VSM M 20 0 8 – Digital Heritage – P roc eedings of the 14
thI n terna tional C onf er enc e on V ir tual S y st ems and Multimedia
VSMM 2008
20–25 October 2008 Limassol, Cyprus
M. Ioannides, A. Addison, A. Georgopoulos, L. Kalisperis (Editors)
Proceedings of the 14 th International Conference on Virtual Systems
and Multimedia
Project Papers
Digital Heritage
This volume contains the Project Papers presented at VSMM 2008, the 14
thInternational Conference on Virtual Systems and Multimedia which took place on the 20 to 25 October 2008 in Limassol, Cyprus. The conference title was "Digital Heritage: Our Hi-tech-STORY for the Future, Technologies to Document, Preserve, Communicate and Prevent the Destruction of our Fragile Cultural Heritage".
The conference was jointly organized by CIPA, the International ICOMOS
Committee on Heritage Documentation and the Cyprus Institute. It also
hosted the 38th CIPA Workshop dedicated on e-Documentation and
Standardization in Cultural Heritage and the second Euro-Med Conference
on IT in Cultural Heritage. Through the Cyprus Institute, VSMM 2008 received
the support of the Government of Cyprus and the European Commission
and it was held under the Patronage of H. E. the President of the Republic of
Cyprus.
VSMM 2008
20–25 October 2008 Limassol, Cyprus
M. Ioannides, A. Addison, A. Georgopoulos, L. Kalisperis (Editors)
Proceedings of the 14 th International Conference on Virtual Systems
and Multimedia
Project Papers
Digital Heritage
Marinos Ioannides Editor-in-Chief Elizabeth Jerem Managing Editor
Fruzsina Cseh, Elizabeth Jerem Copy Editors
ARCHAEOLINGUA Cover Design
Cover image: The young woman here is holding a measuring stick for a Roman foot and is labeled as KTICIC, short for the Founding Spirit or the Creation. The mosaic can be seen in the Eustolios House, in the ancient Greco Roman city of Kourion in Cyprus that was destroyed by an earthquake in 365 AD. Photo: M. J. Ioannides.
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Permission to make digital or hard copies of portions of this work for personal or classroom use is granted without fee, provided that the copies are not made or distributed for profi t or commercial advantage and that the copies bear this notice and the full citation on the fi rst page. Copyright for components of this work owned by others must be honored. Abstracting with credit is permitted. To otherwise reproduce or transmit in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage retrieval system or in any other way requires written permission from the publisher.
© 2008 by The International Society on Virtual Systems and MultiMedia (VSMM Society) and individual authors
ISBN 978-963-9911-00-0
Published by ARCHAEOLINGUA Printed in Hungary by PRIMERATE
Budapest 2008
VSMM 2008
Digital Heritage
Proceedings of the 14
thInternational Conference on Virtual Systems and Multimedia
20–25 October 2008 LIMASSOL, CYPRUS
Abdelaziz Abid, FR Alonzo Addison, USA
Orhan Altan, TR Angelos Amditis, GR
Alfredo Andia, USA David Arnold, UK Alessandro Artusi, IT Manos Baltsavias, CH Juan A. Barcelo, ES Richard Beacham, UK Anna Bentkowska-Kafel, UK
J-Angelo Beraldin, CA Niels Ole Bernsen, DK Massimo Bertoncini, IT Nicoletta Di Blas, IT
Jan Boehm, DE Paul Bourke, AU Rosella Caffo, IT Panagiotis Charalambous, CY
Stavros Christodoulakis, GR Yiorgos Chrysanthou, CY Christis Z. Chrysostomou, CY
Paolo Cignoni, IT Sabine Coquillart, FR Andrea D’Andrea, IT
Uzi Dahari, IL
Adel Danish, EG Rob Davies, UK Andy Day, UK Martin Doerr, GR Michael Doneus, AT
Pierre Drap, FR Sabry El-Hakim ,CA
Ioannis Eliades, CY Dieter W. Fellner, AT
Maurizio Forte, IT Bernard Frischer, USA
Sakis Gaitatzis, CY Andreas Georgopoulos, GR
Luc Van Gool, CH Stephen M. Griffi n, USA Pierre Grussenmeyer, FR
Norbert Haala, DE Diofantos Hadjimitsis, CY
Klaus Hanke, AT Sven Havemann, AT
Sorin Hermon, IT Jeremy Huggett, UK Marinos Ioannides, CY
Babis Ioannidis, GR Charalambos Ioannidis, GR
Yiannis Ioannidis, GR
Wassim Jabi, USA Loukas Kalisperis, CY/USA
Sarah Kenderdine, AU Timo Kunkel, UK Marios Kyriakou, CY
Eleni Kyza, CY Andrew Laghos, CY Christos Lambrias, CY
Andreas Lanitis, CY Celine Loscos, UK Jose Luis Lerma, ES Katerina Mania, GR
Keith May, UK Despina Michael, CY Demetrios Michaelides, CY
David Mullins, IE Christiane Naffah, FR
Massimo Negri, IT Steve Nickerson, CA John Mackenzie Owen, NL George Papagiannakis, CH
Petros Patias, GR Sumanta Pattanaik, USA
Denis Pitzalis, FR Daniel Pletinckx, BE Chryssy Potsiou, GR
Mario Santana Quintero, BE C. Renaud, FR Julian D. Richards, UK
Seamus Ross, UK Nick Ryan, UK Robert Sablatnig, AT
Fathi Saleh, EG Donald H. Sanders, USA
Pasquale Savino, IT Michael Scherer, DE Holly Schlaumeier, UK
Roberto Scopigno, IT Stratos Stylianides, CY Georgos Stylianou, CY Nadia M. Thalmann, CH
Juan Carlos Torres, ES Olga De Troyer, BE Marina Tryfonidou, CY Nicolas Tsapatsoulis, CY
Giorgio Verdiani, IT Maria Luisa Vitobello, IT
Krzysztof Walczak, PL Aloysius Wehr, DE
Martin White, UK
International Scientifi c Committee
Yiorgos Chrysanthou Christis Z. Chrysostomou
Ioannis Eliades Diofantos Hadjimitsis
Andreas Hadjiprokopis Achilleas Kentonis
Andrew Laghos Christos Lambrias
Andreas Lanitis Anna Marangou Antonis Maratheftis Demetrios Michaelides
Stratos Stylianidis Georgos Stylianou Kyriakos Themistokleous
Marina Tryfonidou
Local Organizing Committee Conference Chair Marinos Ioannides CY
Co-Chairs of the International Scientifi c Committee (ISC)
Andreas Georgopoulos GR, Loukas Kalisperis CY/USA, Alonzo Addison USA Paper Review Chair
Andreas Lanitis CY
Workshop Chair
Denis Pitzalis FR
The offi cial carrier of the joint event Institutional Sponsors
Ministry of Education & Culture University of Cyprus
Supporters
Under the Patronage of H.E. President of the Republic of Cyprus
Cyprus Government
In cooperation with
Department of Antiquities in Cyprus Cyprus Government
In cooperation with European Union Projects
COINS CHIRON
Acknowledgements and Disclaimer
The VSMM 2008 joint conference has been partly supported by the VSMM Society, the Cyprus Government, the Cyprus Institute, The Cyprus University of Technology and the University of Cyprus.
The 38th CIPA International Workshop has been supported by CIPA, ISPRS and ICOMOS.
