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Applications in Cultural Heritage Documentation.
Abstract
The importance of cultural heritage documentation is well recognized. ICOMOS and the International Society of Photogrammetry and Remote Sensing (ISPRS) joined efforts in 1969 and created the International Committee for Heritage Documentation, CIPA. This chapter reviews many of the successful recordings of cultural heritage from recent years.
... De este modo, en lo que a asequibilidad se refiere, los costos del proceso fotogramétrico son económicamente viables en comparación con la técnica LIDAR. En este caso, elegir la tecnología, el procedimiento y el flujo de trabajo adecuados, es siempre un desafío y depende del tamaño, complejidad y nivel de exactitud requerida (Grussenmeyer, Patias, & Hanke, 2008). Cada tecnología tiene ventajas y desventajas. ...
... Cada tecnología tiene ventajas y desventajas. En la mayoría de los casos la combinación de tecnologías y metodologías puede ser la solución más beneficiosa (Guidi & Russo, 2011;Grussenmeyer et al., 2008;Patias, 2006). ...
La emergente necesidad de información actualizada, junto a la falta de documentación adecuada de sectores históricos de ciudad, además del desarrollo tecnológico acelerado de la época, ha provocado la creación de diversas herramientas para el levantamiento de información geográfica, topográfica, y arqueológica, que pueden contribuir al estudio de las transformaciones urbano-morfológicas y a la documentación y protección del patrimonio edificado. Con estos antecedentes, este estudio pretende validar una metodología para la identificación y análisis de alteraciones arquitectónicas como urbanas, en el campo del patrimonio edificado. Para esto, se llevó a cabo un levantamiento detallado mediante fotogrametría aérea y terrestre, en base al uso de herramientas que generan datos bidimensionales como son el Drone DJI Phantom 4, Cámara Nikon D5300, Cámara GoPro Hero 3 Black Edition y un Smartphone Iphone 7. De igual forma, este estudio se complementó con un levantamiento tridimensional mediante escáner láser LIDAR. Los datos se obtuvieron en base a vuelos ortogonales con dron, los cuales se complementaron, mediante documentación parcial de fachadas de las edificaciones del El Barranco de Cuenca en Ecuador, con las otras herramientas bidimensionales y tridimensionales antes descritas. Este proceso se llevó a cabo en dos ocasiones, con un lapso de 4 meses entre sí, con el fin de identificar posibles cambios. Al completar el procesamiento de los datos, se encontraron dos casos en donde las edificaciones fueron alteradas en diferente magnitud. Además, se estableció la versatilidad de los instrumentos utilizados para la reconstrucción tridimensional de nubes de puntos en nuestro medio. En este sentido, el escáner láser LIDAR fue la herramienta que brindó mejores resultados, sin embargo, el levantamiento tomó más tiempo y fue más costoso; por otro lado, considerando la relación calidad-precio, el drone DJI Phantom 4 resultó ser el artefacto más recomendable para este tipo de estudios.
... Odpowiednia obróbka danych pozwala na zastosowanie zebranych informacji na kolejnym etapie. Dane konwertowane są do odpowiednich formatów plików i edytowane w środowisku programów klasy BIM i programów grafi cznych 3D [16]. Przy użyciu tych narzędzi następuje proces modelowania i projektowania. ...
... Appropriate data processing allows for using the collected information in the next stage. Data is converted into fi les of suitable formats and edited in the environment of BIM class programmes and 3d graphic programmes [16]. The process of modelling and designing takes place using those tools. ...
During the last 20 years of the 20th and the beginning
of the 21st century, the development of new technologies
allowed for their wide use in many disciplines, e.g. in
monument conservation. Protection of cultural heritage
monuments was given a new, previously unknown, form.
Owing to the technological and computer science revolution,
there appeared a new form of protection – virtualisation.
The turn of the 20th and 21st century was the beginning
of the new era of technology and computer science.
Development of those disciplines has signifi cantly infl
uenced the possibilities and range of heritage protection.
There began a new epoch in the sphere of technologies
applied in conservation, as well as computer science and
virtual systems.
... In the documentation of cultural heritage, selecting the right technology, devising suitable procedures, designing the workflow, and ensuring the final output meets technical specifications pose constant challenges [40]. Key determinants include the size and complexity of the object, along with the desired level of accuracy [41]. ...
Cultural heritage includes all tangible and intangible values related to a society's history, culture, and identity. Monumental buildings, which constitute an important part of the cultural heritage that has survived from the past to the present, are under many natural (disaster) risks such as earthquakes, fires, floods, tsunamis, and landslides, as well as many human-induced risks such as theft, wars, and vandalism. Disasters have various effects on the environment and society in which they occur, such as loss of life and property, sociological, economic, and psychological problems. Turkey has been home to many civilizations due to its location in the world; so today it hosts many cultural heritages belonging to these civilizations. On 6 February 2023, the 7.7 and 7.6 magnitude earthquakes centered in Kahramanmaraş caused heavy losses in eleven cities. In addition to over 50 thousand casualties, many cultural assets were severely damaged and some of them were destroyed. The subject of this study is Tuz Khan located in the center of Adıyaman Province. The study includes the documentation process of the building, which was heavily damaged after the earthquake, by the 3D laser scanning method. The research carried out in the study region indicates that utilizing orthophotos generated from terrestrial laser scanning data as a base can yield architectural documentation with the requisite level of detail. The orthophotos serve as a precise output that can be imported into a CAD platform and utilized as a reference for redrawing the primary break lines. This approach proves economically advantageous for conducting analytical surveys, presenting a quick solution, particularly crucial in the aftermath of natural disasters where time efficiency is paramount.
... Digitisation and three-dimensional modelling techniques make it possible to faithfully reconstruct the exact shape of objects or structures. Three-dimensional modelling can be applied in several fields of application, such as: (i) realization of data archives to support museum activities and historical collections; (ii) production of multimedia content and prototypes for web and app representation; (iii) production of three-dimensional scale prints for cultural dissemination and to reconstruct a duplicate faithful to the original; 2 of 22 (iv) study of an artistic asset from the topological and conservation point of view; (v) 4D monitoring for the evaluation of the state of conservation and for the analysis of all possible variations [3]. ...
Artistic, architectural and Cultural Heritage (CH) structures are often exposed to a high risk of damage caused by seismic events, natural disasters and more by negligence and poor state of preservation and conservation; the use of a series of technologies, based on digital acquisition and high-level data processing, allows the realisation of a three-dimensional model of high detail. In order to preserve structures of particular historical and architectural value, it is necessary to assess their structural stability. In addition, many structures, such as statues, have rather complex geometries. Therefore, it is necessary to identify a methodology able to transform the point cloud generated through a geomatics approach into a model suitable for FEM (Finite Element Analysis) analysis. This process, known as Scan to FEM, is addressed in this paper. The paper shows the case study of the “Colossus of Barletta”, a bronze statue dating back to the 5th century A.D. located in the city of Barletta, Italy. To analyse this structure, a suitable methodology has been developed which is based on the optimisation of the surface model of the structure; in this way, it is possible to obtain an efficient transformation from a digital photogrammetric model with complex geometry into a model suitable for structural finite element analysis. The digital photogrammetry technique was applied for the survey of the structure, which allowed us to obtain a very high-resolution dense point cloud and a geometrically accurate three-dimensional mesh model, i.e., in a TIN (Triangulated Irregular Network) model. Subsequently, the TIN was transformed into a quad mesh model (identifying a suitable reduction value) and finally into NURBS (Non-Uniform Rational Basis-Splines) to be optimised and imported into a finite element calculation software. This geomatics approach has validated an efficient Scan to FEM process; in fact, thanks to this methodology, it is possible to elaborate three-dimensional models with complex geometry and draw a series of considerations related to structural behaviour or specific restoration interventions.
... With the developments in image capturing and image processing, UAVs have become an alternative for cultural heritage documentation and have started to be used in diverse heritage projects. In a cultural heritage area, UAV applications are mainly focused on aerial documentation [1], observation, monitoring [2], mapping [3], 3D modeling [4] as well as producing digital orthophoto, digital elevation model (DEM) and digital surface models (DSMs) [5]. ...
