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:: 5. PROJECTS AND EXPERIENCES

Document type:: Monograph

Structure type:: Chapter

Chapter

Title:: DIGITAL PHOTOGRAMMETRY AND LASER SCANNING IN SURVEYING THE "NYMPHAEA" IN POMPEII. Gabriele Bitelli, Alessandro Capra, Antonio Zanutta

Document type:: Monograph

Structure type:: Chapter

- 118 - via reference points (method useful for registration of multiple scans); by automated techniques relying mainly on the recognition of the same flat areas on contiguous scans. browser (fig. 10), and distances interactively and immediately measured between couples of points. The successive step is the creation of the 3D mesh and the final 3D model, after a series of refinements that, as well known, in general require powerful software and hardware platforms. Three scans were realised for the Big Fountain with 80 mgon resolution, one central (4 frames averaged) and two laterals, and only a central scan acquisition for the Small Fountain. In order to better compare the results of the photogrammetric and laserscanning process, the same targets, whose coordinates were determined by a topographical survey, were used for the exterior orientation in both the two approaches. Figure 8 shows the phase of automatic localisation of the targets, based on their high intensity values, realized by 3D RiVIEW Riegl software for the nympheum of the “Flouse of the Big Fountain”; the coordinates of the targets were supplied as a separate file. The automatic localisation, and the subsequent use for stitching together different scans, was successfully tested using the program Laser Scanner Registration 1.0 (Bomaz et al., 2002); the results, after a decimation of the cloud points, are shown in figure 9. Fig. 8 - House of the Small Fountain: registering the scans by automatic identification and association of control points. Fig. 9 - House of the Big Fountain, after automatic registration of three scans and subsequent point decimation. The free visualisation software provided by the Riegl firm (or other programs) permits this combined cloud of points to be exported in .wrl format and easily explored by a VRML Fig. 10 - House of the Big Fountain, interactive exploration of the three co-registered point clouds by a VRML plug-in in a standard browser. 3. COMPARISON AND INTEGRATION OF THE TWO TECHNIQUES During these experimentations, some preliminary tests were realized in order to verify the accuracy gained by different techniques. Considering for instance about 40 differences in distance between couples of control points in respect to the values derived from the topographical survey we have: Table 1 - Accuracy test: differences for absolute distances in respect to values obtained by total station surveying (values in meters). mean min max st. dev. Photogrammetry (ROR+AOR) 0.002 -0.012 0.012 0.008 Photogrammetry (scaled model coordinates) -0.002 -0.021 0.011 0.010 Laser scanning (instrumental coord, system) 0.004 -0.020 0.022 0.010 Taking in account the above mentioned limitations of this model of laser scanning for short distances and other experiences in literature, it appears that the accuracy provided by laser scanning systems is today well comparable with photogrammetry, and for some systems is better. Some general considerations deriving from our experience can be briefly expressed. The advantages of laser scanning, some of these in common also with photogrammetry, with respect to traditional surveying methods for archaeological sites and structures, and in general for cultural heritage preservation and documentation, could be briefly summarized as: short data acquisition time; very accurate 3D models obtainable from high density point clouds;

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