The 2nd EuroMed Conference has been supported by UNESCO-Cyprus Committee and the Cyprus Government.
However, the content of this publication refl ects only the authors’ views and the European Commission, Cyprus Government, VSMM Society, CIPA, ISPRS, ICOMOS, the Cyprus Institute, The Cyprus University of Technology and
the University of Cyprus are not liable for any use that may be made of the information contained in this proceeding.
Foreword
These conference proceedings contain a selection of papers that focus on multi-disciplinary research involving both Cultural Heritage (CH) Informatics and also the use of technology for initial data-capture and digitization, information data-processing, reconstruction, modelling, visualization, documentation and archiving, as well as visualisation of results and dissemination to the scientifi c and cultural-heritage communities and to the public. The contributions in these proceedings will defi nitely assist all experts involved in Cultural Digital Heritage in restoring, renovating, protecting, documenting, archiving, and monitoring history and prehistory, to secure this information for years to come. It is clear that a worldwide collaboration in this area will help make the past accessible to the present and the future.
Cultural Heritage is being transformed by the nature of digital representation of culture in which production, documentation, and distribution of an artefact are one and the same. Understanding and defining digital cultural heritage has implications for documentation practices and the experience of cultural institutions.
Digital devices provide unique access to archives and cultural exhibits, enhancing the capacity of museums and collections to encourage community building and civic engagement. Collection databases once used solely by museum professionals are now being made available locally and globally through the Web. Increasingly, access to cultural heritage is digital and experienced through electronic images and facsimiles. Digital tools and information and communication technologies are merging as the basis for preserving cultural heritage. Digital 3D modeling provides precise and complete documentation of cultural heritage objects and sites and should be used in conjunction with traditional techniques. Of great interest to the scientifi c community in the last few years, especially in the areas of architecture and preservation, are 3-D modeling, visualization and animation of cultural-heritage monuments and sites. The cooperation between photogrammetry and computer graphics has led to the development of new tools and techniques that are particularly useful for the documentation and archiving of cultural heritage in a digital format. These new tools and techniques include not only photogrammetry, but also 3-D reconstruction, visualization, animation and virtual reality. Technical achievements in modeling, rendering, and animation have made possible the creation of virtual environments, providing a convincing visual experience of cultural heritage structures and sites.
The island of Cyprus is a particularly appropriate venue for a conference on Virtual Systems and Multimedia dedicated to CH because of the long and rich pre-history and history of the island. The historical and archaeological context of Cyprus is the physical and ideal setting of this conference. The past story of Cyprus is the history of the interaction of the cultures and peoples of the lands surrounding the Mediterranean Sea, which was the central means of communication, transport, trade and cultural exchange between diverse peoples. Its history is important to understanding the origin and development of the Mesopotamian, Egyptian, Persian, Phoenician, Jewish, Greek, Roman, Arab and Ottoman cultures and, hence, is important to understanding the development of Western civilization as we understand and experience it today.
The roots of cultures and civilizations are embodied in their architectural structures and archaeological sites, and this cultural heritage should be preserved for future generations. The importance of preservation can be seen in the efforts of international organizations to document important structures and sites. UNESCO and ICOMOS have called for all national and international organizations that are responsible for manmade monuments to document cultural-heritage objects and sites with methods that include traditional and newer, innovative technologies. The integration of these technologies offers great promise and the use of digital technology in particular has rapidly changed documentation techniques.
The importance of Digital Cultural Heritage is evident by the participation and cooperation of a large number of people and organizations including the following:
– The 14th International Conference on Virtual Systems and Multimedia VSMM 2008, dedicated on Digital Heritage (http://www.vsmm.net/)
– The 38th CIPA International Workshop dedicated on e-Documentation and Standardization in Cultural Heritage (http://
cipa.icomos.org)
– The 2nd Euro-Med Conference on IT in Cultural Heritage.
We extend our thanks to all those, whose labour, fi nancial support, and encouragement made this joint event possible.
The International Program Committee, whose members represent a cross-section of Archaeology, Computer Graphics and Design, Architecture, Surveying, History and Engineering worked tenaciously and fi nished their work on time.
Especially Mr. Nikolas Valerkos, who designed and managed the webpage and Dr Andreas Lanitis who supervised the web-based submission system and guided the effort that published these proceedings. We would like also to express our gratitude to our co-organizers The Cyprus Institute, the Department of Antiquities in Cyprus and the Technological University of Cyprus. Finally, our institutional sponsors, the Ministry of Education and Culture, the University of Cyprus;
and our offi cial carrier, Cyprus Airways who provided money and ‘gifts of kind’ that made the conference possible.
Our Keynote Speakers, Javier Hernandez-Ros, European Commission, John Van Oudenaren, World Digital Library, Library of Congress, Massimo Negri, Europeana and European Museum Forum; Prof. Donna J. Cox, University of Illinois at Urbana-Champaign; Vassilios Tsingas, Elliniki Photogrammetriki Ltd; Kareem M. Darwish and Ahmed El-Shimi, Cairo Microsoft Innovation Center, are not only experts in their fi elds but also visionaries for the future of IT in CH. They promote the e-documentation of the past in such a way for its preservation for the generations to come.
Most of all we would like to thank the Cyprus Government, the European Commission, UNESCO WHC, ISPRS, ICOMOS, VSMM-Society and CIPA, that entrusted us with the task of organizing and undertaking this unique event and wish all participants an interesting and fruitful experience.
Marinos, Alonzo, Andreas, Loukas Limassol, Cyprus 2008
PROJECT PAPER INDEX BY SESSION
Data Acquisition and Remote Sensing in Cultural Heritage I
The Impact of GPS Tagging on Image Based Documentation and 3Dd Reconstruction of Cultural Assets . . . 1
G. PomaskaThe Importance of Considering Atmospheric Correction in the Preprocessing
of Satellite Remote Sensing Data Intended for the Management and Detection of Cultural Sites:
A Case Study of The Cyprus Area . . . 9
D. G. Hadjimitsis, K. ThemistocleousThe Harris Matrix Composer – A New Tool to Manage Archaeological Stratigraphy . . . 13
C. Traxler, W. NeubauerComprehensive Low-Cost Documentation of Built Heritage Using Social Networks,
Open Source Software and Rich Internet Applications . . . 21
R. FazalDigital Libraries
Planning of a Metric Historical and Documental Archive for the Realization of a City’s Cultural Portal . . . 31
M. D. Costantino, M. G. Angelini, G. CaprinoWeb Archive Switzerland
Collecting and Archiving Websites at the Swiss National Library . . . 39
B. SignoriBiodiversity Heritage Library: Building a Digital Open Access Library for Biodiversity Literature . . . 45
G. HigleyData Acquisition and Remote Sensing in Cultural Heritage II
A Multi-Resolution Methodology for Archeological Survey: The Pompeii Forum . . . 51
G. Guidi, F. Remondino, M. Russo, A. Rizzi, F. Voltolini, F. Menna,F. Fassi, S. Ercoli, M. E. Masci, B. Benedetti
Integrated Digital Technologies to Support Restoration Sites:
A New Approach Towards a Standard Procedure . . . 60
F. Chiabrando, F. Nex, D. Piatti, F. RinaudoThe Importance and Challenges of E-Documentation for the Conservation Field . . . 68