Rapid development in UAV (unmanned aerial vehicle) photogrammetry made it preferable in many applications including cultural heritage documentation. Usability, quickness and accuracy of digital images have grabbed also the attention of archaeologists. Especially orthoimages by UAVs have become considerably significant in the field of archaeological heritage documentation since they are fast and accurate images of the object with high detailed information. However their accuracy and quality are the most important features of these images for archaeological documentation. The aim of this paper is to evaluate horizontal and vertical accuracy of an orthophoto taken by a fixed-wing UAV in an archaeological area. The evaluation is made according to ASPRS (American Society for Photogrammetry and Remote Sensing) Accuracy Standards for Digital Geospatial Data. The archaeological area, the name of which is Kubad Abad Palace in Beyşehir Province in Konya, is the only Anatolian Seljuk Palace structure that has survived to the present day. The study describes the orthophoto generation process and positional accuracy evaluation results within the frame of the importance of accuracy for archaeological documentation.
... Over recent decades, geomatics techniques have become fundamental in the work of cultural heritage surveying and documentation (Patias 2007;Patias et al. 2008;Tucci and Bonora 2015). There are countless examples where the latest technologies can help in recording and preserving heritage. ...
The new geomatic techniques and technologies for surveying an archeological excavation are not limited to obtaining more accurate data or more precisely geo-referenced positions on a map, as they can lead to new approaches and, indeed, raise the concept of different dimensions relating to the handled information. The techniques on offer are now fully 3D and, even more interestingly, can also permit to handle temporal information, that is, the evolution of operations over time. This allows scholars and technicians to build and maintain a wealth of vital knowledge documenting what happens during an excavation. This is further true when these are in urban areas, often known as “emergency excavations” from their distinctive logistics and timing constraints. The aim of this paper is to present, in a practical context, some of the many capabilities of 3D surveying performed through digital photogrammetry based on multi-view structure-from-motion approach in the field of urban emergency archeology. The information that can be derived from exploring three-dimensional models allows us to interact with realities that no longer exist, with the possibility not merely of recording their memory, but also of further studies and insights, even after a long period of time. In addition, the excavation itself is documented as it evolves, thus allowing the main phases of the process to be reconstructed retrospectively. The study case examined covers a small necropolis discovered in Rimini (Italy) in 2015. The results and the 3D final products can be managed through Geographic Information System (GIS) tools and, therefore, can easily be interfaced and integrated with other types of information on a different scale.
... Advantages of image-base methods are related to their level of details, economic aspects, sensor portability, handling in spatial limited environment and a short data collection time. Disadvantages remain in the post processing when the texture of the object is poor and the shape is complicated (PATIAS et al, 2008). ...
Resumen Este trabajo presenta las ideas y trabajos preliminares del proyecto Integración de Técnicas de Fotogrametría y Escáner Láser Terrestre para la Documentación Patrimonial (IFOTEL TIN2009-09939; Ministerio de Ciencia e Innovación, Plan Nacional I+D+i, 2008-2011), con el que se pretende buscar la mejora y optimización de la documentación del patrimonio cultural mediante la combinación de diferentes métodos, especialmente de fotogrametría (tanto terrestre como aérea mediante el uso de plataformas ligeras), técnicas de barrido láser (LÍDAR terrestre) y topografía, que aúnen las ventajas de todos ellos minimizando sus inconvenientes. Palabras Clave: DOCUMENTACIÓN, FOTOGRAMETRÍA, LÍDAR TERRESTRE (TLS), CÁMARAS NO MÉTRICAS. Abstract This paper presents the preliminary works of the Integration of Photogrammetric and Terrestrial Laser Scanner Techniques for Heritage Documentation Research Project (IFOTEL TIN2009-09939; Ministry of Science and Innovation, National Programme R+D+I, 2008-2011). The IFOTEL project aims with the improvement and optimization of heritage documentation by means of combination and integration of different methods and techniques, mainly close range photogrammetry (both terrestrial and aerial with light platforms), terrestrial laser scanner and surveying, joining the advantages of the different methods but also minimizing the disadvantages of each single technique.
... • Control and monitoring of the state of real and personal properties, actions that can be applied to the object and to its territory. Today technologies and methodologies in this field of application allow to record the position, size and shape, as well as generate very accurate and realistic 3D models in terms both of geometry and of textures, that are required in any project related to the conservation of CH, forming an important element of the documentation and analysis process (Patias 2007; English Heritage 2011). ...
The conservation and enhancement of our cultural heritage (CH) require an exhaustive study in terms of position, shape, colour, geometry and also of the historical and artistic features. Survey methods have polished data acquisition techniques in line with technological progress. Today’s electronic and IT technologies, that are the tools of modern Geomatics, allow the effective survey and representation of 3D objects in different scales: from architectural structures to sculptures and also archaeological findings. All these respond perfectly to all the shades that our rich and versatile heritage present. This report does not really aim at explaining analytically the methods of Geomatics. Its main aim is to reflect on the relation between Geomatics and CH, not only highlighting their meaning but also and above all, their roots in the history of survey.
... In this context the International Committee for Documentation of Cultural Heritage (CIPA) is one of the international committees of ICOMOS (International Council on Monuments and Sites) which has as main purpose the improvement of all methods for surveying of cultural monuments and sites (CIPA, 2012). A more completed study of the evolution of these applications is described by Haddad (2011) and Patias et al. (2008). ...
In this work it is performed a comparison of two methods for obtaining digital elevation models (DEMs) and orthoimages of
medium-sized archaeological sites (500-5000 m2). The photogrammetric methods analyzed consist in the use of a light aerial
platform applying the normal case of photogrammetry (vertical photographs and regular blocks), and the second one is based on a
network of oblique photographs, taken from a telescopic mast, using a DEM obtained from a terrestrial laser scanner (TLS) survey.
The main goal is to analyze the more efficient method for these studies taking into account variables such the working time, the
accuracy obtained in the final products, the visual analysis of final orthoimages, etc. This study has been applied to the same
archaeological site in two different epochs. The image acquisition was performed before and after a conservation intervention at the
archaeological site. The results have shown similar characteristics for both products (DEMs and orthoimages) and accuracies but the
density of DEMs and the visual analysis of orthoimages have shown differences that allows us to select the more adequate method
taking into account the characteristics of each case. Thus the DEMs obtained using the TLS survey has shown more density of points
while the visual analysis of orthoimages has shown a better behaviour (radiometrically and visually) in the case of vertical
photographs.
... In cultural heritage documentation, choosing the appropriate technology (sensor, hardware, software), the appropriate procedures, designing the workflow and assuring that the final output is in accordance with the set of technical specifications is always a challenging matter (Patias et al., 2008). The leading parameters are the size and the complexity of the object and the level of accuracy required. ...
Cultural heritage documentation projects very often combine different acquisition methods as tacheometry, photogrammetry and terrestrial laser scanning. In this paper we compare these three methods for recording of heritage buildings. Our test object is the medieval castle of Haut-Andlau (Alsace, France), documented in 2006-2008. This castle is of particular interest for our investigations since its architecture is the result of different construction styles completed over the centuries. Old buildings are rarely regularly shaped and most of their facades are made of very complex curved structures. The documentation of the castle became a true challenge, regarding the constraints implied on the one hand by the steep and abrupt terrain surrounding the castle and on the other hand by the dense and broadening vegetation close to the castle. It became rapidly obvious that a unique technique would not overcome the vegetation and relief obstacles. The main part of the data capture was based on TLS. For completion of the laser scanner data at occluded building parts and for accuracy assessment, stereoscopic as well as multi-image models have been captured. Advantages and disadvantages of the different methods will be discussed in this paper. A quality assessment leads to the analysis of the models derived from each technique and to a crucial experience for further campaigns.
Cultural heritage is an invaluable resource for societies. Inherited from past generations, it must be preserved and safeguarded for posterity. However, it is threatened by several factors, including natural disasters and those caused by human actions. In this regard, the need for conservation of cultural heritage is an indisputable reality. Digital documentation is considered an important tool, providing precision, in the recording of physical features and peculiarities of heritage. On the other hand, when acquired documents are digitally archived, they can be used for numerous purposes, such as conservation and management of heritage. In the instance of minor or major damage to built heritage, these archives can be highly useful in the restoration process. In recent years, due to considerable developments in technology and digital tools, the techniques used for documentation of historical buildings have been also significantly improved, leading to a better standard of monument conservation. Accordingly, recognition and exploitation of the most recent technologies and techniques in the field of cultural heritage are of primary importance. Deploying new methods of documentation significantly reduces costs, expedites the process of surveying, and also ensures an accurate output. This paper investigates the application of digital techniques of documentation in cultural heritage conservation. Additionally, it offers an overview of the advantages and limitations of the most widely used techniques, including terrestrial laser scanning, low-cost photogrammetry methods, and the application of unmanned aerial vehicle (UAV) platforms.KeywordsCultural heritageDocumentation techniquesPhotogrammetryLaser scanningUnmanned aerial vehicles3D modeling
Intelligent systems and artificial intelligence are used in many areas today. In this study, it was investigated how smart systems could be successful in evaluating the projects presented as final products within the scope of studio lesson in architectural education process. In line with this aim, the study was arranged with the educational design projects designed by the students within the scope of the architectural design studio, which is the most important basic unit of architectural education. Firstly, the projects prepared during the training process were assessed and graded by the jury. After that, 51 architects (architecture fourth graders) were asked to evaluate the educational structure projects obtained at the end of the training process over the delivered products. Five different criteria have been used in evaluations such as form, function, aesthetics, flexibility and authenticity. The assessments made by the architects and the jury members were paired and the data set was created. The numerical values obtained were trained and tested using intelligent system methods used to solve different problems in the literature. At the end of the study, evaluation scores and estimation percentages of intelligent systems were found. Intelligent systems seemed to come very close to the assessments that the jury made. The use of intelligent systems for the final product evaluation in architectural studios has been recommended.
