DEM resolution finer than 200 m.The case for SAR imagery in nautical charting is discussed in the light of these results, drawing on recent experiences at the Hydrographic Office in charting the South Orkney Islands.

Notes: The AP190 analytical stereoplotter has been employed for two research projects concerned with the urban and suburban environment. In the first project, the suitability of the AP190 was assessed for comparing height readings between stereomodels of colour diapositives and colour paper prints, for collecting height data for a digital terrain model and for producing a land use map using a stereopair of part of Edinburgh under well controlled conditions. The second project dealt with the densification of minor control points by means of the BLOKK aerial triangulation package, followed by the digital mapping of a suburban area planned for land readjustment in Bangkok.

Notes: Book Reviewed:D. Shirvanian, European Space Directory 1994J. P. Snyder, Flattening The Earth. Two Thousand Years Of Map ProjectionsP. A. Henkel, T. W. Augustyn and W. G. Fishell, Airborne Reconnaissance xvii

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: 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.

Notes: Correction for image distortion in cameras has been an important topic for as long as users have wanted to faithfully reproduce or use observed information. Initially the main application was mapping. While this task continues today, other applications also require precise calibration of cameras, such as close range three dimensional measurement and many two dimensional measurement tasks. In the past, the cameras used were few in number and highly expensive whereas today a typical large industrial company will have many inexpensive cameras being used for highly important measurement tasks. Cameras are used more today than they ever were but the golden age of camera calibration for aerial mapping is now well in the past. This paper considers some of the key developments and attempts to put them into perspective. In particular the driving forces behind each improvement have been highlighted.

Notes: During a project concerned with DEM generation using SPOT stereoscopic imagery, difficulties were experienced when using Level 1B stereopairs for the task. This paper presents a mathematical solution to overcome this problem which has been implemented at the University of Glasgow. Results are included from experimental tests which were carried out over a test field in Jordan using this solution. These tests used five SPOT Level 1B stereopairs together with a single SPOT Level 1A stereopair for comparative purposes. The residual errors at the ground control points and independent check points are given and show that a satisfactory solution was achieved.

Notes: The calibration of phototheodolites such as the Wild P32/T2 combination sometimes involves determining not only the camera interior orientation parameters but also the camera-to-theodolite parameters. The latter become particularly important when the theodolite set orientation parameters are to be used as observations, especially as known quantities for data reduction in subsequent photogrammetric applications. This paper presents experiments to determine these parameters for a Wild P32 camera using a new camera-on-theodolite method, with details of results achieved.

Notes: The TopoSys laser scanner system is designed to produce digital elevation models (DEMs) at a maximum accuracy of 0.5 m in x and y and 0.1 m in z. The regular scan pattern and the measurement frequency of 80 000 measurements per second (on average 5 measurements per m2) form the basis for high quality DEMs.The mainly automated data processing makes it possible to generate DEMs of large areas in a short production time. The DEMs produced come into common use as basic data for different applications, some of which are water resources management, shoreline control, planning of utility lines and urban planning (simulation of noise and pollution distributions). The performance of the system is illustrated with the help of DEM sections produced with the TopoSys system.

Notes: This paper examines the recent emergence of integrated coastal zone management as an application for the gathering, management and distribution of geospatial data. The requirements of a geospatial database of the coastal zone are outlined and the contribution of digital photogrammetry is examined. A saltmarsh monitoring project, which uses digital photogrammetry and was initiated by the authors, is described

Notes: Methods for deformation monitoring are based on two-epoch analysis. During geometrical deformation detection, it is required to transform the results into a common datum, identify a set of stable points and localize the deformation. This paper describes a flexible analysis procedure that incorporates stability determination, congruency testing, S-transformations, localization and testing of spatial deformation. The procedure has been implemented into a computer program, DETECT. Two photogrammetric monitoring schemes were analysed using DETECT for identifying the significance of spatial deformation between epochs. The results confirmed the suitability of the procedure in practical applications.

