Documentation of heritage buildings using close-range UAV images: dense matching issues, comparison and case studies

International audienceThree-dimensional (3D) documentation of heritage buildings has long employed both image-based and range-based techniques. Unmanned aerial vehicles (UAVs) provide a particular advantage for image-based techniques in acquiring aerial views, which are difficult to attain using classical terrestrial-based methods. The technological development of optical sensors and dense matching algorithms also complement existing photogrammetric workflows for the documentation of heritage objects. In this paper, fundamental concepts in photogrammetry and 3D reconstruction based on structure from motion (SfM) will be briefly reviewed. Two case studies were performed using two types of UAVs, one being a state-of-the-art platform dedicated to obtaining close-range images. Comparisons with laser scanning data were performed and several issues regarding the aerial triangulation and dense matching results were assessed. The results show that although the dense matching of these UAV images may generate centimetre-level precision, a further increase in precision is often hampered by the quality of the onboard sensor

Validation of point clouds segmentation algorithms through their application to several case studies for indoor building modelling

International audienceLaser scanners are widely used for the modelling of existing buildings and particularly in the creation process of as-built BIM (Building Information Modelling). However, the generation of as-built BIM from point clouds involves mainly manual steps and it is consequently time consuming and error-prone. Along the path to automation, a three steps segmentation approach has been developed. This approach is composed of two phases: a segmentation into sub-spaces namely floors and rooms and a plane segmentation combined with the identification of building elements. In order to assess and validate the developed approach, different case studies are considered. Indeed, it is essential to apply algorithms to several datasets and not to develop algorithms with a unique dataset which could influence the development with its particularities. Indoor point clouds of different types of buildings will be used as input for the developed algorithms, going from an individual house of almost one hundred square meters to larger buildings of several thousand square meters. Datasets provide various space configurations and present numerous different occluding objects as for example desks, computer equipments, home furnishings and even wine barrels. For each dataset, the results will be illustrated. The analysis of the results will provide an insight into the transferability of the developed approach for the indoor modelling of several types of buildings

A LOW COST TLS BASED LAND MOBILE MAPPING SYSTEM ASSISTED BY PHOTOGRAMMETRY

This paper presents an approach of improving navigational data in mobile mapping by using additional photogrammetric measurements. Images taken during a mobile mission are considered as support of GPS/INS while the consumer grade inertial MEMS unit used in the presented mobile system provides only poor estimation of position and attitude even with GPS aid. Nevertheless, this estimation provides initial values for image processing.  Simultaneous bundle adjustment could be done easily with approximate values obtained by GPS/INS solution. The adaptation of our algorithm to meet the case of low cost land mobile mapping is also explained. The feedback to the trajectory determination is discussed from a Kalman decentralized filter point of view. Automatic tie point object coordinates approximation depending on terrestrial laser point clouds is also presented in  order to reach a global automatic data processing. The precision of the solution is discussed and assessed by comparing the resulting point clouds with more accurate data sources.

Integration of Heterogeneous Cultural Heritage Data in a Web-based <br />Information System: A Case Study from Vianden Castle, Luxembourg

ISBN 978-963-8046-90-1International audienceThe project presented here proposes the first implementation of a Web-based Information System for the conservation, handling, and use of site data. The case study is the castle of Vianden in Luxembourg, on which considerable archaeological data have accumulated over the years. There is a recognized need in archaeology for a tool that will allow for fast, effective, and flexible exploratory analysis of data, especially at spatial and temporal levels. We have developed such an Information System with maximal portability by using Extensible Markup Language (XML) and Extensible Stylesheet Language (XSL) for data exchange. Our system consists of several interfaces permitting different types of access to heterogeneous information. We propose a description of the data in textual interfaces along with images, and dynamic links to this data through interactive 2D and 3D representations. The 2D images, photos, or vectors are generated in Scalable Vector Graphics (SVG), while 3D models are generated in X3

A web information system for the management and the dissemination of Cultural Heritage data.

Safeguarding and exploiting Cultural Heritage induce the production of numerous and heterogeneous data. The management of these data is an essential task for the use and the diffusion of the information gathered on the field. Previously, the data handling was a hand-made task done thanks to efficient and experienced methods. Until the growth of computer science, other methods have been carried out for the digital preservation and treatment of Cultural Heritage information. The development of computerized data management systems to store and make use of archaeological datasets is then a significant task nowadays. Especially for sites that have been excavated and worked without computerized means, it is now necessary to put all the data produced onto computer. This allows preservation of the information digitally (in addition with the paper documents) and offers new exploitation possibilities, like the immediate connection of different kinds of data for analyses, or the digital documentation of the site for its improvement. Geographical Information Systems have proved their potentialities in this scope, but they are not always adapted to the management of features at the scale of a particular archaeological site. Therefore this paper aims to present the development of a Virtual Research Environment dedicated to the exploitation of intra-site Cultural Heritage data. The Information System produced is based on open-source software modules dedicated to the Internet, so users can avoid being software driven and can register and consult data from different computers. The system gives the opportunity to do exploratory analyses of the data, especially at spatial and temporal levels. The system is compliant to every kind of Cultural Heritage site and allows management of diverse types of data. Some experimentation has been done on sites managed by the Service of the National Sites and Monuments of Luxembourg

Olmeta-di-Capocorso – Grotta Scritta : Canaghiolo, E Fontanelle

Le site de la Grotta Scritta I se trouve sur le versant ouest du Cap Corse, sur la commune d’Olmeta-di-Capocorso, au secteur dit de E. Funtanelle (Canaghiolo). Il s’agit d’un surplomb rocheux naturel situé sur un massif schisteux, à environ 412 m d’altitude. L’auvent surplombe la plage de Nonza et fait face au golfe de Saint-Florent. Un second abri, la Grotta Scritta II, est localisé à quelques mètres en contrebas du premier site. L’opération conduite en mars 2014 correspond au relevé lasergr..