Mining plays a very important role in the history of man. From the very beginning man's development has been accompanied by the extraction, processing and utilization of mineral substances. In the past, mining often exerted influence on economic, social, legal and cultural structures within society. The technological aspect must be emphasized as well, for the technical achievements in mining and metallurgy in combination with a far-reaching technology transfer were always an innovative and driving force - A motor of progress that has decisively influenced and furthered the development of a modem industrial society. The mining boom of the 15th/16th century in the Tyrol repeated a sequence which had already occurred with similar intensity and far-reaching consequences many centuries before. During the Bronze Age, between 2200 and 800 B.C., dynamic changes took place in the fields of mining and metallurgy in connection with alpine copper ore exploitation driven by the eager demand for crude copper on the newly established European metal market for bronze production. The all-time peak of copper mining was achieved with the formation of "early industrial" production structures in the Middle and Late Bronze Age. Alongside numerous further mining centres in the eastern and southern Alps the Tyrolean region still played a significant role. The existence of excellent preliminary studies of the historic mining activities in Schwaz conducted at the University of Innsbruck presents ideal prerequisites for researching the above-mentioned epochs from the Neolithic to the early Mediaeval Times, from which hardly anything is known. This article describes the cooperation of different scientific fields on this item and especially the role of surveying and geoinformation to integrate and support all these groups in their work to achieve that focused goal.
The basis of the photogrammetric reconstruction of the altar at the monastery / church are 2 historic photos from around 1920’s as well as a 3D documentation of the church from terrestrial laser scanning. The point cloud from the laser scan was the starting point for an approximate computation of the interior and exterior orientation of that image that also contains parts of the altar area that still do exist.
Using a projection of the recent geometry into the image allowed the analysis of changes of the altar ensemble since the time of image acquisition. Those parts that are still in situ are the origin for further action. Whether fragments and parts should be used further or newly positioned was decided in the next phase of reconstruction process. The focus of the first step of the workflow was at the outlines of the parts in the center of the altar. Using a monoplotting approach and assuming that the profiles are vertical and parallel to each other these object could be definitely compiled. Theses outlines also allowed an approximate determination of the interior and exterior orientation of the second historic photograph in which otherwise the complete connection to the recent altar area was missing.
The side parts of the altar showed to be more complicated for reconstruction. The difference in depth of the varying edges could not be distinguished any more in the images. Such, the sequence and form of the different edges was adopted, scaled and transferred from the central part of the altar to the peripheral ones. Using this geometric information it was possible to define the necessary projection planes for the monoplotting restitution of the visible outlines. A concluding rigorous control was accomplished by back projection of the geometry into both historical images.
Different approaches and tools are required in Cultural Heritage Documentation to deal with the complexity of monuments and sites.
The documentation process has strongly changed in the last few years, always driven by technology. Accurate documentation is
closely relied to advances of technology (imaging sensors, high speed scanning, automation in recording and processing data) for
the purposes of conservation works, management, appraisal, assessment of the structural condition, archiving, publication and
research (Patias et al., 2008). We want to focus in this paper on the recording aspects of cultural heritage documentation, especially
the generation of geometric and photorealistic 3D models for accurate reconstruction and visualization purposes. The selected
approaches are based on the combination of photogrammetric dense matching and Terrestrial Laser Scanning (TLS) techniques.
Both techniques have pros and cons and recent advances have changed the way of the recording approach. The choice of the best
workflow relies on the site configuration, the performances of the sensors, and criteria as geometry, accuracy, resolution, georeferencing,
texture, and of course processing time. TLS techniques (time of flight or phase shift systems) are widely used for
recording large and complex objects and sites. Point cloud generation from images by dense stereo or multi-view matching can be
used as an alternative or as a complementary method to TLS. Compared to TLS, the photogrammetric solution is a low cost one, as
the acquisition system is limited to a high-performance digital camera and a few accessories only. Indeed, the stereo or multi-view
matching process offers a cheap, flexible and accurate solution to get 3D point clouds. Moreover, the captured images might also be
used for models texturing. Several software packages are available, whether web-based, open source or commercial. The main
advantage of this photogrammetric or computer vision based technology is to get at the same time a point cloud (the resolution
depends on the size of the pixel on the object), and therefore an accurate meshed object with its texture. After matching and
processing steps, we can use the resulting data in much the same way as a TLS point cloud, but in addition with radiometric
information for textures.
The discussion in this paper reviews recording and important processing steps as geo-referencing and data merging, the essential
assessment of the results, and examples of deliverables from projects of the Photogrammetry and Geomatics Group (INSA
Strasbourg, France).
This project utilised three-dimensional scanning technology in the study of ancient Roman art and archaeology: Roman representations of faces executed in marble.
In the cultural heritage sector, three-dimensional (3D) scanning finds its primary application in documenting and reconstructing objects and structures mostly of simple geometry: bones, pottery, architecture or the imprint of whole archaeological sites (Adolf 2011). In forensic science, the face is interesting from investigative and probative perspectives, including both recognition and identification. Biometric methods of facial recognition have been part of a plethora of computer science-based applications used in the verification of identity (Davy et al 2005, Goodwin, Evison and Schofield 2010).
The aim of this initial project is to provide objective relevant measurements of key facial features from the two ancient Roman portrait statue three-dimensional scans, which will allow the delineation of relationships between individual portraits including formal and stylistics aspects. The work described in this paper proposal is truly multidisciplinary, it touches on many fields including : Classical archaeologies (specifically ancient art history in the period of the Roman Empire 31BC – AD400), Forensic Anthropology (specifically physical anthropology and human osteology, Facial Biometrics (specifically uniquely recognising humans based upon their intrinsic physical traits and features) and Computer Science and Statistics (specifically the analysis of large complex multi-dimensional data sets).
The Bronze Age cave "Les Fraux" at Saint-Martin-de-Fressengeas (Dordogne, France) has been discovered in 1989. This site made of a network of galleries of several hundred meters, is a field of investigation for several researchers. This paper will focus on three-dimensional contact free measurement techniques for a full 3D-documentation of the structural elements of the cave with some focus on cave art details. In this cave, most of the art is etched in the clay and follows linear, schematic and geometric designs. There are indeed several manmade depictions on the walls and other valuable remains of activity all around the cave. For the archaeologists, the documentation and recording started in 2008 should: -contribute to the accurate indexing of the surveys and images of the remains and collections as well as structural elements and sculptures; -guarantee the indexing compatibility of the data between the different groups of researchers involved in the excavation; -ensure the georeferencing of any type of object in the different parts of the cave. Different techniques based on Terrestrial Laser Scanning (FARO Photon 80), Digital Photogrammetry (CANON EOS 5D images) and Spatial Imaging System (Trimble VX) have been used. The aim of the documentation work is to generate a geometric and photorealistic 3D model from the combination of point clouds and photogrammetric images, for both visualization and accurate documentation purposes. The underground tunnels of the cave are linked to the above terrain with surveying techniques for an accurate georeferencing. The workflow from the raw data to the final PDF-3D model will be discussed. Emphasis will also be given to the deliverables, since the huge amount of data is not directly usable by the archaeologists.