Notes: The main activities carried out by Ordnance Survey Ireland are focused on the production and maintenance of both small and large scale topographic databases. In 1980, photogrammetric methods were extensively adopted to carry out these tasks, based on analytical procedures. A review of operating practices in 1992 led to the introduction of digital systems. The technical complexities of the installation of digital hardware and software in a production environment are reported in this paper. An expanded role for the photogrammetric department also required the acquisition of new skills by its personnel. Experience has shown that further development, based on co-operation between vendor and user, must continue in the digital field.

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: A photogrammetric plotting system based upon digitizing tablets, a personal computer and a CAD system is proposed. The system, which is capable of working stereoscopically with the aid of a mirror stereoscope, can perform inner, relative and absolute orientations, and functions like an image space plotter. Simultaneous plotting is achieved because the system runs from Autocad through a program written in Autolisp. In this way, all the CAD editing capabilities can be used and the final map can be transferred without problems into several well known geographic information systems. Applications in terrestrial photogrammetry are also possible. The accuracy depends directly on that of the digitizing tablets and it can be improved significantly with proper compensation of systematic deformations.

Notes: The paper entitled The Photogrammetric Society Analogue Instrument Project was published in The Photogrammetric Record 14(82): 565-582 (October 1993). Extracts have appeared in each subsequent issue such that all the standard types of analogue instruments mentioned in the catalogue have now been included, some 28 instruments in all.In this final extract, the three remaining instruments listed in the catalogue are dealt with. All are of a type usually known as approximate solution instruments because they did not attempt any form of accurate space intersection but relied on applying a number of corrections to a model formed on the assumption that the photographs being used were true verticals taken at the same altitude. The accuracies achieved by such instruments depended both on how close the photography being used was to this ideal situation and on the degree of sophistication in the design of the analogue correctors incorporated in any particular instrument. The raison d'être for such a genre of instrument was essentially one of cost. Any organization faced with the requirement to produce small scale topographic mapping of an extensive region within a reasonable period of time might consider spending its available funds on a larger number of cheaper approximate solution instruments, always provided that an acceptable degree of accuracy could be maintained. Fortunately for such projects the specification would normally be for mapping of a graphical order of accuracy produced from high altitude photography. At such altitudes, stable flying conditions and small camera tilts of the order of 3° to 4° could realistically be expected. However, to obtain the best possible results from such photography, the best images possible should be provided for the operator, a factor sometimes overlooked by some manufacturers in their attempts to produce cheaper instruments.In view of the background to the development of British photogrammetry mentioned in previous extracts, it is perhaps surprising that a successful instrument of this type was not produced in the UK at a much earlier point in the era of analogue photogrammetry. Approximate methods were certainly favoured and promoted but only as far as planimetric maps were concerned. For these, form lines rather than contours were drawn when height information was considered necessary. However, when it was finally produced, the Thompson CP1 (manufactured by Cartographic Engineering Ltd.) proved to be an excellent instrument of its type and less approximate in its solution than most of its competitors. The other two instruments described in this extract are the Zeiss Stereotope and the Galileo-Santoni Stereomicrometer. The instruments are introduced in the order of their appearance on the market, which is also the order of the degree of sophistication found in the analogue computers they employed to reduce the errors introduced by any camera and airbase tilt present in the photography.

Notes: In this paper, different ways of performing large scale mapping of built up areas are discussed. Emphasis is placed on large scale representation through digital orthophotographs as the visualization medium of the real world. In an application, the process of creating perspective views of an orthophotograph draped on the digital terrain model of the study area is described; these views include the blocks of the built environment as three dimensional objects. The cartographic product is derived from a pair of overlapping aerial photographs processed through photogrammetric and GIS software packages. Finally, the perspective view of the digital orthophotograph is assessed as a large scale visualization tool for the communication of spatial information.

Notes: A review of the statistical testing of least squares photogrammetric bundle adjustments is presented. Various points are considered, including the effects of computation of the degrees of freedom and, in particular, assessing the goodness of fit of the adjustment residuals. Also discussed is how these tests relate to the assessment of the adjustment of the same data under different functional models.

