3d modelling of archaeological small finds by a low-cost range camera. Methodology and first results

The production of reliable documentation of small finds is a crucial process during archaeological excavations. Range cameras can be a valid alternative to traditional illustration methods: they are veritable 3D scanners able to easily collect the 3D geometry (shape and dimensions in metric units) of an object/scene practically in real-time. This work investigates precisely the potentialities of a promising low-cost range camera, the Structure SensorTM by Occipital, for rapid modelling archaeological objects. The accuracy assessment was thus performed by comparing the 3D model of a Cipriot-Phoenician globular jug captured by this device with the 3D model of the same object obtained through photogrammetry. In general, the performed analysis shows that Structure Sensor is capable to acquire the 3D geometry of a small object with an accuracy comparable at millimeter level to that obtainable with the photogrammetric method, even though the finer details are not always correctly modelled. The texture reconstruction is instead less accurate. In the end, it can be concluded that the range camera used for this work, due to its low-cost and flexibility, is a suitable tool for the rapid documentation of archaeological small finds, especially when not expert users are involved

From pixel to mesh: accurate and straightforward 3D documentation of cultural heritage from the Cres/Lošinj archipelago

Most people like 3D visualizations. Whether it is in movies, holograms or games, 3D (literally) adds an extra dimension to conventional pictures. However, 3D data and their visualizations can also have scientic archaeological benets: they are crucial in removing relief distortions from photographs, facilitate the interpretation of an object or just support the aspiration to document archaeology as exhaustively as possible. Since archaeology is essentially a spatial discipline, the recording of the spatial data component is in most cases of the utmost importance to perform scientic archaeological research. For complex sites and precious artefacts, this can be a di€cult, time-consuming and very expensive operation. In this contribution, it is shown how a straightforward and cost-eective hard- and software combination is used to accurately document and inventory some of the cultural heritage of the Cres/Lošinj archipelago in three or four dimensions. First, standard photographs are acquired from the site or object under study. Secondly, the resulting image collection is processed with some recent advances in computer technology and so-called Structure from Motion (SfM) algorithms, which are known for their ability to reconstruct a sparse point cloud of scenes that were imaged by a series of overlapping photographs. When complemented by multi-view stereo matching algorithms, detailed 3D models can be built from such photo collections in a fully automated way. Moreover, the software packages implementing these tools are available for free or at very low-cost. Using a mixture of archaeological case studies, it will be shown that those computer vision applications produce excellent results from archaeological imagery with little eort needed. Besides serving the purpose of a pleasing 3D visualization for virtual display or publications, the 3D output additionally allows to extract accurate metric information about the archaeology under study (from single artefacts to entire landscapes)

Virtual 3D Reconstruction of Archaeological Pottery Using Coarse Registration

The 3D reconstruction of objects has not only improved visualisation of digitised objects, it has helped researchers to actively carry out archaeological pottery. Reconstructing pottery is significant in archaeology but is challenging task among practitioners. For one, excavated potteries are hardly complete to provide exhaustive and useful information, hence archaeologists attempt to reconstruct them with available tools and methods. It is also challenging to apply existing reconstruction approaches in archaeological documentation. This limitation makes it difficult to carry out studies within a reasonable time. Hence, interest has shifted to developing new ways of reconstructing archaeological artefacts with new techniques and algorithms. Therefore, this study focuses on providing interventions that will ease the challenges encountered in reconstructing archaeological pottery. It applies a data acquisition approach that uses a 3D laser scanner to acquire point cloud data that clearly show the geometric and radiometric properties of the object’s surface. The acquired data is processed to remove noise and outliers before undergoing a coarse-to-fine registration strategy which involves detecting and extracting keypoints from the point clouds and estimating descriptions with them. Additionally, correspondences are estimated between point pairs, leading to a pairwise and global registration of the acquired point clouds. The peculiarity of the approach of this thesis is in its flexibility due to the peculiar nature of the data acquired. This improves the efficiency, robustness and accuracy of the approach. The approach and findings show that the use of real 3D dataset can attain good results when used with right tools. High resolution lenses and accurate calibration help to give accurate results. While the registration accuracy attained in the study lies between 0.08 and 0.14 mean squared error for the data used, further studies will validate this result. The results obtained are nonetheless useful for further studies in 3D pottery reassembly