Several recording techniques are used together in Cultural Heritage Documentation projects. The main purpose of the documentation and conservation works is usually to generate geometric and photorealistic 3D models for both accurate reconstruction and visualization purposes. The recording approach discussed in this paper is based on the combination of photogrammetric dense matching and Terrestrial Laser Scanning (TLS) techniques. Both techniques have pros and cons, and criteria as geometry, texture, accuracy, resolution, recording and processing time are often compared. TLS techniques (time of flight or phase shift systems) are often used for the recording of large and complex objects or sites. Point cloud generation from images by dense stereo or multi-image matching can be used as an alternative or a complementary method to TLS. Compared to TLS, the photogrammetric solution is a low cost one as the acquisition system is limited to a digital camera and a few accessories only. Indeed, the stereo matching process offers a cheap, flexible and accurate solution to get 3D point clouds and textured models. The calibration of the camera allows the processing of distortion free images, accurate orientation of the images, and matching at the subpixel level. The main advantage of this photogrammetric methodology is to get at the same time a point cloud (the resolution depends on the size of the pixel on the object), and therefore an accurate meshed object with its texture. After the matching and processing steps, we can use the resulting data in much the same way as a TLS point cloud, but with really better raster information for textures. The paper will address the automation of recording and processing steps, the assessment of the results, and the deliverables (e.g. PDF-3D files). Visualization aspects of the final 3D models are presented. Two case studies with merged photogrammetric and TLS data are finally presented: - The Gallo-roman Theatre of Mandeure (France); - The Medieval Fortress of Châtel-sur-Moselle (France), where a network of underground galleries and vaults has been recorded.
Automation in 3D reconstruction involves mainly two tasks: (i) image orientation and (ii) 3D scene reconstruction. Nowadays, automation in (i) can be considered solved for aerial photogrammetric projects, but a general and commercial solution is still pending in case of close-range image blocks. Here, the complexity and diversity of the network geometry make the automatic identification of the image correspondences a challenging task. In this paper we present a methodology to automatically orient a set of targetless close-range images taken with a calibrated camera and the following creation of 3D models with a multi-image matching algorithm. Several real cases, comprehending free-form objects (e.g. bas-relieves, decorations, etc.), building facades and images taken with UAVs are reported and discussed. Lastly, some preliminary results on a methodology for markerless camera calibration are presented.
Listed by UNESCO in 1987 as a World Heritage site, the world-famous Ming Great Wall stretches several thousands of kilometers
across northern China, and served as a massive military defensive system which in recent times has a unique historical, artistic
and scientific value. Due to historical reasons and lack of advanced technologies, construction resources and conservation
status of Ming Great Wall have not been investigated in any systematic manner; indeed, the extent of the Great Wall has not
even been measured. This has resulted in a shortage of reliable first-hand scientific information on actual size, spatially
resource distribution and preservation status of this World Heritage site. Driven by the urgent need to establish protection,
research, renovation and management of Ming Great Wall, a comprehensive investigation and spatial mapping was jointly organized
and completed by the State Bureau of Survey and Mapping and State Administration of Culture Heritage. High resolution digital
stereo models at 1:10000 map scale covering the whole length of the Ming Great Wall have been created by photogrammetric reconstruction
using nearly ten thousand aerial images. Spatial distribution and attributes of the wall sections, trenches and various subsidiary
facilities in the surroundings of the Great Wall were measured with the help of digital photogrammetry workstations and results
from field studies. Reliable and precise information about the Ming Great Wall has now been obtained and documented, including
surface lengths, resource distribution, and preservation status. For example, the total length of Ming Great Wall is 8851.8
km, of which 6259.6 km is of actual wall, 2232.5 km of natural terrain, and 359.7 km of trenches. In category lengths, 1828.8
km is constructed of stone, 3411.3 km of earth, 249.6 km in brick, 197.5 km of cliff wall and the rest 572.4 km of other means.
Such information provides the scientific basis and strong platform in helping to delineate areas needing protection, in planning
conservation and renovation programs, as well as digital archiving for posterity and web-based applications for modern promotions
of one of the world’s great attractions, the Ming Great Wall.
KeywordsMing Great Wall-aerial image-digital stereo model-surface length-stereo mapping
The importance of cultural and natural heritage documentation is well recognized at international level, and there is an increasing
pressure to document and preserve heritage also digitally. The continuous development of new sensors, data capture methodologies,
and multi-resolution 3D representations and the improvement of existing ones can contribute significantly to the 3D documentation,
conservation, and digital presentation of heritages and to the growth of the research in this field. The article reviews some
important documentation requirements and specifications, the actual 3D surveying and modeling techniques and methodologies
with their limitations and potentialities as well some visualization issues involved in the heritage field. Some examples
of world heritage sites 3D documentation are reported and discussed.
KeywordsPhotogrammetry-Laser scanning-Multi-resolution-Multi-sensor-Heritage sites
One of the most significant consequences of the introduction of digital 3D modeling in the Cultural Heritage field is the
possibility to use 3D models as highly effective and intuitive means of communication as well as interface to share and visualize
information collected in databases. Due to the usual complexity of architectural and archaeological artifacts or sites, their
digital models need be subdivided in sub-components and organized following semantic definitions in order to facilitate data
retrieval. This paper outlines a methodology to semantically segment complex reality-based 3D models, annotate information
and share the results within online open-source tools. The segmentation stage to subdivide and organize 3D models is based
on both automated and manual methods, giving priority to automated procedures that can ease and speed these steps but not
neglecting the user intervention to achieve accurate results. The segmented 3D models are then visualized in web-based systems
to allow data access to a wider range of users and enlarge knowledge. The methodology is presented and tested on large and
complex reality-based 3D models of architectural and archaeological heritage structures.
Compared with aerial photogrammetry, close range photogrammetry and particularly architectural photogrammetry isn’t limited to vertical photographs with special cameras. The methodology of terrestrial photogrammetry has changed significantly and various
photographic acquisitions are widely in use.
New technologies and techniques for data acquisition (CCD cameras, Photo-CD, photoscanners), data processing (computer vision), structuring and representation (CAD,simulation, animation, visualisation) and archiving, retrieval and analysis (spatial informationsystems) are leading to novel systems, processing methods and results.
The improvement of methods for surveying historical monuments and sites, is an importantcontribution to recording and perceptual monitoring of cultural heritage, to preservation andrestoration of any valuable architectural or other cultural monument, object or site, as a support to architectural, archaeological and other art-historical research.
Since the first shape-from-shading (SFS) technique was developed by Horn in the early 1970s, many different approaches have emerged. In this paper, six well-known SFS algorithms are implemented and compared. The performance of the algorithms was analyzed on synthetic images using mean and standard deviation of depth (Z) error, mean of surface gradient (p, q) error, and CPU timing. Each algorithm works well for certain images, but performs poorly for others. In general, minimization approaches are more robust, while the other approaches are faster. The implementation of these algorithms in C and images used in this paper are available by anonymous ftp under the pub/tech_paper/survey directory at eustis.cs.ucf.edu (132.170.108.42). These are also part of the electronic version of paper.
