See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/236155255 Monument Presentation Using Digital Architectural Photogrammetry Article · January 1997 CITATIONS READS 4 205 2 authors: Klaus Hanke Mostafa A-B Ebrahim University of Innsbruck King Abdulaziz University 83 PUBLICATIONS 494 CITATIONS 46 PUBLICATIONS 148 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: ALPINE AIRBORNE HYDROMAPPING View project Full Professor at King AbdulAziz Univeristy View project All content following this page was uploaded by Klaus Hanke on 02 June 2014. The user has requested enhancement of the downloaded file.
MONUMENT PRESENTATION USING DIGITAL ARCHITECTURAL PHOTOGRAMMETRY Klaus Hanke, Associate Professor Institute of Geodesy, University of Innsbruck, Austria Mostafa Abdel-Bary Ebrahim, M. Sc. Assiut University, Egypt, Doctoral Student at Innsbruck University, Austria KEYWORDS: Architectural Photogrammetry, Archaeological Photogrammetry, Monuments, Documentation, Digital Photogrammetry, Close-Range Photogrammetry, Digital Projector. ABSTRACT Digital photogrammetric methods have made their way also into architectural applications which is traditionally a rather conservative branch. Beside the programs and techniques that have been adopted from aerial photogrammetry mainly low-cost systems are used for architectural and archaeological applications. New strategies for data acquisition, restitution and presentation of the digital data are under development. INTRODUCTION DIGITAL METHODS Digital methods spread in all fields of photogrammetry Digital photogrammetry adds a variety of new features to today. Easy handling, the comfortable and clear that development. Origin of the digital images can either processing with widely accessible computer equipment be digital cameras or scanned analogue photographs. For and all the advantage connected to this (low cost of hard- the latter task the Photo-CD developed by Kodak has and software) have lead to its ultimate success. The proofed to be very useful. It dispenses the availability of digital images especially for close-range photogrammetrist from the necessity of owning an applications with Photo-CD and digital cameras as well as professional scanner and delivers a high amount of the valuable amount of data shows this field to be very geometrical stability and accuracy of the scanned photos suitable for digital photogrammetric solutions. [Hanke,1994 and Hanke et al.,1995]. Beside this, the compact disk is an excellent media for storing data without The classic results of architectural photogrammetry are loss over long time. Moreover this method is very well facade maps, profiles and perspectives. In addition to that, suited for application of already existing or archived metric 3D grids, surface and volume models in connection with photos up to a format of 4 x 5 inch with resolutions up to CAD systems come out of the spatial photogrammetric 4096 x 6144 pixels. Digital cameras of comparable quality restitution. As in other surveying branches the latter have are on the contrary rather expensive or are provided with the advantage of easy continuation of data processing a small image matrix or low resolution. A very strong and administration without restriction to single analog development in this direction is within sight. maps and plans. Regarding the photogrammetric restitution the advantage Rectification of metric photographs is also a classic of digital photogrammetric techniques become visible. method in photogrammetry. Originally there were only Very expensive analytical plotters become replaced by photos of planes which have been rectified, later there common available PCs or workstations. Digital methods of appeared also approaches to perform differential image matching and image correlation support the user in rectification of photos showing curved or general surfaces performing the inner and exterior orientation of the images of objects [Voizikis, 1983]. These approaches came to for further processing. their limits as they are restricted to surfaces of the form z = f ( x , y ) meaning that the third coordinate is only a Automatic processing of the image’s contents really is a smooth mathematical function of the x and y coordinates challenge in architectural applications. Other than in aerial which is very rare in architectural applications. photogrammetry the content we look for is not always Architectural objects are generally not to describe in that clear and very often not or very hard to describe by easy way because they have ledges, alcoves and niches, algorithms (even by knowledge based systems). Because hidden parts and especially old buildings have often rather of the extension in depth of the architectural objects with irregular surfaces. Therefore, generally a really spatial their prominent or set-off sometimes hidden parts of the (3D) reconstruction of buildings has to be performed also surface every smoothing algorithm must fail. No object because a trivial partitioning into single facades (e.g. with point can be used as an approximation for its neighbor as curved surfaces) is not always possible. we are used to do it in topographical applications. Between them could lie a difference in depth of several
meters. The solution for this can only be seen in a operation. The acceptance of respective lectures in continuos interaction between user and software. Once be architectural photogrammetry made the realization of a set to a line that has to be evaluated the software will be number of smaller and larger project in Austria and in able to follow it on its way. The information extracted from other countries possible. The participation at international this line can be e.g. used to restitute parts of an object scientific initiatives allowed to verify and advance own using spatial spline curves [Forkert, 1993]. Another developments. successive way is to use sketches of the required facade elements to extract these lines from the images The concept of the ”digital projector” approach is on one [Steilein,1995]. The progress in digital methods for hand a new rigorous digital photogrammetric tool and on architectural photogrammetry may lie in this sense rather the other hand takes into account the demand for an in an interactive and partly automatic support of the user object oriented, three-dimensional reconstruction of than in an indifferent full automation of the process. monuments. THE CONCEPT OF THE ”DIGITAL PROJECTOR” On the contrary to the conventional ”rectification” of metric photographs the ”Digital Projector’s” concept is a strict object oriented three-dimensional restitution of the whole At the Institute of Geodesy, Innsbruck University the authors made an effort to contribute to this development. object without almost any conditions and limitations. The The current contact to architects, conservationists and approach is based on a reversion of the situation during archaeologists led to a fertile and constructive co- exposure. Figure (1) shows the scheme of the approach. scanner, Photo-CD digital or analog camera (digitalisation of films) (data acquisition) image enhancement bundel adjustment (preparation for projection) (point cloud, orientation) CAD system 3D rendering video, Photo-CD, (frame- and surface model) (digital projection) printer, plotter ... Figure 1: Data flow of digital architectural photogrammetry The process of reconstruction of a monument to get a model that arise from that step will be used as a kind of virtual computer model happens in 3 steps (Fig. 2): In the ”projection screen” and can be of very different degree of first step the cameras inner geometry and its position and details. In the third step happens the actual reprojection of orientation during exposure as well as the building’s the photos [Hanke, Ebrahim,1996]. characteristic framework of outlines and faces is to be reconstructed mathematically. To get a homogenous Similar to a slide projector some selected photos are solution of the total object these elements are computed in projected to the surface model of the monument. The a so-called ”bundle adjustment” where a probable result of selection is done regarding the visibility and its direction of the whole measurement system will be created. Beside of projection. The ”Digital Projectors” own the same inner this way the restitution of the outlines may also come from geometry and relative position as the related cameras. an analytical plotters result. In the next step within a CAD These values come out of the bundle adjustment can be environment this framework will be reviewed and if different for all cameras. The result of this process is a necessary completed where also additional complete 3D computer model of the object from which measurements (photos, tape, theodolit, etc.) can be added. After that the 3D model will be closed defining faces between the structure lines and will be investigated for leakage performing a rendering process. The face
a) Frame model from bundle adjustment c) Surface model (”projection screen”) b) CAD-edited frame model d) Digital projection onto the model surface Figure 2: Steps creating a virtual computer model
Recommend
More recommend