V. Lysandrou, G. Stylianou3D Digital Documentation for the Restoration of Cultural Heritage.
The Experience of the Old City of Aleppo Rehabilitation Project . . . 74
M. A. Núñez, F. Buill, J. Regot, A. MesaRecording and Documentation of Archaeological and Architectural Fragments
Using Automated Stereo Photogrammetry . . . 79
F. Henze, H. Burwitz, G. SiedlerThe Legacy of Colonial Buildings in Khulna City - An Approach to Digital Documentation . . . 86
H. RahamanExploiting the Contemporary Topcon Imaging Total Station for Cultural Heritage Recording . . . 91
A. Barakou, A. Georgopoulos, G. PantazisMobile Lidar Mapping For Urban Data Capture . . . 95
N. Haala, M. Peter, A. Cefalu, J. KremerDigital Archives Online
Integration, Management and Preservation of Archaeological Digital Resources in the Era of Interoperability and Digital Libraries:
The New Information System for the Superintendence of Naples and Pompeii . . . . 103
B. Benedetti, M. E. Masci, R. Cesana, A. VecchiJoining Italian Information System for National Achives: The Case of Rimini . . . . 110
G. BraschiOnline Access to Digital Collections – Design and Use of Museum Databases . . . . 116
I. Gil Fuentetaja, M. EconomouCollection Description in the European Information Landscape:
Michael the Multilingual Inventory of Cultural Heritage in Europe . . . . 121
K. Fernie, G. De FrancescoNestor – The German Network of Expertise in Digital Long-Term Preservation . . . . 129
N. SchumannDigitization, Documentation and Dissemination of Dimitrios Kaslas’ Archive . . . . 132
A. Kapaniaris, D. Economou, D. CharitosEscidoc – A Service Infrastructure for Cultural Heritage Content . . . . 138
N. Bulatovic, U. Tschida, A. GrosCH Digital Documentation and Communication
A Web Based Gis for the Byzantine Churches of Cyprus . . . . 147
A. Agapiou, A. Georgopoulos, M. Ioannides, C. IoannidisLessons Learned from Cultural Heritage Digitisation Projects in Crete . . . . 152
E. Maravelakis, M. Andrianakis, K. Psarakis, N. Bolanakis, G. Tzatzanis, N. Bilalis, A. AntoniadisA Multimedia Application for Exploitation and Virtual Fruition of Ancient Archaeological Artifacts:
The Experience of the 2nd Century Roman Balteus of Aosta . . . . 157
P. Salonia, T. Leti Messina, A. Marcolongo, A. Pozzi, S. ScolasticoMultimedia for Learning About Pre-Columbian Weavings in a Recreational Environment . . . . 164
D. Aracena-Pizarro, Y. Paredes-Orellana, J. Córdova-GonzalezICT
Tools for a Digital Reading of Andrea Palladio’s I Quattro Libri Dell’architettura . . . . 175
S. Baldissini, G. Beltramini, M. GaianiMultispectral Acquisition and Analysis of Ancient Documents . . . . 184
F. Kleber, M. Lettner, M. Diem, M. C. Vill, R. Sablatnig, H. Miklas, M. GauSystemisation of Knowledge for the Conservation
and Cultural Development of Piedmont’s Mosaic Heritage . . . . 192
C. Coscia, E. Fregonara, A. Mainardi, U. ZichEnrich: An Econtentplus Project for Creation of a European Digital Library of Manuscripts . . . . 201
A. Knoll, S. Psohlavec, T Psohlavec, Z. UhlířCH Digital Representations
Standards, Metadata, Ontologies: Culturaitalia Towards the Semantic Web . . . . 209
I. Buonazia, M. E. Masci, D. Merlitti, K. Ben Hamida, S. Di GiorgioMultifunctional Encoding System for Assessment of Movable Cultural Heritage . . . . 216
V. Tornari, E. Bernikola, W. Osten, R. M, Groves, G. Marc, G. M. Hustinx, E. Kouloumpi, S. Hackney3D Modeling and Semantic Classifi cation of Archaeological Finds
for Management and Visualization in 3D Archaeological Databases . . . . 221
A. M. Manferdini, F. Remondino, S. Baldissini, M. Gaiani, B. BenedettiStandards and Guidelines for Quality Digital Cultural Three-Dimensional Content Creation . . . . 229
G. De Francesco, A. D’AndreaToponyms as Horizontal Layer in Documenting and Listing Cultural Items . . . . 234
G. I. StassinopoulosA Versatile Workfl ow for 3D Reconstructions and Modelling of Cultural Heritage Sites
Based on Open Source Software . . . . 238
A. Koutsoudis, F. Arnaoutoglou, G. Pavlidis, D. Tsiafakis, C. ChamzasProcessing Cultural Heritage in Liguria: A Case Study Ingood Practice . . . . 245
E. Calandra, G. De Francesco, M. T. NataleVENUS (Virtual Exploration of Underwater Sites) Two years of interdisciplinary collaboration . . . . 250
F. Alcala, A. Alcocer, F. Alves, K. Bale, J. Bateman, A. Caiti, M. Casenove, J. C. Chambelland,P. Chapman, G. Conte, O. Curé, P. Drap, A. Durand, K. Edmundson, L. Gambella, P. Gambogi, F. Gauch, K. Hanke, M. Haydar, J. Hue1, R. Jeansoulin, S. Jeffrey, L. Long, V. Loureiro, M. Maïdi, O. Papini, G. Pachoud, A. Pascoal, J. Richards, D. Roussel, D. Scaradozzi, L. Sebastiao, E. Seguin, J. Seinturier, M. Serayet, E. Wurbel, S. M. Zanoli
Virtual Reality Applications in Cultural Heritage
Virtual Reality Technology in Museums: An Immersive Exhibit in the “Museo Leonardiano” . . . . 261
P. Fiamma, N. Adamo-VillaniThe Development of an e-Museum for Contemporary Arts . . . . 268
P. Patias, Y. Chrysantou, S. Sylaiou, Ch. Georgiadis, D. M. Michail, S. StylianidisA Web-Based Virtual Museum Application . . . . 275
T. Kunkel, M. Averkiou, Y. ChrysanthouRemote Virtual Access to 3D Photogrammetry: e-Vmv Virtual Museum of the Villa Reale in Monza . . . . 278
B. Raffaella, C. Branka, F. Francesco, D. OreniCultural Heritage Resource Information Systems
Come Back to the Fair . . . . 289
L. C. Walters, C. E. Hughes, E. SmithThe Communication Model of the Anthropology Museum:
Case of Multimedia Informational-Exposition Complex of the St.-Petersburg Kunstkamera . . . . 294
T. G. Bogomazova, J. A. KupinaDesigning Interoperable Museum Information Systems . . . . 297
D. Gavrilis, G. Tsakonas, Ch. PapatheodorouA Dynamic Workfl ow Management Framework for Digital Heritage and Technology Enhanced Learning . . . . 303
A. Al-Barakati, M. Z. Patoli, M. Gkion, W. Zhang, N. Beloff, P. Newbury, M. WhiteImage Analysis
Extraction of Numeric Data from Multilingual Archaeological Papers . . . . 311
H. PaijmansVideo Active – European Television Heritage Online . . . . 317
J. Oomen, V. Tzouvaras, A. HechtModeling Virtual Soundscapes:
Recreating The 1950s West Oakland 7th Street within a Multi-User Virtual Environment . . . . 322
G. KinayogluFocus K3D: Promoting the Use of Knowledge Intensive 3D Media . . . . 329
B. Falcidieno, M. Pitikakis, M. Spanguolo, M. Vavalis, C. HoustisAbstand: Distance Visualization for Geometric Analysis . . . . 334
T. Ullrich., V. Settgast, D. W. FellnerImage-Based Classifi cation of Ancient Coins . . . . 341
M. Kampel, K. Vondrovec, M. Zaharieva, S. Zam baniniExperimenting Timelines for Artefacts Analysis: From Time Distribution to Information Visualisation . . . . 349
J. Y. Blaise, I. DudekX-Ray Ct: A Powerful Analysis Tool for Assessing the Internal Structure
of Valuable Objects and for Constructing a 3D Database . . . . 357
J. Dewanckele, V. Cnudde, J. Vlassenbroeck, M. Dierick, Y. De Witte,D. Van Loo, M. Boone, K. Pieters, L. Van Hoorebeke, B. Masschaele, P. Jacobs
ICT in Museums
Cross-Media and Ubiquitous Learning Applications on Top of Iconographic Digital Library . . . . 367