Commercial software of digital photography, realizing cylindrical or spherical panoramas, are becoming popular. They are delivered for tourist and documentary use. For instance they are suitable for quick documentation of field excavations in archaeology. In fact their principal application consists in the realization of active explorations known as QTVR (Quick Time Virtual Reality). It has already been proved that these panoramic images also have a metric use (Luhmann, 4, 2004), (Szelisky,Kang, 15,2001). The 3D final reconstruction of object is performed by bundle adjustment of multi-station panorama. Normally rotating cameras are used instead of mosaics (Schneider, Mass, 2204). The advantage of the stitching software consists in its economy compared to the rotating cameras. The analogy between surveying and photogrammetry is in the case of the spherical panoramas almost perfect. In fact the panoramic photos are produced for projection on a sphere of the photographs having as centre of common projection the centre of the sphere (Szelisky,12,1997). Then the sphere is mapped in the image plane by the so-called longitude-latitude projection. The image points can be regarded as analogical recording of the angular observations of a theodolite having its centre in the centre of the sphere. The spherical panorama can have a field of view up to 360°x360°. They could be the ideal "theodolite". Nevertheless the camera cannot be set correctly as a theodolite. It is necessary therefore to recover two angles to set up vertical the axis of the sphere as the bi-axial compensator in a theodolite. The estimate of the angular corrections is done by means of known directions or known coordinates of points (control directions and control points), obtained by traditional theodolite, or finally with geometric constraints as horizontality or verticality of straight lines. In order to evaluate the effects of a non perfect verticality of the principal axis of the spherical panorama, a computer programme has been written, following the steps: 1) creation of a set of points laying in the unit sphere regularly spaced along meridians and parallels; 2) projection of the points in the "cartographic" plane by the latitude-longitude projection; 3) rotation of the sphere alternatively about x and y axes of small rotation angles; and monitor the shifts of the projected points in the cartographic plane; 4) back estimation of the rotation angles; 5) angular correction. However the angular corrections are not still sufficient to guarantee a reasonable accuracy in the final 3D object compilation. The formation of the mosaic of photos doesn't happen without noises. The errors have nevertheless an evident systematic behaviour and they can be filtered out with interpolation polynomials whose parameters are estimated in correspondence of control points. For this reason the network of control points has to bee quite dense. When the terrain coordinates of the panorama centre are known, the correct image position for the control points is known, that we can compare with the actual position in the image, knowing the correction vector for any control point. Therefore the correction of the observed points in the panoramic image takes place in two steps: correction for rotation, with the estimated correction angles, then further correction computed by interpolation with the corrections estimated in the nearest control points giving a Gaussian weight to the control points. We present and comment some experiences of spherical panoramas produced with the software Stitcher 4 ®, by Realviz. The lens distortion is already corrected by the mosaicing software itself. But the main problem still consists in the noise occurring during the formation of the mosaic. There are different causes for the noise, the moving clouds in the sky, the persons and the traffic moving in the scene, the non perfect interior orientation parameters of the camera, the camera projection point off set from the rotating axis. The discussed examples are the panoramas taken 1) in Ancona the university campus, 2) Piazza del Popolo in Ascoli town, 3) Piazza del Campo in Siena. The used camera was an amatorial 35mm equivalent digital camera of 3 mb resolution. The panoramas have resolution of 10000x5000 pixel. Any pixel corresponds to 0.04 g, which is not a very high accuracy. The results are encouraging as far as control points is concerned. For example, in Piazza del Campo, a valid test area, having dimensions ranging from 100 to 150m in plan and 100 in height (the municipality tower), we took four panoramas, and with a reflectorless theodolite we surveyed 135 control points. The RMS of the residuals are 0.027 in planimetry and 0.009 m in height over 108 control points, observed at least in three panoramas whilst for the plotted points the results are not so good, the RMS of sigma naught are 0.16 m in planimetry and 0.05 m in altimetry for 358 points over a total amount of 385, and we had to discard the remaining 27. Similar results we got for the other test fields. So far the results are only partly satisfactory. There are still improvements to be performed: improve the resolution of the panorama, improve the quality of the stitching algorithms, improve the efficiency of the interpolation procedure.
The need for mapping small objects in such areas as archaeology, museum collections, medicine, and industry may be met by using close-range photogrammetric techniques. Requirements of these disciplines demand, in some instances, extremely high accuracy in an automated process for recording the geometry of objects, while in instances which involve numerous objects to be mapped an error-free but rapid procedure is necessary. Laser scanning techniques are likely the best and most reliable for these purposes. However, the costs associated with these techniques prohibit their use in many of the applications mentioned above. The authors have constructed a device to take advantage of the properties of a laser beam; by using the optical properties of a vertical laser line beamed from an off-the-shelf laser level, standard photogrammetric methods determine locations of these points on objects. Costs are kept low because measurement is done without the use of a laser beam detector to measure distance (hence, position) of points on objects.
In architectural surveying aimed to restoration and to conservation, close to the traditional two-dimensional vectorial representation in orthogonal projection, raster representation has gained considerable importance. Among all raster representations, the most widely-used is the digital orthophoto. The application of laser scanners as a new instrument for terrestrial survey together with firmly attached, high resolution and close range calibrated digital cameras, has permitted to obtain in straightforward way not only orthophotos but even to produce more sophisticated elaborations such as 3D orthophoto or solid image. These representations allow to get a vector representations via digitalizing in a single image. In the paper we will describe in detail a survey procedure that is based on an integrated photogrammetric - laser scanning system manufactured and marketed by Riegl LMS GmbH (high performance D imaging laser sensor + high resolution digital camera). A newly developed software allows to automatically extracted 3D orthophoto and so-called "solid images" from the hybrid data set (registered scan data and digital images) which can be subsequently used to easily create vector drawings by means of 2.5D digitalizing. This procedure is considered as an alternative approach to traditional digital close range photogrammetry, usually carried out in the activities of the photogrammetric laboratory of CIRCE - IUAV, to produce the well-known final representations: vectorial drawings and orthophoto. Considering that these products are in Italy the ordinary requests of a survey final user, such as architects or more generally restoration technicians, the authors have done a comparison not only on the achievable accuracy but also on time, costs and resources consumption that are necessary in real applications following the two procedures: the classical one based on traditional photogrammetry, and the new hybrid system approach based on photogrammetry -laser scanner integrated system. As test field the Arena of Verona has been chosen, such as significant application for the comparison just for the big amount of data collected by the photogrammetric laboratory of CIRCE during the photogrammetric survey campaigns (still in progress), and moreover for its own characteristics of an archaeological and architectural survey combination. The objective of the research is to offer the possibility to a surveyor to choose the best solution for representations productions, demanded by architects, restorers, etc., considering both accuracy and representation requests.
It is to the interest of both the photogrammetrist and the non-expert user that image-based measuring techniques and user-oriented packages applied to architectural and archaeological documentation be kept as simple as possible. In this context, the potential of single-image techniques should be exhausted, confining stereoscopic procedures to irregularly- shaped surfaces. This contribution discusses a monoscopic approach for regular 3D surfaces whose known analytical expression provides the missing equation. Products may be in both vector and raster forms obtained via monoplotting and orthoimaging, respectively. Further, in the cases of developable surfaces (e. g. circular cylinders) digital unwrapping of the original images can also be performed. Finally, the basic concept is tested with six non-metric photographs fully covering a small late-19 th -centrury railway water-tower having the shape of a right circular cylinder. The unwinded plot of the surface as well as the mosaic of the digitally unwrapped images are presented.
ThS20 ABSTRACT: The aim of this project is to evaluate the possibilities that the high resolution satellite image offers in the field of archaeological research. More specific, the present study concerns the identification of buried archaeological remains with the aid of the Pan- sharpened (fused) image Quickbird-2. For this purpose, the fused image (spatial resolution 0.70m and spectral resolution 4 bands), that covers an extended area of the archaeological site of Philippoi in N. Greece, has been used. The new image has been produced from the fusion of two ortho images. The latest have been derived from the panchromatic image and the multispectral image as well. The generation of the above two ortho images has been based on a DTM of the area, photogrammetrically produced, and on the Quickbird sensor model. The fusion has been established with the PCA technique. The fused image has been evaluated with statistical criterions. Enhancement technique, as PCA was applied to facilitate the optical interpretation for the detection of the revealing traces. Comparing the interpretation results with the results coming out from previous research, based on photogrammetric data, has been found out that both of them converge. The advantage of the use of the fused image is that it offers additional valuable information to the archaeologists and/or to other technology oriented experts, as for example information about the land use etc. Additionally, the high spatial resolution of it offers the possibility for an accurate surveying of the detected traces.
New techniques constantly seek to meet a growing demand for realistic photo- textured 3D models in architecture and archaeology. When only visualisation is required, the emphasis lies on visual quality rather than accuracy. But in architectural photogrammetry the primary requirement is mostly to produce accurate mappings under strict specifications. Hence, accuracy comes first; yet visual products can benefit from precise modeling. In this context, a treatment of cylindrical and conic surfaces is presented. The process for develop- ing them onto the plane (the basic way to represent such surfaces) is outlined and illumina- ted at the example of two large ancient towers in the framework of projects prepared for the Greek Ministry of Culture. But besides their metric utility, these products represent ideal photo-textures for draping the mathematical surface to generate virtual reality effects. The results of such successful photorealistic visualisations are presented and discussed.
In recent years, St. Mark's Square and the surrounding buildings have been the subject of surveying campaigns that have gradually used more modern techniques and instruments for both the survey and representation phases. St. Mark's Square represents a field of application of survey of a complex monument (in that it comprises a group of parts). As a whole, we refer to the composite as "the square" but it can be divided into different objects that are traditionally handled by different sectors of geomatics, topography, close range photogrammetry, aerial photogrammetry and terrestrial and aerial laser-scanning, among others. Each of these techniques has been used in surveying the square and has contributed to the geometric definition of the monument in its entirety. Clearly, the general reference system must be unique; this leads to problems connected to geo-referencing instrumental systems with diverse characteristics of precision that allow for survey at different nominal scales. As a result, the surveys conducted have different characteristics in the form of representation and in their precision. Some processed data can be compared to certain other categories; one example of this is the survey of the pavement, surveyed in its planimetry and its altimetry. In fact, in 1993, an altimetric survey was done for trigonometric levelling on a regular grid and photogrammetric survey of 100,000 stone tiles. More recently, the first survey using terrestrial laser-scanner was conducted (2001) and a year later, a laser-scanner image was realised from the air. Since the data deal with exactly the same area, it was deemed useful to compare them in order to gain insight on the expediency of using a certain technique, conditional on the scale and the type of representation. In terms of planimetric representation in raster form, photoplanes, orthophotos and precision orthophotos have all been produced. This processed data use diverse digital reference models acquired by solid modelling from numeric cartography, digital photogrammetry by means of matching, and from aerial laser scanners. Another important issue in all this is comparison of products by placing them in relation to the use intended of them, in order to verify the possibilities of economies and optimisation. Similar considerations can be made for the elevations of the buildings, such as the Basilica. The paper presents the various experiments done and illustrates the methods and results obtained, the processes of integration and the difficulties encountered.
