Proceedings of the CIPA WG 6 International Workshop on Scanning for Cultural Heritage Recording

Böhler, Wolfgang

Bibliographic data

Monograph

Persistent identifier:: 830281592

Title:: Proceedings of the CIPA WG 6 International Workshop on Scanning for Cultural Heritage Recording

Sub title:: September, 1 - 2, 2002, Corfu, Greece

Scope:: 159 Seiten

Year of publication:: 2002

Place of publication:: Thessaloniki

Publisher of the original:: Publ. ZITI

Identifier (digital):: 830281592

Illustration:: Illustrationen

Signature of the source:: T 15 B 1303

Language:: English

Additional Notes:: Literaturangaben

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Böhler, Wolfgang

Corporations:: International Workshop on Scanning for Cultural Heritage Recording, 2002, Kerkira; ICOMOS/ISPRS Committee for Documentation of Cultural Heritage

Adapter:: International Workshop on Scanning for Cultural Heritage Recording, 2002, Kerkira; ICOMOS/ISPRS Committee for Documentation of Cultural Heritage

Founder of work:: International Workshop on Scanning for Cultural Heritage Recording, 2002, Kerkira; ICOMOS/ISPRS Committee for Documentation of Cultural Heritage

Other corporate:: International Workshop on Scanning for Cultural Heritage Recording, 2002, Kerkira; ICOMOS/ISPRS Committee for Documentation of Cultural Heritage

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2015

Document type:: Monograph

Collection:: Earth sciences

Chapter

Title:: 4. DOCUMENTATION OF ARTIFACTS

Document type:: Monograph

Structure type:: Chapter

Chapter

Title:: VOLUME BASED RECONSTRUCTION OF ARCHAEOLOGICAL ARTIFACTS. Martin KAMPEL, Robert SABLATNIG, Srdan TOSOVIC

Document type:: Monograph

Structure type:: Chapter

- 129 - dense grid would not result in any improvement. The quality and the processing speed of all following steps of treatment of the measured points are strongly dependent on the software used for this purpose. MENSI provides the 3Dipsos software which is designed primarily for engineering projects with the extraction of CAD-features from the point cloud. The treatment of irregularly shaped surfaces including triangulation and model generation is possible but is not always very effective. The single scans are registered into a common coordinate system using red spheres placed around the sculpture. The center of each single sphere is modeled in the software and the points of the scans are transformed using these positions of the spheres as common tie points. At least three spheres are needed for every observing point. The accuracy of these transformations is limited to the accuracy of the positioning of the points and thus, especially in close range applications, often not sufficient, therefore. The point clouds of the single scans were registered more accurately using the point clouds themselves for the calculation of the transformation parameters, as provided by the 3Dipsos software. The result of this registration process was an oriented point cloud of the statue. Because of the overlapping scans of parts of the surface, the density of the points had to be reduced using a spatial sampling resulting in a point spacing of 1mm. The resulting model consists of about 1.000.000 points on the surface of the statue (fig 2, 3). The following steps are the elimination of wrong points, e.g. occurring at edges, and the smoothing of the point cloud. 3Dipsos provides two different approaches for the triangulation of the point clouds. Firstly, a true 3D triangulation which requires a regularly spaced point cloud. The second method uses projection surfaces like planes, cylinders or spheres, and performs a 2.5 D triangulation on this reference surface. This can be useful for building the mesh, e.g. for a part of an arm, but on the other hand leads to single mesh arrangements that must be stitched together to achieve a complete model of the statue. The time needed for the generation of the complete model was a multiple as compared to the time needed for scanning. Reasons for this are firstly the poor calibration of the scanner which led to a higher noise in the recorded points and secondly the software that provides only basic support for the generation of triangulated surface models and thus is not optimal for this task. The noise in the data itself also led to a higher effort in time for the model generation, as a higher effort is necessary in the preliminary treatment of the point cloud (cleaning, filtering) prior to the modeling of the surface. PHOTOGRAMMETRY The parts of the statue containing seams between the copper sheets and rivets were recorded with stereo models using an analogue middle format camera Rollei 6008 metric. For the orientation process of the single stereo models, point markers were stuck onto the statue. 16 convergent images were taken in addition to the stereo images. The distances between selected marked points were measured directly to introduce a scale into the following calculations. After measuring the image coordinates of all marked points in all images, a bundle adjustment was calculated to determine the 3D position of the marked points . The coordinates of the points could be determined with an accuracy of about 0.3 mm. The features on the statue were plotted using an analytical plotter Zeiss P3 with MicroStation® as connected CAD-system. The features to be plotted were attributed very simply using different layers for rivets, rivet holes, the contours of missing Ki parts of the statue, the construction holding up the statue and other details like the remains of the crown or the loincloth. The final 3D vector data set can be viewed and plotted in various projections showing the metric correct position of these features in the plots (fig 4). VISUALIZATION For all further visualization tasks, 3D Studio Max®, a 3D visualization and animation software, was used. The data transfer was realized using Wavefront OBJ and AutoDesk DXF formats.

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