PHOTOGRAMMETRY AND CAD/CAM IN CULTURE AND INDUSTRY - AN EVER CHANGING PARADIGM

For the past ISPRS period 1996-2000, there has been remarkable changes in terms of photogrammetric research and applications in conjunction with CAD/CAM systems. Due to the dynamic nature of both CAD and GIS software as well as due to the ever demanding needs for new and challenging cultural and industrial applications, research has been driven far beyond the initial expectations. Innovative technologies for data acquisition, data processing, and information management, new cultural and industrial products, and their visualization have been developed. Additionally, the advances in technology have driven the evolution of new low-cost and user-friendly systems. Existing CAD/CAM systems have further improved their functionality and portability, giving thus a positive pull to development of new methodologies and tools for the integration of photogrammetric systems with CAD/CAM. New object-oriented measurement procedures support the transfer of photogrammetric technology to the industrial design, engineering and manufacturing sector, as well to architecture and archaeology. As a bottom line, all these changes have remarkably helped the photogrammetric society to pull the attention of many other scientific societies dealing mainly with the visualization of the photogrammetric output. Under the light of these changes, the paradigm has shifted from the pure photogrammetric recording to a holistic approach of recording, processing, archiving, managing, visualizing, and distributing information. This holistic approach builds an added value to the photogrammetric product, much higher than what for many years used to be. 1 CHANGING THE PARADIGM Documentation and conservation of cultural heritage are being increasingly seen as tasks of national − ultimately international − priority. Due to the digital techniques, photogrammetry now appears as more efficient and inexpensive; today’s user-oriented software is easier to handle by non-experts, thus widening the potential spectrum of application in architectural and archaeological recording. The main strength of photogrammetry, that is the reconstruction of an object surface geometry by remotely sensing it, has been recognized also by other disciplines than photogrammetrists. This important merit is currently being enhanced by : • a trend to move from traditional stereoscopy to multi-photo surface reconstruction • the low-cost digital image acquisition capabilities of the current technology • the potential of multi-sensor information collection • the wide acceptance of Information Systems currently enhanced by digital images as well • the wide spread of 3D modeling, visualization and web-authoring tools Patias, Petros International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B5. Amsterdam 2000. 599 As a result, Architectural Photogrammetry, as a discipline, has recently undergone profound changes. Even the term “Architectural Photogrammetry”, once from the focal points of Commission V, is not adequate any more to describe the wide range of recent developments. During the last ten years, we are witnessing an evolution of the paradigm from what was known as “Architectural Photogrammetry” to “Application of Close-range Vision Techniques and Spatial Information Systems to world cultural heritage”. CAD, on the other hand, can be considered a discipline somewhere between engineering and computer science /computer graphics. Over the last 20 or so years the meaning of CAD changed increasingly from computer aided drafting and the design of three-dimensional objects to a central part of the manufacturing process. CAD systems provide a computer internal representation of the product/object characteristics (geometry data and user dependent information). They are able to guarantee the communication between all the process steps (construction, manufacturing, testing, control, maintenance etc.) performed by some other computer aided techniques such as CAP (Computer Aided Work Planning), CAM (Computer Aided Manufacturing), CAT (Computer Aided Testing), CAQ (Computer Aided Quality Assurance). That development has been important for the interrelation between CAD and Photogrammetry. CAD systems serve as database for the integration of different types of data acquired by a number of measurement techniques including photogrammetry. 3-D object models can be generated, e.g. for the as-built documentation in areas such as industry and architecture, for 3-D indoor scene modeling and reverse photogrammetry, for object visualization, manipulation, animation etc.. In addition, CAD modeling concepts support the automated or semi-automated photogrammetric measurement using a priori knowledge of the object from a 3-D model. Summarizing, the common photogrammetric recording and reconstruction process has been increasingly replaced by a holistic approach of recording, processing, archiving, managing, visualizing, and distributing information. The integration of photogrammetric tools with existing CAD environments may lead to closer partnering between the measurement and end -user communities. Before studying the characteristics of the new paradigm it is useful to span through the recent history of the developments, as they have been reported through the symposia, the workshops and the related literature. 