Efficient and comfortable acquisition of large 3D scenes is an important topic for many current and future applications like cultural heritage, web applications and 3DTV and therefore it is a hot research topic. In this paper we present a new mobile 3D model acquisition platform. The platform uses 2D laser range scanners for both self localization by scan matching and geometry acquisition and a digital panorama camera. 3D models are acquired just by moving the platform around. Thereby, geometry is acquired continuously and color images are taken in regular intervals. After matching, the geometry is represented as unstructured point cloud which can then be rendered in several ways, for example using splatting with view dependent texturing. The work presented here is still "in progress", but we are able to present some first reconstruction results of indoor and outdoor scenes.
This paper presents an octree based method of three-dimensional reconstruction of objects using a combination of two different methods, Shape from Silhouette and Shape from Struc-tured Light, focusing on reconstruction of archaeological vessels. Shape from Silhouette is a method suitable for reconstruction of objects with handles, whereas it is unable to recon-struct concavities on an object's surface, such as inside of a bowl. Shape from Structured Light can reconstruct such concavities, but it often creates incomplete models because of camera and light occlusions. The purpose of combining these two methods is to overcome the weaknesses of one method through the strengths of the other, making it possible to con-struct complete models of arbitrarily shaped objects. The construction is based on multiple views of an object using a turntable in front of stationary cameras. Results of the algorithm developed are presented for both synthetic and real objects.
In the last few years, digital photogrammetry became a major tool in archaeology. Specialists in this area recognize the advantage of fast and accurate mapping. Moreover they use photogrammetric techniques in order to record and document the findings of an archaeological site or the whole excavation. Mainly in prehistoric sites, there are several different temporal levels of ruins and very often the site has been constructed upon other ancient or prehistoric cities (different levels). It is very important for the archaeological research to record, map and monitor all the different levels of an excavation accurately. Alongside, time is a valuable factor for the archaeologists who can not rely upon the time consuming mapping of the excavation with the traditional way. Digital photogrammetry gives to the archaeological research all the powerful tools for an accurate mapping and recording of the archaeological sites. The specific interdisciplinary experimental research took place in an archaeological site of an ancient city of Eleftherna in Crete, Greece. Particularly, the excavation holes have been photographed and processed at three different stages (days) of the excavation progress. DTM and orthophotos for each hole have been created in all different stages. Additionally, digital images have been acquired for small artifacts that were found during the excavation process and their 3D models have been created.
Consumer grade digital cameras are widely used for close range photogrammetric applications because of the convenience of digital images and the low cost of capture and reproduction. Since the introduction of digital cameras in the 1980s, there has been a strong divide between relatively inexpensive, low resolution, compact digital cameras, and relatively expensive, high resolution, professional digital cameras. In recent years, the improved affordability of SLR (Single Lens Reflex) style digital cameras has increased the use of this class of camera, to some degree displacing professional cameras. Digital cameras are quite often bundled with a consumer grade zoom lens that is designed for the quality of the image, rather than the geometric stability of the calibration. When these cameras are used for photogrammetric applications, it is common practice that a high quality, fixed focal length lens is purchased and used in preference to the zoom lens. Calibration tests were conducted on a range of different digital cameras, all within the SLR class, to ascertain the differences between zoom and fixed lenses when used with these cameras. Analyses are presented that indicate the differences between the two lens types in terms of accuracy, precision and stability and suggest that although acceptable results can be obtained using zoom lenses, a fixed lens provides superior results. 1.
The orthophoto is a powerful instrument of representation which combines radiometric and geometric properties. In architectural applications the orthophoto production cannot be performed by using the traditional orthophoto approach. True digital orthophoto is a new technique which uses several images and a complete DEM of the object in order to produce an orthogonal projection of complex objects. All the radiometric information hidden by central perspective in one image must be recovered by other images and the orthophoto production must choose, the best image to be used, one by one. Complete shape description can be easily achieved by using modern terrestrial laser scanner devices. The paper shows the true digital orthophoto production of the central door of the San Marco Basilica in Venice: the result obtained is a complete radiometric and geometric description of the studied object under examination.
There are many compelling arguments, worldwide, for the recording of indigenous art sites which are endangered by "people pressures". The Baiame cave painting in the Hunter Valley of Australia (lat. 33 S, Long 151 E) is one such site. Traditional methods for recording rock art sites are reviewed from the perspective of archaeologists, indigenous peoples, the general public and surveyors/photogrammetrists. Needs and expectations of these diverse groups can range from approximate sketches to 3-D computer models and animations. Previously a laser scanner was used in conjunction with digital photography to produce a realistic 3-D model of the Baiame cave (El-Hakim et. al., 2004). Some simple surveying measurements were needed to 'tie' the spectral information on the cave wall to the digital elevation model (DEM) defined by the laser scanning. A second attempt at modelling the same cave has recently been undertaken using surveyed control points, digital photography and automated image correlation software commercially available with the Leica Photogrammetric System to produce a DEM and orthophotography. The relative merits of both approaches are discussed and the implications arising from their adoption outlined. The output of such a 3-D processes are reviewed with respect to the present and possible future expectations of users.
Photo-textured 3D surface models, and orthophotography in particular, are most important photogrammetric products, notably in he-ritage conservation. However, conventional software typically uses surface descriptions obtained via 2D triangulation; additionally, it cannot handle image visibility. Ignoring multiple elevations and image occlusions is clearly too restrictive for a complex surface shape. Geometric accuracy and visual quality are then possible only with tedious human interaction during surface modeling but also orthoprojection. Yet, laser scanning allows today fast collection of accurate, dense surface point clouds and creation of 3D meshes. Close-range photogrammetry is obviously expected to take full advantage of this. The authors present their approach for an automated production of orthoimages from fully 3D surface representations derived from laser scanning. In a first step, the algorithm detects surface occlusions for the novel view. While common photogrammetric software needs operator-defined patches on individual original images as the source for image content, here all available images are combined for 'viewer-independent' texturing of the new image. To this end, bundle adjustment data allow all surface triangles to be back-pro-jected onto all initial images to establish visibilities. Texture blending is performed with suitable weighting, which controls the local radiometric contribution of each original image involved. Given more than two values, a statistical test allows to automatically ex-clude outlying colour data. The implemented algorithm was tested at the example of a Byzantine church in Athens to indicate that this coupling of laser scanning with photogrammetry is capable to automatically create novel views from several images, while com-bining geometric accuracy and visual quality with speed. Finally, future tasks and further elaborations are outlined.
Metric applications with commonly available image processing or graphics packages are often reported. Not specifically designed for photogrammetry, these tools have a limited range of uses and, not least, require a good photogrammetric understanding to avoid oversimplification or blunders. As a more rigorous low-cost approach, the tools of widely-used commercial graphics packages may be combined with suitable software to produce 'autonomous' units capable of reli-able photogrammetric work. Here, software introduced into the AutoCAD R14 environment allows mapping from stereo-pairs with monoscopic pointing. Two adjacent windows are used for the overlapping raster images where homologue image details are alternatively digitised as points, lines or polylines; in a third, the 3D vector output is directly produced via space intersection. Users may work with the collinearity equations or DLT. Rectification of planar detail is also includ-ed. The system is seen as a useful low-cost photogrammetric system for mapping in close range and can be consider-ably expanded. Furthermore, the important educational uses of such systems also need to be stressed.
Camera calibration has always been an essential component of photogrammetric measurement, with self-calibration nowadays being an integral and routinely applied operation within photogrammetric triangulation, especially in high-accuracy close-range measurement. With the very rapid growth in adoption of off-the-shelf digital cameras for a host of new 3D measurement applications, however, there are many situations where the geometry of the image network will not support robust recovery of camera parameters via on-the-job calibration. For this reason, stand-alone camera calibration has again emerged as an important issue in close-range photogrammetry, and it also remains a topic of research interest in computer vision. This paper overviews the current approaches adopted for camera calibration in close-range photogrammetry and computer vision, and discusses operational aspects for self-calibration. Also, the results of camera calibrations using different algorithms are summarized. Finally, the impact of chromatic aberration on modelled radial distortion is touched upon to highlight the fact that there are still issues of research interest in the photogrammetric calibration of consumer-grade digital cameras.