D. Paneva-Marinova, L. Pavlova-Draganova, R. Pavlova, M. SendovaA Mobile Explorer for the Historical City of Salzburg . . . . 372
P. Costa, J. Pereira, A. Strasser, M. Strasser, T. StrasserThe Divine Project: Interactive Visitor Access to Archive
and Scientifi c Multimedia Via Networked Hand-Held Computers And Mobile Devices . . . . 380
R. Pillay, G. Aitken, D. Pitzalis, J-L. Coudrot, D. NicholsonVR and 3D Modeling
Digital Ocean: a National Project for the Creation
and Distribution of Multimedia Content for Underwater Sites . . . . 389
A. Dinis, N. Fies, N. Cheaib, S. Otmane, M. Mallem, A. Nisan, J. M. Boi, C. Noel, C. VialaThe Reconstruction of the Archaeological Landscape through Virtual Reality Applications:
a Discussion about Methodology . . . . 397
L. Vico, V. VassalloDetailed 3D Reconstruction of the Great Inscription of Gortyna, Crete:
Acquisition, Registration and Visualization of Multiresolution Data . . . . 404
F. Remondino, S. Girardi, L. Gonzo, F. NicolisThe Search for the Lost Garden of the Court of the Lions: Re-Animation of a Heritage Landscape . . . . 413
M. Ma, N. Pollock-EllwandDigital Ravenna. Explorating the Town Three-Dimensionally . . . . 419
L. Cipriani, M. BallabeniDigital Delphi: The 3D Virtual Reconstruction of the Hellenistic Plunge Bath at Delphi . . . . 427
A. A. Gill, A. R. FlatenThe River and the Desert Multi Media as Strategy to Expand a Public Space . . . . 431
G. RietherMemory of the Silk Road – The Digital Silk Rord Project . . . . 437
K. Ono, A. Kitamoto, M. Onishi, E. Andaroodi, Y. Nishimura, M. R. MatiniData Acquisition and Remote
Sensing in Cultural Heritage I
THE IMPACT OF GPS TAGGING ON IMAGE BASED DOCUMENTATION AND 3D RECONSTRUCTION OF CULTURAL ASSETS
Guenter Pomaska
University of Applied Sciences Bielefeld, Faculty of Architecture and Civil Engineering, Bielefeld, Germany gp@imagefact.de
KEY WORDS: GPS Tagging, Photo Communities, Imaged Based Documentation, 3D Object Reconstruction, Image Orientation
ABSTRACT:
Since digital technology removed the darkrooms from photography not only photogrammetric methods migrated to new concepts. A wide range of so far not imaginable applications of electronic image processing became popular. The classic photogrammetric procedures, known as mono-plotting and stereo-plotting, running on desktop environments today, making use of epipolar line geometry, autocorrelation, feature extraction, automatic texture extraction e.g. In CAD environments one can find numerous texture mapping and photo matching functions. And finally computer vision breaks into the field.
Despite the hype of laser scanning, due to the accessibility of digital compact cameras and single lens reflex cameras in conjunction with GPS loggers, the photograph as a container of high information density plays an important role in the field of data capture and object reconstruction of cultural heritage objects. Range based methods require additional image information to provide photo realistic 3D models, whereas photographs contain range and radiometric information.
This paper discusses the possibilities of GPS tagging and GEO coding and figures out some applications with aspects of digital photography, photogrammetry and computer vision. Amongst others it instructs into GeoSetter, the KML 2.2 photo overlay tag, taking use of the ARC 3D web service and discusses on what terms pictures can be used in photogrammetry.
1. INTRODUCTION
Today people share pictures in photo communities. End of 2007 the Yahoo software Flickr hosted more than two billion images world wide. Adding global position information to the EXIF data of an image is known as GPS tagging. GEO coding is the process to extend image data with non-coordinate based geographical information. Those kind of meta data is important for searching and finding pictures in a global world-wide data base of images. Google released Panoramio, extended Google Maps with Streetview and upgraded the Google Earth Browser with functionality for displaying very large images and panoramas. Microsoft Photosynth takes a large collection of photos from an object, analyses and displays them in a reconstructed 3D space.
The above mentioned technologies therefore take effect to documentation and object reconstruction of cultural assets. It has to be considered that the methodologies named here, work like the wiki principle. People publish material world-wide for a large community. Googles 3D warehouse and the campus and city modelling contribution exemplify that principle.
From the point of view of cultural heritage documentation 3D object reconstruction is still being considered as a supplemental.
High quality object reconstructions with respect to the structure of CAD systems are time consuming. There are surface models or solid models, both polygonal or curved based, known.
Texture mapping reduces the effort in geometric modeling and yields to photo realistic looking models. Utilizing scanning technologies is leading in point clouds of high density. Mesh models, generated from those point clouds approximate an objects outer skin. Existing image informationcan be used for additional texture mapping.
This contribution was acquired as a preparation for a future project mainly build from photographs. GEO referencing seems to be the proper method, ordering the huge amount of photos. A major focus points to software tools available from the Web. 3D object reconstruction in terms of usability will be discussed.
2. GPS TAGGING
A digital still camera (DSC) stores embedded in the image data some kinds of metadata. Additional information is related to image data structure, recording offsets, characteristics and other tags. Among this metadata 31 tags are defined for GPS information.
The standard for storing interchange information in image files is EXIF (exchangeable image file format). EXIF is part of the design rule for camera file system (DCF), operated by the Japan Electronics and Information Technology Industry Association (JEITA www.jeita.or.jp).The file recording format is based on existing formats. Compressed files are recorded as JPEG with application marker segments inserted. Uncompressed files are recorded in TIFF format. The specification is available from www.exif.org.
While GPS tagging deals with coordinate based geographical information, GEO coding extends image data about non- geographical based elements like postal addresses related to the coordinate data. A specification for storing text information related to image content is the IPTC (International Press and Telecommunications Council) standard. The standard enables interchanging of metadata between image agencies and VSMM 2008
Digital Heritage – Proceedings of the 14th International Conference on Virtual Systems and Multimedia
M. Ioannides, A. Addison, A. Georgopoulos, L. Kalisperis Project Papers
2
G. Pomaskaarchives. Another format for storing metadata is the extensible metadata platform (XMP).
Linking GPS data to image data is performed simultaneously by clicking the camera shutter if applying the appropriate hardware or by software synchronising camera time with the recorded track.