Notes: It is often necessary to measure the resolving power of an imaging system comprising “off the shelf” components by a method that can also describe resolution in the object space. Furthermore, the results should allow useful comparisons to be made with alternative systems, where these have undergone a similar evaluation procedure. An example is given of measuring the resolving power of two imaging systems employing catadioptric objectives by a method that does not necessitate extensive laboratory tests, but utilizes the photographic product provided through field trials, or in the course of operational use. While the method reported does not claim to be a rigorous evaluation of the resolving power, it has been found to provide a convenient and practical guide to the image quality associated with a complete camera system, and its relation to the object space.

Notes: Digital photogrammetry has produced new products and brought automation to a number of traditional photogrammetric procedures. Some of the new products have been produced by the integration of data and information. With new products comes the need to assess their quality as this can have a direct effect on their potential use. Some of the new products and a number of parameters that affect their quality are discussed in this paper.

Notes: Books reviewed:M. Araya, Isprs HighlightsN. Channing and M. Dunn, British Camera MakersD. R. Wilson, The Care and Storage of Photographs. Recommendations for Good PracticeJ. R. Smith, R. S. Webb (1892-1976). From Shropshire to Paarl Via Geodesy and LesothoD. Shirvanian.European Space Directory 1997C. H. Wood and C. P. Keller, Cartographic Design: Theoretical and Practical PerspectivesO. Kö Lbl., Proceedings of the Oeepe Workshop on Application of Digital Photogrammetric WorkstationsI. J. Dowman, The Oeepe Geosar Test of Geocoding ERS-1 Sar DataJ. Jaakola and T. Sarjakoski, Experimental Test on Digital Aerial Triangulation

Notes: During 1994 a project was initiated by Ordnance Survey to investigate the requirement for completing the multi-million pound digital revision of 1:2500 scale mapping within Great Britain. This paper, although concentrating on this scale of mapping, discusses the revision policy issues that faced Ordnance Survey and the practical implications arising from implementing the policy for its 1:2500 and 1:10 000 basic scale mapping. Use of contractors was seen as a prime requirement as the resources available within Ordnance Survey were not sufficient to implement the full revision programme. This paper discusses the background to the task and considers the range of photogrammetric options and contractual and quality procedures required for the revision of the mapping over the next few years.

Notes: Members of the Institute of Engineering Surveying and Space Geodesy, University of Nottingham have been working on a collaborative project with staff of the British Geological Survey and the National Remote Sensing Centre Air Photo Group. During this project, experience of using the Intergraph ImageStation and ERDAS Imagine has been obtained. This paper presents some of these experiences which highlight the merits and limitations of digital photogrammetry at this present time. These are important issues not only for photogrammetrists but also for those coming into contact with photogrammetric operations through their potentially increasing availability in general image processing software. Although based on the authors' experiences, the paper also intends to provide a summary of digital photogrammetric systems and therefore issues are presented in a general way.

Notes: The paper entitled The Photogrammetric Society Analogue Instrument Project was published in The Photogrammetric Record, 14(82): 565-582 (October 1993) and contained, as Appendix A, an extract from the Archive concerned with the history of the Zeiss Stereoplanigraph in Great Britain. Further extracts have appeared in each of the subsequent issues, the last two being concerned with the range of mechanical projection instruments produced by the Wild company. This extract, the seventh of the series, completes the history of the use of this type of instrument in the UK by giving some details of the instruments produced by other manufacturers.The Wild instruments always employed straight space rods rotating in space about cardan joints. Perhaps in consequence their designs were sometimes described as obvious or unimaginative but they were undoubtedly most successful in practice. In contrast, most of the designs dealt with in this extract could never attract such adjectives. All of them incorporate novel features of design and one or two of them are so unusual in their approach that the short technical descriptions provided here cannot hope to explain adequately the working principles of their design. As an innovative designer of mechanical projection plotting instruments, Ermenegildo Santoni can rightly be singled out as a person who made an outstanding contribution in this field but, as the following paragraphs show, he was not alone in showing a remarkably inventive flair in devising solutions to the problems of rectification and restitution by mechanical methods.