Flexible Photogrammetric Computations Using Modular Bundle Adjustment: The Chain Rule and the Collinearity Equations

International audienceThe main purpose of this paper is to show that photogrammetric bundle adjustment computations can be sequentially organized into modules. Furthermore, the chain rule can be used to simplify the computation of the analytical Jacobians needed by the adjustment. Novel projection models can be flexibly evaluated by inserting, modifying, or swapping the order of selected modules. As a proof of concept, two variants of the pin-hole projection model with Brown lens distortion were implemented in the open-source Damped Bundle Adjustment Toolbox (DBAT) and applied to simulated and calibration data for a non-conventional lens system. The results show a significant difference for the simulated, error-free, data but not for the real calibration data. The current flexible implementation incurs a performance loss. However, in cases where flexibility is more important, the modular formulation should be a useful tool to investigate novel sensors, data processing techniques, and refractive models

: THE BRONZE AGE PAINTED CAVE OF " LES FRAUX ", DORDOGNE (FRANCE)

International audienceFor six years, an interdisciplinary team of archaeologists, surveyors, environmentalists and archaeometrists have jointly carried out the study of a Bronze Age painted cave, registrered in the French Historical Monuments. The archaeological cave of Les Fraux (Saint-Martin-de-Fressengeas, Dordogne) forms a wide network of galleries, characterized by the exceptional richness of its archaeological remains such as ceramic and metal deposits, parietal representation and about domestic fireplaces. This cave is the only protohistorical site in Europe wherein are gathered testimonies of domestic, spiritual and artistic activities. Fortunately, the cave was closed at the end of the Bronze Age, following to the collapse of its entrance. The site was re-discovered in 1989 and its study started in 2007. The study in progress takes place in a new kind of tool founded by the CNRS's Institute of Ecology and Environment. The purpose of this observatory is the promotion of new methodologies and experimental studies in Global Ecology. In that framework, 3D models of the cave constitute the common work support and the best way for scientific communication for the various studies conducted on the site by nearly forty researchers. In this specific context, a partnership among archaeologists and surveyors from INSA Strasbourg allows the team to develop, in an interdisciplinary way, new methods of data acquiring based on contact-free measurements techniques in order to acquire a full 3D-documentation. This work is conducted in compliance with the integrity of the site. Different techniques based on Terrestrial Laser Scanning, Digital Photogrammetry and Spatial Imaging System have been used in order to generate a geometric and photorealistic 3D model from the combination of point clouds and photogrammetric images, for both visualization and accurate documentation purposes. Various scales of acquiring and diverse resolutions have been applied according to the subject: global volume cave, parietal representations, deposits... The aim of this paper is to issue a statement of the different 3D technologies tested in this outstanding site and the integration of magnetic measurements in the models

: Approche multiscalaire

The archaeological cave " Les Fraux " (Saint-Martin-de-Fressengeas, Dordogne) forms a great network of galleries, characterized by the exceptional richness of its archaeological Bronze age remains such as domestic fireplaces, ceramic and metal deposits, fingerings incised in the clayey-walls. The cave has been closed according to the collapse of its entrance, at the end of the Bronze Age. The study in progress takes place in a new kind of tool founded by the Institute of Ecology and Environment (INEE): sites dedicated to the study of global ecology. In that framework, we try to develop new methods of data acquiring, according to an interdisciplinary way. A partnership among archaeologists and surveyors from INSA allow the 3D recording and modelling of the global volume cave. In the same time, we implement the high resolution acquiring of parietal representations (engravings and fingerings). The aim of this paper is focusing on the complementarity of data which are produced by the different scales of 3D recording used in the cave. Another purpose is to issue a statement of the different 3D technologies tested in "Les Fraux". Finally, we propose to start a discussion about the way we try to produce a 3D documentation accurate and adapted to the researchers needs.La grotte ornée des Fraux (Saint-Martin-de-Fressengeas, Dordogne), vaste réseau de galeries ayant livré des vestiges d'une rare richesse (aménagements domestiques, dépôts de mobilier, manifestations pariétales, tous datés de l'âge du Bronze), a été scellée à la fin de l'âge du Bronze suite à l'effondrement de son porche d'entrée. L'étude du site est réalisée dans le cadre d'un SEEG de l'INEE, au sein duquel sont testées, de manière interdisciplinaire, de nouvelles méthodes d'acquisition de données. Dans ce cadre, un partenariat mis en place depuis 4 années entre archéologues et topographes de l'INSA a permis de conduire la numérisation 3D de la volumétrie totale du réseau et, en parallèle, l'acquisition en haute définition des panneaux ornés. L'objet de cet article est de mettre l'accent sur la complémentarité des données offertes par la multiplicité des échelles d'acquisition effectuées in situ, de dresser un premier bilan des différentes techniques testées dans ce cadre, et de poser les premiers jalons d'une réflexion sur la production d'une documentation adaptée aux besoins des partenaires de l'équipe de recherch