Nikon digital SLR cameras are compatible to Garmin and Magellan GPS receivers via the serial interface. Mobile navigation devices mounted on the flash adapter can be directly connected to the camera. Red Hen (www.redhensystems.com) provides an adapter for Nikon cameras and off-the-shelf GPS units to directly capture geospatial referenced images The GPS mounts on top of the camera putting it in full view of satellites and records latitude, longitude and altitude data to the EXIF header of each image. The physical integration provides hands- free use and the GPS data is displayed on the camera LCD.
Figure 1: GPS logger I-GotU, Sony GPS-CS1 and the Garmin etrex mobile navigation unit
Sony provides a small GPS logger for recording the position where photographs are taken. The GPS-CS1 is a small (9 cm / 3.5 in, weight 100 gram / 2 ounces) cylindrical device which the photographer carries with him while shooting pictures. It records the location and time. The supplied GPS image tracker software synchronizes the images with the latitude, longitude and time readings from the GPS-CS1 device.
A new GPS logger is I-gotU from Mobile Action, Taiwan This device is only 47 x 29 x 12 millimetre small and weights 21 gram. The storing capacity is 17.000 track points. Connection to the computer is realized via bluetooth or USB cable. The I-gotU GPS logger is targeted to the hobby photographer.
All units export data in multiple sharable file formats and are therefore compatible with mainstream software and web albums.
The Telepointer GTA (www.gta-geo.de) links the position together with the orientation, (direction of the exposure axis or viewing direction) directly to the image data. GTA uses that information in their software products supporting the process of texture mapping to buildings. So each photo carries the answer to the question "Where was it taken and in which direction is it looking.?" GTA provides service for 3d modeling and is targeted to the professional market.
Figure 1 illustrates the GPS-logger I-GotU (50 $US) and the GPS-CS1 (100 $US) compared to a Garmin etrex Venture(200
$US). Prices in parenthesis are roughly rounded. The differences in pricing can be taken as a performance indicator for the units. It has to be stated, that there is no barrier to act with a GPS mobile device during photo taking due to a high price or a bulky handling of a system.
Figure 2: Telepointer GTA mounted on a SLR camera (image source www.gta-geo.de)
Mobile GPS navigation devices like Garmin or Magellan do not record only the position. It is possible marking waypoints, saving tracks and finding positions in the field. Maps, waypoints and routes can be loaded into the internal memory from external sources. Easy to handle communication software between device and external computer belongs to standard delivery.
Figure 3: Garmin Trip & Waypoint Manager, import of the track log
Garmin comes with the Trip & Waypoint Manager software (see figure 3 for a screenshot) for reading out and storing data.
A recorded track log contains time and GPS position. If a track is saved for tracing back, the timestamp will be lost for saving storage capacity. With this information in mind we focus to the
3
The Impact of GPS Tagging on Image Based Documentation and 3Dd Reconstruction of Cultural Assetsapplication of loading the track log information into the EXIF data of the images using a Garmin etrex with the Trip &
Waypoint Manager and a freeware named GeoSetter. GeoSetter can be downloaded from www.geosetter.de. It is a multi- language freeware.
GPS tagging of images with GeoSetter starts with downloading the digital images from a camera into a subdirectory. In the same directory the GPS track log should be stored as a GPX format. GPX is a XML-based standard for GPS data. If one is interested in the complete GPS data set in NMEA format, use of software like visual GPS is recommended. Visual GPS is freeware and can be downloaded from www.visualgps.net.
Working with GeoSetter enables selection of images combined with a track log by synchronising camera time and GPS time.
Connection between photo position and track is automatically interpolated and can be edited manually via the integrated Google map information. During updating the images the IPTC information is offered by standard information coming from the Google database. Output of a complete track can be saved in a KML file format and imported directly into Google Earth.
GeoSetter does not write in the original image files, it stores a copy of the images including the updated information.
Figure 4: GeoSetter interface with images, track and image positions markers
3. IMAGE PUBLICATION AND DISTRIBUTION 3.1 Photo Communities
Picasa is a software application for organizing and editing digital photos, originally created by Idealab now owned by Google. Picasa acts as a Web album, people can upload their photos into web space and share the albums with an authorized community. Picasa started as Shareware. Google began offering Picasa for free download since July, 2004.
Flickr is an image and video hosting website, web services suite, and online community platform. It was one of the earliest Web 2.0 applications, developed in Canda by Ludicorp, a company founded in 2002. Yahoo bought that company in 2005. Flickr is a popular Web site for users to share personal photographs. Bloggers use Flickr as a photo repository. Its popularity became Flickr by its organization tools, allowing
photos to be tagged and browsed by folksonomic means. As of November 2007, it hosts more than two billion images
Figure 5: Screenshot of Flickr
Panoramio is a geolocation-oriented photo sharing website.
Currently, some of the photos uploaded to the site can be accessed as a layer in Google Earth, with new photos being added at the end of every month. The site's goal is to allow Google Earth users to learn more about a given area by viewing the photos that other users have taken at that place (source:
en.wikipedia.org). Panoramio is reachable under www.panoramio.com.
3.2 Google StreetView
Google Street View is a feature of Google Maps that provides 360° panoramic street-level views and allows users to view parts of selected cities and their surrounding metropolitan areas at ground level. It was launched on May 25, 2007. Google Street View displays photos that were previously taken by a camera mounted on an automobile, and can be navigated using either the arrow keys on the keyboard or by using the mouse to click on arrows displayed on the screen. Using these devices, the photos can be viewed in different sizes, from any direction, and from a variety of angles. (source: en.wikipedia.org).
Figure 6: Screenshot of Google StreetView
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G. PomaskaWith Street View Google comes under criticism. People are afraid that there privacy protection may be hurt by the image recording (Smile! You're on Google's camera).
3.3 Google Photo Overlay
With Google Photo Overlay it is possible to publish very huge pictures or panoramas inside Google Earth. An image has to be prepared as an image pyramid with tiles of 256 px. The sample given here is a panorama of original size 8176 x 1126 px. The image is divided into 231 tiles numbered in a predefined order.
The KML description reads as:
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.2">
<Document>
<PhotoOverlay>
<name>Ramingsmuehle</name>
<description>Ramingsmuehle</description>
<Camera>
<longitude>7.5642</longitude>
<latitude>52.5498</latitude>
<altitude>34.0</altitude>
<heading>0</heading>
<tilt>90</tilt><roll>0</roll>
</Camera>
<Style>
<IconStyle>
<Icon>
<href>http://www.imagefact.de/kml/
raming/ramingsmuehle-tiles/
ramingsmuehle_$[level]_$[x]_$[y].jpg </href></Icon></Style>
<shape>cylinder</shape>
<ViewVolume>
<near>10.0</near>
<leftFov>-180.0</leftFov>
<rightFov>180.0</rightFov>
<bottomFov>-23.396235</bottomFov>
<topFov>23.396235</topFov></ViewVolume>
<roll>0</roll>
<ImagePyramid>
<tileSize>256</tileSize>
<maxWidth>8176</maxWidth>
<maxHeight>1126</maxHeight>
<gridOrigin>upperLeft</gridOrigin>
</ImagePyramid>
<Point>
<coordinates>7.5642,52.5498</coordinates>
</Point>
</PhotoOverlay></Document></kml>
Fígure 7: PhotoOverlay details of a 8000 x 2000 panorama
The code snippet of the KML file demonstrates the photoOverlay tag. Including the tags for the shape, viewpoint (camera) and image pyramid information. It is obvious, that dividing the image into a pyramid of tiles requires a software- tool. I used the software PhotoOverlayCreator from the Centre for Advanced Spatial Analysis , UCL. Downloadable as a Java Archive from:
http://www.casa.ucl.ac.uk/software/photooverlaycreator.aspna The above given sample, displayed in figure 7, can be viewed from www.imagefact.de/kml/raming/ramingsmuehle.kml.