Notes: derivation of spatial data from European Remote Sensing Satellite (ERS-1) Synthetic Aperture Radar (SAR) imagery is briefly described in this paper. A rigorous algorithm for space intersection applied in different geometric configurations and combinations, including the “same-side” image pair and the “opposite-side” pair, is illustrated. A simple error model is proposed by the authors to validate the error from different radargrammetric configurations. The experimental results show the possibilities and the limitations of obtaining three dimensional information from spaceborne SAR imagery with or without using ground control points. At the present stage, as a supplementary role in space cartography, the ERS-1 SAR imagery not only provides a new way to see the earth through clouds but also makes available an alternative tool to map the planet.

Notes: A system capable of automatically deriving the three dimensional co-ordinates of well defined binarized targets is described. Significantly, the system comprises cheap “off the shelf” hardware and software, requiring a minimum of development. Comparative tests using imagery obtained with a Hasselblad semi-metric camera and a 35 mm SLR camera are presented. By means of automated sub-pixel measurement, the results achieved are equivalent to those undertaken through manual target measurement using a first order analytical plotter.

Notes: This paper discusses the work carried out to obtain stereoscopic “photography” from airborne platforms with a Kodak DCS200 digital camera, as part of an investigation into the suitability of current digital camera technology for use in air survey. Details of the work, from the initial test flight in a Cessna light aircraft through to tests utilizing a Thruster microlight platform, are documented. The paper concludes with a summary of the present shortcomings in obtaining aerial photography for survey purposes with still video technology and discusses the future prospects.

Notes: This paper describes how to calculate all the essential matrices corresponding to five matched point pairs. Statistics are presented from tests with synthetic data and an example is given which has six solutions. A linear method for six point pairs is also described; the resultant essential matrix is uniquely determined by the six point pairs because the method is linear. The author also reviews some results, that have applications to photogrammetry, from other researchers in this field.

Notes: Unique place-names are essential for scientific fieldwork in Antarctica. This shorter contribution describes how duplication of place-names in British Antarctic Territory has been avoided by the systematic naming of geographically related features according to groups of associated ideas. One such theme, commemorating pioneers in the development of photogrammetry, recognizes the important contribution of photogrammetry to Antarctic mapping and research.

Notes: Books reviewed:K. B. Atkinson, Close Range Photogrammetry And Machine VisionR. A. Earnshaw and D. Watson, Animation And Scientific Visualization—Tools And ApplicationsR. A. Earnshaw, M. A. Gigante and H. Jones, Virtual Reality SystemsS. Macdonald, Mapping The WorldP. Fisher, Innovations in GIS 2A. Gruen, O. Kuebler and P. Agouris, Automatic Extraction of Man-Made Objects From Aerial and Space ImagesH. Campbell and I. Masser, GIS and OrganisationsS. C. Guptill and J. L. Morrison, Elements of Spatial Data QualityD. Shirvanian, European Space Directory, 1996D. R. Green, D.Rix and C. Corbin, The Agi Source Book for Geographic Information Systems, 1996K. C. Graf, Realistic Landscape Rendering Using Remote Sensing Images, Digital Terrain Models and 3D Objects

Notes: After giving an account of his personal experiences in the mapping industry, the author considers definitions of the terms photogrammetry, GIS and multimedia. The interaction of photogrammetry and GIS from the viewpoint of commercial suppliers is examined with reference to four companies: Intergraph, Leica, Laser-Scan and ERDAS. The main effects on the end user of a fast developing market are identified as the need to choose from an ever increasing diversity of products and services, and the opportunity to benefit from the changing presentation of height information. Finally the subject of professional institutions is discussed; any proposals for further fragmentation should be resisted.

Notes: Communication between the photogrammetrist and the land surveyor is essential for the overall success of a large scale mapping project, but each will have individual responsibility for specific stages of the project. Liaison is also required to achieve the maximum accuracy for heighting. Other interface areas between photogrammetry and surveying include the use of scanned images, airborne GPS and the development of the GIS market. The author emphasizes that co-operation will be vital for 21st century mapping, not only between technical disciplines, but also between the commercial, government and academic sectors of the mapping industry.