Trying to break new ground in aerial archaeology

Aerial reconnaissance continues to be a vital tool for landscape-oriented archaeological research. Although a variety of remote sensing platforms operate within the earth’s atmosphere, the majority of aerial archaeological information is still derived from oblique photographs collected during observer-directed reconnaissance flights, a prospection approach which has dominated archaeological aerial survey for the past century. The resulting highly biased imagery is generally catalogued in sub-optimal (spatial) databases, if at all, after which a small selection of images is orthorectified and interpreted. For decades, this has been the standard approach. Although many innovations, including digital cameras, inertial units, photogrammetry and computer vision algorithms, geographic(al) information systems and computing power have emerged, their potential has not yet been fully exploited in order to re-invent and highly optimise this crucial branch of landscape archaeology. The authors argue that a fundamental change is needed to transform the way aerial archaeologists approach data acquisition and image processing. By addressing the very core concepts of geographically biased aerial archaeological photographs and proposing new imaging technologies, data handling methods and processing procedures, this paper gives a personal opinion on how the methodological components of aerial archaeology, and specifically aerial archaeological photography, should evolve during the next decade if developing a more reliable record of our past is to be our central aim. In this paper, a possible practical solution is illustrated by outlining a turnkey aerial prospection system for total coverage survey together with a semi-automated back-end pipeline that takes care of photograph correction and image enhancement as well as the management and interpretative mapping of the resulting data products. In this way, the proposed system addresses one of many bias issues in archaeological research: the bias we impart to the visual record as a result of selective coverage. While the total coverage approach outlined here may not altogether eliminate survey bias, it can vastly increase the amount of useful information captured during a single reconnaissance flight while mitigating the discriminating effects of observer-based, on-the-fly target selection. Furthermore, the information contained in this paper should make it clear that with current technology it is feasible to do so. This can radically alter the basis for aerial prospection and move landscape archaeology forward, beyond the inherently biased patterns that are currently created by airborne archaeological prospection

As-Built 3D Heritage City Modelling to Support Numerical Structural Analysis: Application to the Assessment of an Archaeological Remain

Terrestrial laser scanning is a widely used technology to digitise archaeological, architectural and cultural heritage. This allows for modelling the assets’ real condition in comparison with traditional data acquisition methods. This paper, based on the case study of the basilica in the Baelo Claudia archaeological ensemble (Tarifa, Spain), justifies the need of accurate heritage modelling against excessively simplified approaches in order to support structural safety analysis. To do this, after validating the 3Dmeshing process frompoint cloud data, the semi-automatic digital reconstitution of the basilica columns is performed. Next, a geometric analysis is conducted to calculate the structural alterations of the columns. In order to determine the structural performance, focusing both on the accuracy and suitability of the geometric models, static and modal analyses are carried out by means of the finite element method (FEM) on three different models for the most unfavourable column in terms of structural damage: (1) as-built (2) simplified and (3) ideal model without deformations. Finally, the outcomes show that the as-built modelling enhances the conservation status analysis of the 3D heritage city (in terms of realistic compliance factor values), although further automation still needs to be implemented in the modelling process

Aplicaciones de técnicas de imágenes 3D de bajo costo para documentación de bienes culturales

3D image recording has reached an increasing impact on the field of cultural heritage. Applications include documentation of the state of conservation and dimensions of an object, the archaeological survey of artefacts, the dissemination of museum collections and sites, and packaging designing, among others. The 3D image acquisition techniques most commonly used are laser or structured light scanning and, increasingly, close range digital photogrammetry. In this work a 3D digitization case-study is presented in order to explore the advantages and possibilities of close range digital photogrammetry respect to scanning techniques in documentation of heritage objects. Free and low-cost software used by these techniques were tested and the quality of the results obtained in each case is analyzed. The potentiality of close range digital photogrammetry to enhance the resolution of the 3D recording is also discussed.El registro de imágenes 3D ha tenido un impacto creciente en el campo de los bienes culturales. Las aplicaciones incluyen la documentación del estado de conservación y de las dimensiones de un objeto, el estudio arqueológico de artefactos, la difusión de las colecciones de museos y sitios y el diseño de embalaje, entre otros. Las técnicas de adquisición de imágenes 3D comúnmente más usadas son el escaneo con láser y con luz estructurada y, cada vez más, la fotogrametría digital de objeto cercano. En este trabajo, se presenta un estudio de caso de digitalización 3D para explorar las ventajas y posibilidades de la fotogrametría digital de objeto cercano respecto a las técnicas de escaneo en documentación de bienes culturales. Se probaron software gratuitos y de bajo costo y se analizó la calidad de los resultados obtenidos en cada caso. También se discute la potencialidad de la fotogrametría digital de objeto cercano para optimizar la resolución.Centro de Investigaciones Óptica