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.
For further maintenance of the medieval fortress it seemed necessary in 1997 to start a serious renovation of the whole complex of the various buildings. To record and document the situation before and compare it to the status after the renovation a photogrammetric recording was initiated. We used some of the existing data of this documentation and complemented it -at the beginning only for scientific interest -with own measurements to create a very detailed and photo textured 3D model of the fortress.
The stability and geometric quality of a Rollei d7 metric 5 digital camera equipped with a 5 megapixel CCD sensor and several metric features were investigated. From a series of calibration measurements it could be stated that the camera provides quite stable values of the interior orientation parameters. In addition, a narrow nearly circular cylindrical apse of a small church of the Romanesque period covered with frescoes was photographed with the d7 metric 5 . For the evaluation of the photos a new procedure for rectification of cylindrical surfaces was used.
Central catadioptric cameras are cameras which combine lenses and mirrors to capture a very wide field of view with a central projection. In this paper we extend the classical epipolar geometry of perspective cameras to all central catadioptric cameras. Epipolar geometry is formulated as the geometry of corresponding rays in a three-dimensional space. Using the model of image formation of central catadioptric cameras, the constraint on corresponding image points is then derived. It is shown that the corresponding points lie on epipolar conics. In addition, the shape of the conics for all types of central catadioptric cameras is classified. Finally, the theory is verified by experiments with real central catadioptric cameras.
Depth from focus (DFF) and depth from defocus (DFD) methods are
shown to be realizations of the geometric triangulation principle.
Fundamentally, the depth sensitivities of DFF and DFD are not different
than those of stereo (or motion) based systems having the same physical
dimensions. Contrary to common belief DFD does not inherently avoid the
matching (correspondence) problem. Basically DFD and DFF do not avoid
the occlusion problem any more than triangulation techniques, but they
are more stable in the presence of such disruptions. The fundamental
advantage of DFF and DFD methods is the two-dimensionality of the
aperture, allowing more robust estimation. These results elucidate the
limitations of methods based on depth of field and provide a foundation
for fair performance comparison between DFF/DFD and shape from stereo
(or motion) algorithms
The identification of sites within forested areas is one of the remaining unresolved issues for archaeological prospection. Airborne laser scanning can be a solution to this problem: due to the capability of penetrating forest to a certain degree (depending on the vegetation density) the determination of the terrain surface is even possible in wooded areas. To be able to identify archaeological structures, archaeologists have to interpret the resulting topographical data of a filtered ALS scan. This does not pose major problems with large structures. Smaller fea- tures, however, are much more difficult to identify, because their appearance in an ALS point cloud is very similar to natural and recent features, as for example dense brushwood, or piles of twigs or wood. Therefore, to eliminate potential sources of error, a high quality separation of terrain and off-terrain points is essential for archaeological interpretation while maintaining a high point density of the ALS data. Using conventional ALS systems, the possi- bilities to classify terrain and off-terrain points are limited and the results - especially in forested areas with dense understorey - are far from ideal for archaeological purposes. This paper will demonstrate how the new generation of full-waveform ALS systems can be used to get a much better classification of solid ground and vegetation cover and consequently DTMs, which can be interpreted archaeologically with much more confidence.
We address the main issues in real-time visualization and interactive manipulation of highly textured sur- faces. For applications such as cultural heritage, achieving this will give a vista to scientists, conserva- tionists, historians, and visitors for looking at and studying important frescoed surfaces in virtual reality. Since photo-realism is of utmost importance, it became apparent that many problems related to geometric and radiometric distortions must be solved. As a case study, we present results of modelling and visuali- sation of "Cycle of the Month", one of the major masterpieces of international Gothic art which is lo- cated in the Aquila tower in Buonconsiglio castle, Trento, Italy.
The paper presents the results of a test study based on 3D modelling of the “Pontonniers International high school in Strasbourg” where the Alsace Region Institution asked for building documentation in order to proceed to a complete diagnosis to conform to the current regulation (detection of asbestos and lead, fire safety, heating systems, electricity, accessibility, etc.) as well as to insure the future of the patrimony and among other the general maintenance of roofs and facades. The diagnosis and statements campaigns are usually based on maps and photos, which are used to locate damaged elements. However, aware of the possibilities offered by photogrammetric techniques, we found it interesting to integrate these methods in the diagnosis process. A 3D model of the buildings of the site seems essential for further analysis and studies, providing georeferenced data for the user and visualisation in order to know the state of the buildings and to planify the management of works. The link with a database describing the patrimony’s referential will be used to find existing maps, overall photos as well as zooms on details and other alphanumeric data, by browsing in the 3D model. To build a consistent geometric 3D model, we use on one side architectural information of the building, and on the other side dimensional data. Architectural knowledge based on analysis and overall documents leads the drawing of the model, without any scale in this first step. Only the shapes and the completeness of the model are aimed at this stage. To reach this goal, the Sketchup software package dedicated for designing buildings has been used. The integration of dimensional data is only done in a second
This paper reports on the rigorous testing of low cost desktop image measurement software that has recently become commercially available to the mass market. These software packages indicate the potential to produce accurate 3-dimensional data from multi-station convergent, and in some cases single, imagery. The investigation, commissioned by English Heritage, has centered on the 3D Builder, Photomodeler and Dimension software packages. The measurements have been carried out on imagery taken to the English Heritage specification on one of their sites. The results indicate that all the packages are capable of returning measurement accuracies to rival analytical photogrammetric methods when examined under 'real-world' conditions. Other limitations, such as plotting versatility, however restrict the suitability of the software for architectural applications. These packages have the potential to open up photogrammetry to new users but the dangers of treating them as black box technology are stressed.
Inverse Photogrammetry is used as a tool for visualizing projected developments or past situations within an existing environment. Usually traditional photogrammetric practice is followed with respect to data input, processing and output of inverse photogrammetric products. Since the purpose is visual inspection and overview rather than strict metric needs, fast and cheap methods for both the data to be gathered and the photogrammetric processing are favorable. The work is an attempt to meet these re- quirements by using video recording for data input and user friendly software for data processing. The importance of the final presentation of the results suggests the use of a virtual computer environment with various visualization capabilities, more advanced than the ones used for the purposes of traditional Inverse Photogrammetry.
The intention of this presentation is to propose a new point-of-view, from which a quest for innovative applications of Photogrammetry in assessment of cultural heritage can be initiated. As such, the main point rests on the presentation of new ideas, rather than on completely resolving the involved technical issues. Wölfflin's principles in for comparative examination of pieces of art and architecture, belonging to different art periods are evaluated with photogrammetric means. The "clarity" of figures is assessed with edge-enhancement and image segmentation. The perceived "depth" is assessed through virtual emboss of the images and creation of "virtual" stereo pairs. The image information is assessed through entropy calculations. The existence of "focal points" is assessed through interest-point operators and the development of an eye-gaze tracking system. Examples from Renaissance and Baroque artists are given, to prove the feasibility of the approaches.
The survey and deep knowledge of cultural heritage and of its conservation state contribute to the definition of environmental sustainability criteria since the preservation of the cultural heritage is one of the fundamental aspects of this concept. In order to monitor the conservation state of a cultural heritage, it is necessary to acquire a series of data referred to the heritage and to the environment where it is placed, by developing elaboration functions able to provide evaluation elements, thanks to the support of integrated technologies and methodologies. The diagnostic analysis constitutes a fundamental prerequisite for the elaboration of any kind of intervention of restoration in architectural, artistic and archaeological framework. The subject was the picture of Jesus Crucifixion, in the sanctuary of Cristo la Selva in Matera, on which were applied different types of data and non invasive integrated survey techniques. The knowledge and the study of the interaction environment-structure-artefact, was fundamental to evaluate the processes of degradation though the analysis conducted on the wall painting. Indeed, the environmental context around is the key to the reading of the objects conservation state. We made topographic and laser scanner surveys of the whole site for the reconstruction of the site itself and the study of the rooms and of their spatial allocation. Afterwards survey and integrated analysis techniques have been applied also on the paintings. It was attempted to apply some quick criteria for the analysis of the degradation and the evaluation of the conservation state of the
Creating of panoramic images is a common technique nowadays. The needed components are a sequence of overlapping digital images and a suitable stitching software. There are several software available for combining single images together just by few mouse clicks. They can also take care of the image distortions and adjust the radiometric differences so that the final image looks very consistent. In addition to the commercial software there are also free ones, which can be downloaded from Internet. Panoramic images are used in many different contexts. Real estate agents have on their web pages 360 degrees panoramic views of interiors of the houses for sale. Panoramic views can be found in many virtual reality and multimedia presentations, advertisements, work of arts, etc. Depending on the usage there are different requirements for the panoramic images. For a real estate agent it might be enough that the panorama is seamless and gives impressive presentation of the interior of the house. The most important thing is that the image looks impressive. But this is not always the case. If the images are used for measurement purposes the geometrical quality of the panoramic images is important. Even though panoramic images are not very often used in measurement tasks there are some cases where they might be advantageous. Sometimes, for example, the image must be taken quite far away from the object in order to see enough control points. This might reduce visible details. But using panoramic images taken closer to the object might give both enough control points and visible details. This paper concentrates on the geometrical quality of the panoramic images created from concentric image sequences. The main goal is to understand the suitability of panoramic images for photogrammetric measurements.