Notes: Based on his personal experiences with preparing specifications, the author defines the objective of a specification and lists particular problems that may arise when confusion of purpose exists. Guidelines for drawing up a specification are then presented. Finally it is emphasized that communication between provider and client is the most essential factor in achieving a successful specification.

Notes: Prediction of the future is implicit in most management decisions. This paper examines how far it is necessary to make this prediction explicit in deciding management strategy, what technical changes are likely to affect survey and photogrammetry in the near and medium term future, and the balance between the disciplines. The question is posed as to what extent management should invest effort and money in attempting to stay ahead of the game.

Notes: A standard digitizing tablet was used to measure objects off cropped enlargements (1:1000 scale), with an absolute accuracy of 0.75 m. Interior orientation for the enlargements was based upon camera reference marks captured from the original photographs, ranging from 1:6000 to 1:15 000 scale. Control for exterior orientation was provided by 1:1000 scale maps. Operational procedures are outlined, followed by results from eight sample photographs. Particular attention is devoted to errors that influence measurement accuracy.

Notes: The features and applications of the low cost analytical plotters manufactured by ADAM Technology are described. The ADAM Technology products (the small format MPS-2 analytical stereoplotter, analytical conversions for Kern PG2 and Wild B8 analogue stereoplotter and the 230mm format Promap modular system) are discussed.

Notes: This paper examines the rationale behind the design and development of the CP 2 analytical plotter and shows how the final product, in terms of both hardware and software, has been influenced by the needs of a commercial air survey company.

Notes: The history of survey and map production methods used by the Ordnance Survey of the Republic of Ireland is outlined and the significance of the decision, taken in the 1960s, to maximize the use of computer technology is emphasized. The four objectives of the Ordnance Survey's current programme of work (urban mapping, small scale database, large scale database and private sector support) require effort to be concentrated on resurvey procedures and no revision of old mapping is carried out. Details are given of equipment possessed by the Ordnance Survey and of staff distribution, followed by descriptions of procedures adopted for achieving both the small scale and large scale databases. Justification is presented for the decision to commit major financial investment to digital photogrammetry.

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: Ramsberg Castle is to be restored and renovated to allow a new use of the building. This requires extensive structural and architectural analyses based upon metric documentation. The façades of the castle were recorded photogrammetrically. Photography from the ground was impossible due to the steep terrain on three sides of the building. For this reason, the photographs were taken from a helicopter. A 4 × 5 inch Linh of Metrika réseau camera was used.Because of the adverse topography, only a few control points could be determined by on-site theodolite measurement. Therefore the control network was achieved by means of photogrammetric bundle triangulation. Stereorestitution was performed using an analytical plotter connected with a CAD system. Drawings at 1:50 scale were then derived from the as-built CAD model.

Notes: The paper entitled The Photogrammetric Society Analogue Instrument Project was published in The Photogrammetric Record, 14(82): 565-582 and contained, as Appendix A, an extract from the Archive concerned with the history of the Zeiss Stereoplanigraph in Great Britain. Further extracts have appeared in each of the subsequent issues.This extract, the sixth of the series, completes the history of the use of the various types of Wild instrument in the United Kingdom. It is concerned with the later post-war instruments, in numerical order, from the A7 Autograph to the A10 and therefore includes a note on one of the most popular and successful analogue plotting instruments ever produced, the Wild A8 Stereoplotter.At the moment, none of the instruments dealt with in this extract appear to be under immediate threat. However, their role as production instruments is fading fast in most organizations but they are being retained, often for training purposes.The Archive contains no mention of the last and most refined range of analogue instruments produced by Wild as their Aviomap (AM) series. With the benefit of hindsight it is now obvious that, at the time of their introduction, the transition from analogue to analytical techniques was about to take place at an accelerating pace. There is therefore no entry in the Archive for any AM or AM-U instrument; none (or perhaps only a very few) seem to have been imported into the United Kingdom.