3.3 Microsoft PhotoSynth
Photosynth is a new technology to view photos on a computer platform. It was developed in a collaboration between Microsoft and the University of Washington.
A large collection of photos of a site or object is taken by Photosynth to analyses them for similarities, and displays them in a reconstructed 3-dimensional space. An object needs between 20 and 300 photos for 3D reconstruction. Pictures can be taken with different focal length lenses but must be presented in full format, since photosynth uses the EXIF data for further processing. After selecting the photos, no more interaction is required. The result will be uploaded automatically to the Web.
A user can navigate inside the scene by selecting the angle of view and the zoom factor. Information about the photo position in relation to one another is provided. With Photosynth fast access to gigabytes of photos is realized.
Photosynth needs installation of a plug-in for MSIE or Firefox and is running under Windows XP and higher. Access to Photosynth is given by http://labs.live.com/photosynth. Visit www.photosynth.com for the latest release of the software.
Figure 8 is a screenshot from a photosynth portal www.nrw3d.wdr.de. The broadcast station WDR collects from its audience photos of selected monuments and brings them together as a synth. Approximately 100 photos are brought together for that reconstruction.
Figure 8: “Synth” of Hermannsdenkmal,a German monument
4. 3D OBJECT RECONSTRUCTION
3D object reconstruction is the most sophisticated container of documentation . It allows examination from any point the user selects, generation of video sequences and virtual walk through.
Geometric modeling complies to the structure of the modeling tools. We distinguish surface models and solid models, polygon
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The Impact of GPS Tagging on Image Based Documentation and 3Dd Reconstruction of Cultural Assetsbased or curved based, and hierarchical polygon models.
Sources of modeling are range based or image based recordings. Imaged based modeling speeds the time for recording on site and provides range and radiometric information. Surface models often provide only the textured skin of an object. The structure of buildings are represented by solid models. Automatic shape recordings result in point clouds and polygon models. In this chapter we focus to some principals and applications of image based methodologies photogrammetry and computer vision.
4.1 CAD Photo Matching
Today one can find photo matching functionality in most CAD software packages. Photo matching is designed for two different tasks. First there is the problem to match a photo into a geometric model for texturing the environment or to visualize how a construction fits into its surrounding. The other task is to model 3D geometry from one photo.
For a successful photo matching, two pairs of parallel lines on perpendicular surfaces have to be set into the photos and an approximate scale is required. We follow here a sample worked out with SketchUp. In figure 9 one can detect the red lines for the x-direction and the green lines for the y-direction of the buildings local coordinate system. From the matched photo it is now possible to construct geometry in 3D space and to cut out automatically the textures needed.
One must consider, that in practice it isn’t such easy as written in the manual. A result with good quality is automatically done only in particular cases. Most often a lot of time consuming fine tuning has to be carried out. Observe the shadow in the final rendering or detect other artefacts like the lantern in figure 10.
In SketchUp the photo matches are handled as scenes, defining camera position and orientation. Applying the GPS reference of the photo to those values enables global positioning of the model.
The kind of photo matching in Google SketchUp is known from the earlier Apollo Photo 3D software.
Figure 9: Photo matched by setting parallel line pairs onto perpendicular surfaces.
Figure 10: 3D model constructed from one photo with texture extraction
4.2 Photogrammetry
Photogrammetry is defined as recording, measurement and interpretation of images or digital pictures with non-contact recording systems.
Applying photogrammetry minimizes the recording time on site and provides results with a high and reliable accuracy.
Conditions for the adoption of photogrammetry are availability of a calibrated camera, the appropriate evaluation software and the operators profound knowledge.
The methodologies are grouped according to the numbers and arrangement of photos. There are single image measurements (mono-plotting), stereoscopic evaluations (stereo-plotting) and multi-image evaluations existing. Particular cases are the single image rectification and the orthophoto production.
Single image rectification takes advance from the projective relationship between an object surface and the image surface.
With for control points on the object plane or two pairs of parallel lines, the transformation matrix can be determined to rectify an image.
A calibrated metric camera is not required. The rectified image is still a perspective, but the impact of camera rotations is eliminated. Image rectification is a common method in architectural applications. By knowing the ground dimensions from digital maps, elevation data can be easily derived from photographs.
Figure 11 displays the result of a workflow targeted to 3D modeling and use of non professional equipment, described in detail on the web under www.imagefact.de/rectify.
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G. PomaskaFigure 11: 3D modeling from rectified photos and digital maps It is not possible, to get exact geometrical information from one image. If only one image is available, additional object information is required. Mono-plotting is the process, to intersect measurements in metric photos with object shapes.
The orthophoto, rectified to a digital terrain surface model stands as a sample for such a method.
Two photos, taken with parallel exposure axis from a bar contribute to a stereo model. The stereo model can be viewed and evaluated by special equipment in 3D.
The first step in stereo-plotting is the interior orientation and image refinement. In case of images taken with digital cameras, the interior orientation (measurement of fiducial marks) is not necessary. But the image should be refined about the correction of camera parameters, the principle point position and lens distortion correction. The values are coming from the calibration certificate.
As a second step, reconstruction of the relative positions of both images to each other is required. This relative orientation can be done today automatically, by filtering interest points, as applied in the Z-GLIF Software from Menci. The result is a stereoscopic model.
Next a true scale and local coordinate system must be referenced for the absolute orientation of the model. Most common are control points in the object or a minimum definition of a local orientation and an object distance to evaluate in true scale.
After that two step orientation process, the evaluation of details applying point, line and polyline measurements in a CAD like environment can be accomplished. The parallax or disparity measurements can be taken in the stereoscopic model (anaglyph filtering) by setting a floating mark onto the model surface or in monoscopic mode placing the crosshair to the same point in both images. Automatic procedures are known as on-eye stereo.
Figure 12 is a screenshot from the Z-GLIF software, displaying the mono mode with two crosshairs and a depth map. Raw measurements should be overworked to the final CAD model and positioned into a global coordinate system as stated below.
Figure 12: Z-GLIF stereoscopic evaluation Software The most flexible method in recording complex objects is the multi-image arrangement, working after a triangulation principle. The orientation is an iterative triangulation process. It starts from a left and right image. Comparing corresponding points yields to the model. From now on a change between resection and intersection in space let grow the field of orientation points and camera stations. A final bundle adjustment combines photogrammetric measurements with additional observations in the object space and reports about accuracy and reliability of the image bundle. The measurement protocol of detailed vector information has to be refined with CAD software as well. A common used software system of this type is Photomodeler from EOS Systems Canada.
Figure 13: Exposure arrangement for multi-image photogrammetry with minimum of 3 photo positions Image modeler from Real Viz follows the philosophy to generate a complete complex model structure from basic shapes inside the photo evaluation software. Modeling takes place directly in the photos up to mesh editing functions. Direct texture extraction is a pro for this workflow. Autodesk has overtaken (amongst others) the company Real Viz in mid of 2008. That indicates the importance of 3D modeling by photographs and the possible growing demand on that kind of software tools.