2 A REVIEW OF THE REPORTED TRENDS Since 1996, when the ISPRS Convention in Vienna took place, the trend was clear, and quoting from the symposium conclusions “...The largest number of papers for any Working Group concerned those in Architectural and Archaeological Representations (Working Group V/4). Over 45 authors had interesting examples to report. These ranged from the reconstruction of old monuments and buildings using conventional silver-halide photographs to the use of CAD modeling, video, surface matching, digital-still cameras and digital orthoimages to methodologies for the maintenance of inventories of historic cultural items... Again the involvement of more than one sensor was a feature of some of the more outstanding papers and the integration of multiple sensors into a system was a recurring theme...The Congress in Vienna portrayed the increased emphasis on stilland moving-video technology in the close range environment. Many papers detailed new applications, which have been discovered for video-photogrammetry. They are very exciting and represent the leading edge of this developing technology...” However, approximately 30 papers with a strong CAD/CAM component were presented in Vienna indicating the wide range of interest in CAD/CAM systems. That led Commission V to split the theme to the newly formed WG V/2, which was to deal with integration of CAD/CAM with photogrammetry, besides the old WG on Architectural Photogrammetry. WG V/2 also received the CAD/CAM related parts of the former WG V/3 "Structural and Industrial Measurements with Consideration of CAD/CAM aspects". The two WGs formed the next Terms of Reference : WG V/2 INTEGRATION OF PHOTOGRAMMETRIC SYSTEMS WITH CAD/CAM ! Survey of existing CAD/CAM systems (functionality, data formats etc.) ! Development of methodologies and tools for the integration of photogrammetric systems with CAD/CAM ! Development of CAD/CAM based object-oriented measurement procedures ! The transfer of photogrammetric technology to the industrial design, engineering and manufacturing sector WG V/5 WORLD CULTURAL HERITAGE ! Application of photogrammetry and spatial information system technology to the recording, mapping and visualization of structures and items of the World Cultural Heritage ! Incorporation of innovative technologies for data acquisition, data processing, information management, development of new products, and visualization Patias, Petros International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B5. Amsterdam 2000. 600 ! Development of low-cost digital systems for the recording and documentation of the World Cultural Heritage ! Fostering close cooperation with national and international groups ! Active promotion of the use of digital photogrammetric recording methodologies and products Since the main event in 1998 was the Commission V Inter-Congress Symposium in Hakodate, Japan, the status in progress, needs, trends and developments, regarding the WGs’ topics, had the opportunity to show up there. At that symposium a total of 51 papers were presented, covering, as expected, largely diversified topics, such as: • Imaging with new sensors (e.g. CCD-like scanners, laser scanners, digital cameras, video, etc.) • Sensor and data fusion (e.g. GPS + INS + image data, use of GPR, thermal sensors, MRI, etc.) • CAD based object recognition and measurement • Modeling and reconstruction (e.g. texture, artifacts, etc.) • Processing (e.g. vanishing lines, super-wide-angle lens distortion, edge detection, texture matching, simple software, emphasis in digital aspects, etc.) • As-built documentation • 3-D object reconstruction, visualization and Virtual Environments • Information Systems and image archives • Use of Internet and Multimedia for research and education The trends of the Hakodate Symposium were clear : • the use of new digital technology • the need for Information Managing Systems • the enhancement of communication between ISPRS and other scientific disciplines Regarding the needs in mapping and documentation of the world cultural heritage, we should note that : • There is a clear need for using technologically advanced tools, which offer wider flexibility and reduced costs. • There is a clear need in developing simple but efficient tools. • There is a clear need to adapt the widely used aerial photogrammetric algorithms and tools to terrestrial applications. • There is also a need to manage the recorded information. The development of Monument Information Systems (MIS) becomes vital. In 1999, the two WGs co-organized (in co-operation to 4 CIPA WGs, namely: WG3 (Simple methods in Architectural Photogrammetry),