Commission V, WG V/2 KEY WORDS: relative orientation, wide-baseline stereo, vanishing point detection, feature-based matching, architecture ABSTRACT A major challenge in close-range photogrammetry and computer vision is the automation of model acquisition from imagery. Determining the relative position and orientation of close-range imagery is usually the first step in a procedure for modelling, assuming that the camera has been calibrated beforehand. An essential part of an orientation procedure based on image content is the establishment of correspondence between the images. The problem at hand is to find correspondence between two convergent images and their relative orientation simultaneously and automatically. In computer vision this is called the wide-baseline stereo problem. For the approach presented in this paper, a new feature-based matching procedure is designed that exploits the characteristics of the application by applying generic knowledge of the construction of the building. The procedure relies on rigorous statistical testing of constraints on the observations. The outline of the procedure is presented, as well as the results of experiments. Relative orientation was successfully detected for two images with an angle of 65 degree between the optical axes. It is shown that the procedure is robust with respect to unfavourable characteristics of the application, such as occlusions and repetitive structures in the building facades.
Documentation of cultural heritage sites can provide data and records for continuing research, analysis, monitoring, and change detection. Digital documentation allows computational analysis as well as archival recording of objects and sites. It provides a non-destructive approach to artifact or site mapping and measurement. Virtual models of cultural sites can be created from digital imagery, using widely available non-metric digital cameras and video recorders. Software, such as PhotoModeler® allows the construction of three-dimensional virtual modeling of objects, sites, and rooms by using multiple digital photographs. Methods for constructing virtual models currently require multiple photos from varying angles to provide sufficient ground control points as well as ample coverage of the site. Use of an extreme wide-angle lens camera, such as the Nikon fish eye lens, can overcome the need for numerous pictures and allows the capture of more information per image. This can speed the process of documentation while also providing more coverage. Wide-angle lenses have not been previously used due to the difficulty in registering the extreme distortion on the edges of the lenses. A project was undertaken to calibrate such a lens and to test its effectiveness in capturing images for virtual reconstruction using PhotoModeler software. The lens used was a Nikon fish-eye lens, mounted on a Nikon Coolpix camera. Two sites were selected for the test. The first was the interior of a modern building with a large three-story atrium. This site was chosen to initially calibrate the camera and lens for the software. The second site selected was the Salinas Pueblo Missions National Monument, a complex of archaeological sites used to test the effectiveness of the camera, lens, and PhotoModeler software in a cultural heritage site preservation application.
Omnidirectional video enables direct surround immersive viewing of a scene by warping the original image into the correct perspective given a viewing direction. However, novel views from viewpoints off the camera path can only be obtained if we solve the three-dimensional motion and calibration problem. In this paper we address the case of a parabolic catadioptric camera – a paraboloidal mirror in front of an orthographic lens – and we introduce a new representation, called the circle space, for points and lines in such images. In this circle space, we formulate an epipolar constraint involving a 44 fundamental matrix. We prove that the intrinsic parameters can be inferred in closed form from the two-dimensional subspace of the new fundamental matrix from two views if they are constant or from three views if they vary. Three-dimensional motion and structure can then be estimated from the decomposition of the fundamental matrix.
Airborne laser scanning (ALS) is a potential tool for recognising and measuring topographic earthwork features in wooded areas. To explore its potential for archaeological reconnaissance in a densely forested area, a test scan covering an Iron Age hillfort in the eastern part of Austria was carried out during the first phase of a research project.ALS sensors can penetrate vegetation canopies allowing the underlying terrain elevation to be accurately modelled. The latest generation of airborne laser scanners was used in the project. This sensor digitally records the entire waveform of the received laser echoes. We argue that the digital terrain model (DTM) generated from entire waveform ALS data could be classified with greater confidence providing a more accurate DTM than with previous ALS devices. The processing algorithms used to create the interpretative DTM are discussed in detail.Using the described procedures it was possible to remove most of the forest canopy and understorey (brushwood and low level vegetation) covering the archaeological features. The ALS DTM was compared with a detailed topographic mapping of the visible archaeological traces collected by a terrestrial survey. Significantly, very low earthwork features, which were not recognized by the trained surveyors in the field, were identified in the ALS-derived DTM. Therefore, in this study area ALS has been demonstrated as an important tool for systematic archaeological prospection in vegetated areas. There are, however, some restrictions, which are discussed in the paper.
Coded structured light is considered one of the most reliable techniques for recovering the surface of objects. This technique is based on projecting a light pattern and viewing the illuminated scene from one or more points of view. Since the pattern is coded, correspondences between image points and points of the projected pattern can be easily found. The decoded points can be triangulated and 3D information is obtained. We present an overview of the existing techniques, as well as a new and definitive classification of patterns for structured light sensors. We have implemented a set of representative techniques in this field and present some comparative results. The advantages and constraints of the different patterns are also discussed.
We describe a shape from texture method that constructs a maximum a posteriori estimate of surface coefficients using only
the deformation of individual texture elements. Our method does not need to use either the boundary of the observed surface
or any assumption about the overall distribution of elements. The method assumes that texture elements are of a limited number
of types of fixed shape. We show that, with this assumption and assuming generic view and texture, each texture element yields
the surface gradient unique up to a two-fold ambiguity. Furthermore, texture elements that are not from one of the types can
be identified and ignored. An EM-like procedure yields a surface reconstruction from the data. The method is defined for othographic
views — an extension to perspective views appears to be complex, but possible. Examples of reconstructions for synthetic images
of surfaces are provided, and compared with ground truth. We also provide examples of reconstructions for images of real scenes.
We show that our method for recovering local texture imaging transformations can be used to retexture objects in images of
real scenes.
In recent years, high-resolution recording of heritage sites has stimulated a lot of research in fields like photogrammetry, computer vision, and computer graphics. Numerous algorithms and methodologies have been proposed in the literature. In practice, what a 3D photographer needs is a commercially available solution to this so-called as-built documentation. In this paper, we present an effective approach for photo-realistic 3D model building from the combination of photogrammetry and 3D range data. The method is applied to the virtualization of a Byzantine Crypt where geometrically correct texture mapping is essential to render the environment accurately in order to produce enticing virtual visits, apply virtual restoration techniques on the frescoes and remove architectural elements that have been added over the years so that the site can then be viewed in the correct historical context. A movie entitled "CARPINIANA" was created in order to demonstrate the results.
Architectural photogrammetry has been practised for more than a century for the documentation of cultural heritage. Nowadays, the emphasis is on the construction of computer models for virtual reality applications. Since the introduction of the computer, and later the digital camera, research in photogrammetry aims at automation. This thesis reports on research on automation in architectural photogrammetry for efficient reconstruction of detailed building models from one or more, possibly widely separated, digital close-range images. This research lies on the fringes of photogrammetry and computer vision. It treats topics frequently studied in computer vision in a photogrammetric way and offers new solutions. Examples cover interior orientation and reconstruction from a single mage, vanishing point detection, and the wide-baseline stereo problem. A semi-automatic approach is chosen that exploits knowledge of the object shape, such as planarity of facades, rectangular and repeating structures in the building, and shape symmetries. Automatically or manually extracted straight image line features are the main observations in the line-photogrammetric approaches presented in this thesis. Furthermore, the methods developed are characterised by the use of robust direct solutions for approximate value computation, followed by least-squares adjustment in which the knowledge of the shape of the building is processed together with the image line observations. This integral adjustment provides optimal estimates for the object model parameters and facilitates quality assessment.