Notes: This paper describes a project, the aim of which was to develop a computer assisted package for the teaching of analytical photogrammetry and especially the use of the ADAM Technology MPS-2 Micro Photogrammetric Stereoplotter.

Notes: A few of the many interesting aspects of the mind, life and work of Robert Hooke (1635-1703) are discussed, particularly some that are relevant to opto-mechanical photogrammetric plotters and cameras. Evidence from primary and secondary sources is presented which indicates that Hooke devised instruments with optical and mechanical components which later came to be used in photogrammetric plotters, that he recognized the value of perspective projection in accurate recording of terrain, and devised a “Picture-Box” for that purpose. The question of how far he progressed in photography in experiments with purple dyes is left open. These “photogrammetric” activities of Hooke's are shown to have been only a small part of his work in London which included duties as Curator of Experiments to the Royal Society, Professor of Geometry at Gresham College, and Surveyor to the City of London Authorities following the Great Fire in 1666.

Notes: Books Reviewed:S. F. El-Hakim, Videometrics IIJ. Denègre, Thematic Mapping From Satellite Imagery, A GuidebookT. C. Waugh and R. G. Healey, Advances In GIS ResearchJ. C. Muller, J.-P. Lagrange and R. WeibeGIS and Generalization. Methodology And PracticeP. M. Mather, Terra 2: Understanding the Terrestrial Environment. Remote Sensing Data Systems And NetworksB. Hofmann-Wellenhof, H. Lichtenegger and J. Collins, Global Positioning System: Theory and PracticeD. Shirvanian, European Space Directory 1995E. Falkner, Aerial Mapping: Methods And ApplicationsS. O. Mason, Expert System-Based Design of Photogrammetric NetworksS. F. El-Hakim, Videometrics IIID. Green and D. Rix, The Agi Source Book For Geographic Information Systems, 1995

Notes: Photographic surveying by Deville was published in 1895. This article marks the centenary of the publication of one of the earliest English language books on photogrammetry. Deville and his surveyors were responsible for the mapping of large areas in western Canada by photographic means. The techniques were explained in his book, originally written for his own staff when he was Surveyor General of Canada.

Notes: The lack of an accepted method of accurate and objective measurement of wound dimensions is a major obstacle to the assessment of effective wound management regimes. This paper addresses the problems associated with wound measurements and introduces a new instrument based on the principle of coded structured light. The instrument projects a sequence of parallel stripes of light onto the surface of the lesion. These patterns are observed by a video camera which is linked to a computer system where the images can be stored and processed. Using the positions of the focal points of the camera and the stripe projector, the computer calculates a three dimensional map of the observed scene by triangulation. This map is then used to reconstruct the original, healthy skin surface by cubic spline interpolation. The area of the reconstructed surface is the area of the wound. Its volume is sandwiched between the measured and the reconstructed surface. The system also calculates the depth and the circumference of the wound. The instrument measures the volume of the wound with a precision of about 5 per cent provided that the ratio of volume to area is greater than 4 mm.

Notes: The use of digital imagery, acquired through charge-coupled devices (CCDs) either by the scanning of hard copy film or direct capture through the use of a CCD camera, has fundamentally changed the photogrammetric environment. In order to fully exploit these digital image data, the photogrammetrist must employ system design, implementation philosophies and processing methodologies different from those of traditional film based photogrammetry. It is now possible for these new photogrammetric systems to be operated from low cost, high performance PC and Macintosh class commercial hardware, using vendor supplied software for user developed applications.This paper explores lessons learned and experiences gained from low cost, digital photogrammetric system development and CCD image exploitation. Examples and discussion presented in this paper include: (1) integration of user developed applications with commercial hardware and software; (2) user interface design; (3) validation of processing algorithms within the digital image domain; (4) system calibration; (5) digital image data handling, management and storage; and (6) image data compression. The film based photogrammetric system provides the point of departure to digital photogrammetry. Technical knowledge, system design and implementation and CCD image exploitation provide the experience.