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The Impact of GPS Tagging on Image Based Documentation and 3Dd Reconstruction of Cultural Assets4.3 Computer Vision
Use of calibrated cameras and manual operating seems to be a disadvantage of photogrammetry. Computer vision methods target to the use of non calibrated cameras and totally automatic model reconstruction approximating the object geometry by triangular surface meshes, textured with image data. A solution resulting in a disparity map, confidence map, triangular surface meshes and the texture mapped scene by stereo image pairs was introduced by Koch. (Reinhard Koch, 1994).
Part of the agenda of EPOCH (network of European cultural institutions) is the development of cost-effectiv 3D acquisition technologies. The ARC3D web service (www.arc3d.be) offers the possibility to upload an image sequence, utilizing the ARC 3D image uploader, to a server and analyse the 3D reconstruction downloaded from the server with the ARC3D model viewer (Vergauwen, Van Gool 2006).
After processing on the web network, the client downloads the findings as a compressed archive. The archive contains a file including the reconstruction information, for each image a thumbnail and the image texture, the camera data as a manifest file, the dense depth maps and the quality maps. The model viewer reconstructs on the client computer the 3D information.
It is possible to mask the images, eliminating sky e.g., before reconstructing the surface meshes and surface texture. Final results can be stored in several formats.
Figure 14: MeshLab output, textured model and meshes including camera positions
In a second step the model can be refined with the MeshLab software tool, provided by the Visual Computing Lab, Italy, vcg.isti.cnr.it. MeshLab is a mesh processing system for editing and rendering unstructured 3D triangular meshes. Since the ARC3D web service does not require any coordinate information, the geometric model is not referenced to a higher order system. Figure 14 displays the textured model of a portal on the left. Shown on the right are the 3D meshes including the camera positions. Positioning the origin of the object system into a camera position enables the global positioning via GPS tagging as explained in the following chapter.
5. OBJECT ORIENTATION
Photogrammetric processing can be performed in model coordinates or local object coordinate systems. Image orientation is known as relative and absolute orientation. While measuring buildings, a local system fixing (parallel to one façade) is common. Such a definition uses the seven degrees of freedom of a coordinate system. Three translations, three rotations and one scale. Additional measurements at the object (control point information, distance measurements) applied to a bundle adjustment improve the reliability. In most cases a model refinement is required. From raw measurements a consistent CAD surface model or solid model has to be constructed. Compilation of the raw measurements into a CAD format must be performed. Converting the camera stations as well enables for absolute orientation of the model.
Transformation of the origin of the local coordinate system into a photo position facilitates the orientation.
As introduced in chapter 2, the camera stations are GPS tagged.
Calculation of the azimuth between two stations of proper distance provides complete orientation of the model, translation and rotation. One point of the base line is identical with the models local origin. The azimuth confirms by complete model rotation. Converting the model to KML results in a placemark, referencing the geometry to the Collada format. We only have to alter the latitude and longitude in the KMZ archive. A 3D photogrammetric model is now positioned with satellite accuracy.
Figure 15: The textured model compiled to Google Earth
6. CONCLUSION
A photo is a container of high information density. Apart from drawings, text reports, measurements taken with scales, total stations or laser scanner the photo is a major tool for documentation of cultural assets. A photo hosts geometric and radiometric information. Utilising GPS tagging adds time and position of picture taking to the image data. Furthermore GEO coding refers to non-coordinate based geographical identifiers.
Those metadata can help searching after a variety of location- specific information. GPS tagging and GEO coding is the basic condition that people can share their photos in Web communities. The Web albums Picasa, Flickr and Panoramio have been introduced.
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G. PomaskaGoogle Street View, Google Photo Overlay and Microsoft Photosynth stay for new methodologies how photos can be presented via the Web in a 3D manner. Research goes in the direction of navigating in gigapixel images.
3D object reconstruction from photos starts from photo matching in CAD system, is performed by photogrammetric methods up to the fully automated computer vision systems.
The quality of a model must be seen with respect to a users requirement.
Including the camera stations into the reconstruction enables world-wide global positioning of a 3D model generated from photographs.
According to computer graphics rendering procedures the following statement is cited:
If you like it photo real, go out and take a picture.
Today we can extend:
… and don’t forget your GPS logger.
Remark: All the small examples presented in the text are used as a feasibility study for administrating a future large project.
Selection of the objects is accidentally. Usefulness depends on the particular requirements.
7. REFERENCES References from Journals:
F. Boochs, G. Heinz, U. Huxhagen, H. Müller, 2007. Low-Cost Image based system for Non-Technical Experts in Cultural Heritage Documentation and Analysis. The CIPA International Archives for Documentation of Cultural Heritage Volume XXI- 2007, ISSN 0256-1840, pp 165-170.
Reinhard Koch, 1994. Model-Based 3D Scene Analysis from Stereoscopic Image Sequences. ISPRS Journal of Photogrammetry and Remote Sensing, Elsevier Science Publishers B.V.
Rieko Kadobayashi, Akira Seike, 2997. A 3D Photo-Logging System for Easy and Effective Recording and Understanding of Archaeological Sites. The CIPA International Archives for Documentation of Cultural Heritage Volume XXI-2007, ISSN 0256-1840, pp 400-404.
Anestis Koutsoudis, Fotis Arnaoutoglou, Georg Pavlidis, Vassilios Tsoukas, Christodoulos Chamzas, 2007. Process Evaluation of 3D Reconstruction Methodologies Targeted To Web Based Virtual Reality. The CIPA International Archives for Documentation of Cultural Heritage Volume XXI-2007, ISSN 0256-1840, pp 423 - 428
Luca Menci, Fulvio Rinaudo, 2007. New Trends in digital Photogrammetry Teaching and Diffusion: The Z-GLIF Software. The CIPA International Archives for Documentation of Cultural Heritage Volume XXI-2007, ISSN 0256-1840, pp 487-490.
V. Tsioukas, 2007. Simple Tools for Architectural Photo- grammetry. The CIPA International Archives for Docu- mentation of Cultural Heritage Volume XXI-2007, ISSN 0256- 1840, pp 712-715.
Maarten Vergauwen, Luc Van Gool, 2006. Web-Based 3D Reconstruction Service. Machine Vision Applications, 17, pp.
411-426, 2006.
References from Books:
Guenter Pomaska, 2007. Web-Visualisierung mit Open Source.
Vom CAD-Modell zur Real-Time-Animation. Herbert Wichmann Verlag, Heidelberg.