Close range mini Uavs photogrammetry for architecture survey

The survey of historical façades contains several bottlenecks, mainly related to the geometrical structure, the decorative framework, the presence of natural or artificial obstacles, the environment limitations. Urban context presents additional restrictions, binding by ground acquisition activity and leading to building data loss. The integration of TLS and close-range photogrammetry allows to go over such stuff, not overcoming the shadows effect due to the ground point of view. In the last year the massive use of UAVs in survey activity has permitted to enlarge survey capabilities, reaching a deeper knowledge in the architecture analysis. In the meanwhile, several behaviour rules have been introduced in different countries, regulating the UAVs use in different field, strongly restricting their application in urban areas. Recently very small and light platforms have been presented, which can partially overcome these rules restrictions, opening to very interesting future scenarios. This article presents the application of one of these very small RPAS (less than 300 g), equipped with a low-cost camera, in a close range photogrammetric survey of an historical building façade in Bologna (Italy). The suggested analysis tries to point out the system accuracy and details acquisition capacity. The final aim of the paper is to validate the application of this new platform in an architectonic survey pipeline, widening the future application of close-range photogrammetry in the architecture acquisition process

Aplicaciones de técnicas de imágenes 3D de bajo costo para documentación de bienes culturales

3D image recording has reached an increasing impact on the field of cultural heritage. Applications include documentation of the state of conservation and dimensions of an object, the archaeological survey of artefacts, the dissemination of museum collections and sites, and packaging designing, among others. The 3D image acquisition techniques most commonly used are laser or structured light scanning and, increasingly, close range digital photogrammetry. In this work a 3D digitization case-study is presented in order to explore the advantages and possibilities of close range digital photogrammetry respect to scanning techniques in documentation of heritage objects. Free and low-cost software used by these techniques were tested and the quality of the results obtained in each case is analyzed. The potentiality of close range digital photogrammetry to enhance the resolution of the 3D recording is also discussed.El registro de imágenes 3D ha tenido un impacto creciente en el campo de los bienes culturales. Las aplicaciones incluyen la documentación del estado de conservación y de las dimensiones de un objeto, el estudio arqueológico de artefactos, la difusión de las colecciones de museos y sitios y el diseño de embalaje, entre otros. Las técnicas de adquisición de imágenes 3D comúnmente más usadas son el escaneo con láser y con luz estructurada y, cada vez más, la fotogrametría digital de objeto cercano. En este trabajo, se presenta un estudio de caso de digitalización 3D para explorar las ventajas y posibilidades de la fotogrametría digital de objeto cercano respecto a las técnicas de escaneo en documentación de bienes culturales. Se probaron software gratuitos y de bajo costo y se analizó la calidad de los resultados obtenidos en cada caso. También se discute la potencialidad de la fotogrametría digital de objeto cercano para optimizar la resolución.Centro de Investigaciones Óptica

Aplicaciones de técnicas de imágenes 3D de bajo costo para documentación de bienes culturales

3D image recording has reached an increasing impact on the field of cultural heritage. Applications include documentation of the state of conservation and dimensions of an object, the archaeological survey of artefacts, the dissemination of museum collections and sites, and packaging designing, among others. The 3D image acquisition techniques most commonly used are laser or structured light scanning and, increasingly, close range digital photogrammetry. In this work a 3D digitization case-study is presented in order to explore the advantages and possibilities of close range digital photogrammetry respect to scanning techniques in documentation of heritage objects. Free and low-cost software used by these techniques were tested and the quality of the results obtained in each case is analyzed. The potentiality of close range digital photogrammetry to enhance the resolution of the 3D recording is also discussed.El registro de imágenes 3D ha tenido un impacto creciente en el campo de los bienes culturales. Las aplicaciones incluyen la documentación del estado de conservación y de las dimensiones de un objeto, el estudio arqueológico de artefactos, la difusión de las colecciones de museos y sitios y el diseño de embalaje, entre otros. Las técnicas de adquisición de imágenes 3D comúnmente más usadas son el escaneo con láser y con luz estructurada y, cada vez más, la fotogrametría digital de objeto cercano. En este trabajo, se presenta un estudio de caso de digitalización 3D para explorar las ventajas y posibilidades de la fotogrametría digital de objeto cercano respecto a las técnicas de escaneo en documentación de bienes culturales. Se probaron software gratuitos y de bajo costo y se analizó la calidad de los resultados obtenidos en cada caso. También se discute la potencialidad de la fotogrametría digital de objeto cercano para optimizar la resolución.Centro de Investigaciones Óptica