Notes: The full provision of ground control points for oblique, small format photography used for mapping purposes is uneconomic because each photograph covers a small area of ground. This paper describes the implementation of a bundle adjustment program for 35 mm oblique aerial photography. Image co-ordinates are measured on enlarged prints, with a digitizing tablet driven by Carto MDSD software, and are then processed with the NLHBUNT program. The measurement system was proved by using vertical standard format photographs of a test block saturated with high quality ground control. Measurements taken with the MDSD system gave acceptable accuracy when compared with a set taken with a Zeiss P3 analytical workstation. A bundle adjustment was then carried out with the MDSD data; the results obtained compared satisfactorily with known ground values. A hand-held 35 mm Pentax LX camera was flown over the test site and three strips of 1:30 000 scale oblique photography were obtained. Following bundle adjustment, the empirical accuracy of derived co-ordinates was about 1.5 m in X, 3 m in Y and 2 m in Z. Factors affecting this accuracy are discussed and further developments of the system are proposed.

Notes: The author traces the development of the Swiss official surveying system from its origins according to the federal law in 1912 until the system of the renewed cadastre 93, standards for which were recently issued. He summarizes the techniques applied today in the official surveying system and describes the commercial situation of the private surveyors and surveying companies.

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: Following the disastrous fire in the State Apartments at Windsor Castle in 1992, a programme of photogrammetric surveying followed by archaeological recording was carried out by English Heritage. This paper details the background to this work, the provision of the photogrammetric surveys and the use and analysis of the data by the archaeology team.

Notes: The paper entitled The Photogrammetric Society Analogue Instrument Project was published in The Photogrammetric Record, 14(82): 565-582 and contained, as Appendix A, an extract from the Archive concerned with the history of the Zeiss Stereoplanigraph in Great Britain. A further three extracts have since been published to provide details of direct optical projection instruments used in this country and of the Vivian Thompson Stereo-plotter.This fifth extract deals with the Wild A5 and A6 instruments. Their introduction into the United Kingdom during and just prior to the Second World War, together with their important contributions to the war effort, make interesting reading. With a grand total of just five such instruments, they were well used throughout the period of hostilities.This extract also includes a note on the Wild A4 instrument, designed for close range photogrammetry. This was the last instrument in which Wild made use of projector lenses but it has been included at this point so that all of the Wild instruments which are listed in the Catalogue (and therefore included in the Archive) are dealt with in numerical order.

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.

Notes: Since 1990, the Center for Mapping at Ohio State University has been developing mobile mapping systems to automate and accelerate the collection of digital map data. These systems integrate the global positioning system (GPS) with inertial navigation units and imaging sensors to produce digital geographic data. They are modular and can be installed on various platforms, such as vans, trains and aeroplanes. New developments with the imaging system and the fully integrated data-processing environment are discussed in this article. The stereovision system enables the user to obtain three dimensional co-ordinates of any object in the field of view of the camera. Digital and video images, together with GPS positions, are stored in an object-oriented database, which merges data collected by airborne and terrestrial mapping platforms. Exploiting the enormous amount of information contained in the digital stereoscopic imagery is a challenging topic of current and future research.

Notes: Still video cameras are easy to handle, portable, digital image acquisition devices for close range photogrammetry. They allow fast object recording without being connected to a computer. As an example of the new camera type, the high resolution Kodak DCS200 is presented in this paper, combined with the DPA digital photogrammetric station used for image measurement and object reconstruction. The performance of this three dimensional measurement system is illustrated by calibration results as well as applications to high precision dimensional inspection in industry.

Notes: A description is given of the method used to assess the smallest practical photoscale that could be employed in a project to count and identify cattle, using small format aerial photography.

Notes: I. J. Dowman, Systems For Data Processing, Analysis And Representation, p. 145A. M. Morgado, Spatial Information From Digital Photogrammetry And Computer Vision, p. 147P. R. T. Newby, Mapping And Geographic Information Systems, p. 148D. A. Tait, Facing The Chance And The Challenge, p.154P. J. Curran, Eco Rio '94, p.155