References from Web sites:
www.jeita.or.jp Japan Electronics and Information Technology Industry Association
www.exif.org Specification of the EXIF data
www.redhensystems.com Photo mapping and video mapping hard and software
www.garmin.com Vendor of navigation devices
www.gta-geo.de German software and hardware distributor for 3D building modelling tools
www.geosetter.de Multilanguage freeware for GPS tagging of photos
www.panoramio.com Photo community, tagging your photos for Web search functions
www.flickr.com Photo sharing community
www.maps.google.com Visit Google maps for streetview www.casa.ucl.ac.uk/software/photooverlaycreator.aspna Software to create image pyramids for Google Earth photo overlay
www.imagefact.de/kml Web page driven by the author of this article, several KML samples amongst others
www.photosynth.com Microsoft Photosynth plug-in www.nrw3d.wdr.de German portal site collecting “synths”
www.sketchup.google.com 3D modeler SketchUp
www.menci.com Photogrammetry and laser scanner software and hardware
www.eos.com Photomodeler software
www.realviz.com Autodesk iImage Modeler, Stitcher and Movimento
www.arc3d.be Web service for 3D reconstruction from photos vcg.isti.cnr.it MeshLab software for working with 3D surface meshes
THE IMPORTANCE OF CONSIDERING ATMOSPHERIC CORRECTION IN THE PRE-PROCESSING OF SATELLITE REMOTE SENSING DATA
INTENDED FOR THE MANAGEMENT AND DETECTION OF CULTURAL SITES: A CASE STUDY OF THE CYPRUS AREA
D.G. Hadjimitsis* and K. Themistocleous
Department of Civil Engineering & Geomatics, Remote Sensing Lab, Cyprus University of Technology-31 Archbishop Kyprianos, P.O. Box 50329, 3603 Lemesos, Cyprus
*d.hadjimitsis@cut.ac.cy
KEY WORDS: Remote sensing measurements, atmospheric correction, cultural heritage sites, pre-processing
ABSTRACT:
Solar radiation reflected by the Earth’s surface to satellite sensors is modified by its interaction with the atmosphere. The objective of atmospheric correction is to determine true surface reflectance values by removing atmospheric effects from satellite images.
Atmospheric correction is arguably the most important part of the pre-processing of satellite remotely sensed data and any omission produces erroneous results. The effects of the atmosphere are more severe for where dark targets are shown in the satellite image.
In the management of cultural heritage sites, since temporal satellite images are required for monitoring purposes, the effect of the atmosphere must be considered. Classification techniques are also required to map land-cover changes in the vicinity of important cultural-heritage sites. Detection of important cultural heritage sites needs effective post-processing techniques. Indeed, any unsuccessful attempt to remove the atmospheric effects from the satellite remotely sensed images may cause non-reliable reflectance values. The paper presents a method of assessing the need for atmospheric correction, and addresses the importance of removing atmospheric effects in the satellite remote sensing of land-surfaces including cultural heritage.
1. INTRODUCTION
1.1 Remote Sensing for managing cultural heritage sites Satellite remote sensing has become a common tool of investigation, prediction and forecast of environmental change and scenarios through the development of GIS-based models and decision-support instruments that have further enhanced and considerably supported decision-making (Ayad, 2005;
Douglas, 2005; Hadjimitsis et al., 2005, 2006, 2007; Cavalli et al., 2007)
It was found from the literature that satellite remote sensing offers many useful and sometimes essential data for the mapping, monitoring and management of world cultural heritage sites, either natural sites such as parks or cultural sites such as archaeological sites and monuments (Arnaud, 1993). By blending together satellite remote sensing techniques with GIS, the monitoring process of such sites can be efficiently supported in a reliable, repetitive, non-invasive, rapid and cost-effective way. Indeed, satellite remote sensing can assist the achievement of the following:-
create up-to-date digital maps
assist in the identification and precise location of sites in the world that have certain characteristics so that they could become World Heritage sites if the associated country so desires.
help to delimitate management zones for conservation purposes
monitor land cover changes
assess damages caused by natural and/or human hazard.
assist the development of stereoscopic views so as to permit and obtain a digital elevation model of the landscape or some three-dimensional measurements of monuments through the use of satellite images and ground control points (obtained from GPS). Indeed, digital maps can be better realized.
In some areas in which an absence of recent maps of World Heritage sites exists and where such areas are often not easily accessible, recent satellite image coverage can be useful to produce new GIS layers providing the required information for a beneficial protection management of the site.1.2 Importance of atmospheric correction in time series imagery
Time series of satellite remote sensed data acquired at high spatial and temporal resolution provide a potentially ideal source for detecting change and analyzing trends. Since multi- temporal images are often acquired by different sensors under variable atmospheric conditions, solar illumination and view angles, an effective atmospheric correction is required to remove radiometric distortions and make the images comparable using the retrieved true reflectance values (Mahmoud et al., 2008). Several operational algorithms for relative and absolute atmospheric correction have been developed as shown by Hadjimitsis et al. (2004) and Mahmoud et al. (2008). The users of remotely sensed data must be aware about the contribution of the atmosphere to the at-satellite VSMM 2008
Digital Heritage – Proceedings of the 14th International Conference on Virtual Systems and Multimedia
M. Ioannides, A. Addison, A. Georgopoulos, L. Kalisperis Project Papers
10
D. G. Hadjimitsis, K. Themistocleoussignal especially in the case of time-series images. This paper addresses such issue.
1.3 Processing of satellite remotely sensed imagery After remotely sensed data have been received and undergone preliminary correction at the ground receiving station, the next step is to pre-process the data. Pre-processing refers to those operations that precede the main image analysis, and include geometric and radiometric corrections. Radiometric correction is more difficult than correction for geometric effects since the distributions and intensities of these effects are often inadequately known (Hadjimitsis et al., 2004), but unfortunately it cannot be neglected, particularly when multi- temporal images are to be interpreted. Techniques for correcting for sensor sensitivity changes, and for the topographic and view angle effects that are included in the radiometric correction category are well established. The most difficult step in radiometric correction is the removal of atmospheric effects.
1.4 Pre-processing
In the context of digital analysis of remotely sensed data, pre- processing is generally characterised by two types of data correction: (1) radiometric pre-processing which addresses variations in the pixel intensities (digital numbers, DN) and (2) geometric correction which addresses errors in the relative positions of pixels, mainly due to the sensor viewing geometry and terrain variations. Radiometric corrections are distinguished between calibrations, de-striping approaches, atmospheric corrections and removal of data errors or flaws (Mather, 2001).
Radiometric correction is more difficult than correction for geometric effects since the distributions and intensities of these effects are often inadequately known. Despite of the variety of techniques which can be used to estimate the atmospheric effect, the atmospheric correction remains an ill-determined step in the pre-processing of image data.
2. WHAT IS ATMOSPHERIC CORRECTION Any sensor that records electromagnetic radiation from the earth's surface using visible or near-visible radiation will typically record a mixture of two kinds of energy (Richards, 2005). The value recorded at any pixel location on a remotely sensed image does not represent the true ground-leaving radiance at that point. Part of the brightness is due to the reflectance of the target of interest and the remainder is derived from the brightness of the atmosphere itself. For example, for an area of interest that consists of cultural heritage sites an observed digital number of 85 might be the result of target reflectance, perhaps 25, plus an atmospheric contribution, perhaps of 60 (see Figure 1). The separation of contributions is not known a priori, so the objective of atmospheric correction is to quantify these two components so that the main analysis can made on the correct target reflectance or radiance values.
3. METHODS AND MATERIALS 3.1 Images
Archived Landsat-5 TM images of the Cyprus area acquired on the 30/01/2001, 11/5/2000, 11/9/98 and 3/6/1985 have been used (Figure 2). Quickbird image acquired on 23/1/22003 was
also used (Figure 3). The District areas of Paphos and Limassol that consist many cultural heritage sites have been selected to be used as pilot studies.
Figure 1: Atmospheric Interactions
Figure 2: Landsat TM image of Cyprus (11/9/98)
Figure 3: Quickbird- 0.6m resolution image of Paphos harbour area acquired on 23-12-2003
(castle and House of Dionyssos area)
3.2 Exploring the need for applying atmospheric correction Two simple methods can be used to find evidence suggesting a requirement for atmospheric effects in the available imagery:
image examination, and stretching (a) Image statistics
Examination of the statistics of multi-temporal images (consisting several cultural sites) provides a tool for deciding
