IMEKO Event Proceedings

Page 5 of 855 Results 41 - 50 of 8545

M. Mongelli, I. Bellagamba, G. Bracco, S. Migliori, A. Perozziello, S. Pierattini, A. Quintiliani, B. Mazzei
3D photogrammetric reconstruction by "Structure from Motion" as a monitoring technique for safety, conservation and improvement of the fruition of cultural heritage

In the last years, with the large growth of new state-of-the-art technologies used in the field of cultural heritage, it's increasingly necessary to promote non-invasive and non-destructive techniques which are "sensitive" to the nature of the site in which they are applied, respecting the Italian historical artistic heritage. Within the COBRA project [1], ENEA developed a new low-cost and non-destructive survey technique by 3D Photogrammetric reconstruction, using the Structure from Motion (SfM) method, for innovative applications in the field of cultural heritage [2]. This paper shows an application of this methodology on the archaeological complex of Priscilla's Catacombs in Rome. Three case studies have been identified, with several design purposes, showing the different applications of this technique: a sarcophagus called "Sarcofago delle Muse" , a chapel named "Cappella Greca" and a masonry element, which are all situated in the "Criptoportico" area.

Domenico Sguerso, Annalisa Azzola, Carlo Nike Bianchi, Bianca Federici, Sara Gagliolo, Carla Morri, Monica Montefalcone
3D photogrammetric surveys on coral reefs in the Maldives

The global increase in seawater temperature is causing irreparable damages to coral reefs all over the world. Frequency of coral bleaching episodes and mass mortality is increasing and coral reefs have not enough time to recover after these impacts. The present study concerns this phenomenon in the context of the Maldives. In this scenario, monitoring activities are very important to check the health of coral reefs, and the adoption of specific parameters such as reef rugosity and accretion of corals provides important measures of the ability of reefs to recover after bleaching. Moreover, the use of photogrammetry allows speeding up the on-site measurements, enlarging the scale and the reliability. The input data are the images traditionally taken by operators for visual analysis, paying attention to the achievement of photogrammetric principles.

V. Bagnolo, R. Argiolas
3D procedural modeling of complex vaulted systems: geometric rules vs SfM based modeling

Starting from the geometric genesis of simple and complex vaulted systems, the paper proposes a workflow developing an algorithmic model for the construction of 3D digital surface model of some vaulted systems. The writing of an algorithm allows us to obtain pavilion and cross vaults digital surface models. To test the effectiveness of the models obtained in the application of the algorithms to real case studies, the ongoing phase of the research involved the survey of some complex vaulted systems based on Light Detection And Raging (LiDAR) and Structure from Motion (SfM) techniques. The models obtained by entering the data derived from the survey in the algorithm, allow a comparison between the model derived from dense matching techniques and the algorithmic model. In particular, the results obtained from the analysis of a cross vault system present in a side gothic chapel of the church of Santa Lucia in Cagliari are presented.

De Giorgi L., Leucci G.
3D resistivity anomaly probability tomography at the archaeological site of Sagalassos (Turkey)

The archaeological site of Sagalassos is a very important settlement located in a magnificent mountain landscape, 7 km north from a little village named Aglasun (province of Burdur, SW Turkey). Since 1990 the University of Leuven (Belgium) carry out an interdisciplinary archaeological research programme that study the uninterrupted occupation of more than 1000 years in all its aspects from daily life to architecture, from trade and its mechanisms to environmental conditions of the past. The ancient roman city is a site covered under erosion layers and preserved many secrets that need to be revealed. A geophysical campaign was planned along the south facing terraces of the mountain slopes, in order to highlighting the structure of the city still covered. Site conditions (high slope, high grass, several obstacles) and the need to investigate high depths led to the choice of the most suitable geophysical methods. Particularly a 3D distribution in the subsoil of resistivity tensor probability was esteemed.

K. Tsujioka, H. Furuhashi, Y. Uchida
3D SHAPES MEASUREMENT SYSTEM USING AN OPTICAL MODULATOR

We have continued research on 3D shapes measurement system using spatial modulator. The advantages of this system are non-contact, non-invasive, and short time measurement. We proposed a method using differentiation to expand the measurable area and improve the accuracy of measurement. Additionally, We proposed to eliminate the influence of marking on target object surface. It was a very practical and effective method.

F. Bitte, H. Mischo, T. Pfeifer, G. Frankowski
3D SURFACE INSPECTION WITH A DMD BASED SENSOR

In this paper a method for non-contact scanning of small structures is presented similar to that of confocal microscopy but using the technology of Digital Micromirror Devices (DMD) instead of ordinary pinholes. It offers parallel scanning of various specimen following to a principle, where a DMD is used for illumination and a selective CCD for detection. The fundamental concepts concerning system layout and system performance as well as measurement results with a first experimental demonstrator are presented.

Ji Qi, Yingzhong Tian, Wenjun Zhang, Albert Weckenmann, Minglun Fang
3D SURFACE MICRO TOPOGRAPHY RECOVERY FROM MULTI-FOCUS IMAGES USING MODIFIED LAPLACIAN OPERATOR

Optical microscopy enables the observation of highly magnified objects and material structures on micro surfaces, however with the weakness that it can only acquire 2D images. In order to observe the areal features more accurately and intuitively, 3D surface micro topography recovery is applied to form a 3D surface model of an object from its 2D image sequence. Optical microscope has a limited depth of focus in large magnification, which makes the area within the depth of focus cleared and other area blurred. So this paper firstly acquires image sequence which obtains all useful information in one view by vertical scanning of the microscope. Secondly, each image is calculated by an appropriate focus measure operator to find the maximum focus measure value and form a 2D fused image. Then the maximum value of each pixel is accurately transferred into a distance value, forming a discrete depth map. After conducting interpolation, fitting and color mapping, a smooth and authentic 3D color model of the measured surface is obtained. Various focus measure operators such as grey level variance are used to compare their performances in 3D model recovery. The superiority of the modified Laplacian operator proposed in this paper is proved by experimenting on measured objects with different micro topography features such as ditch shaped and slope shaped structure. In addition, surface roughness information of Ra and Rz is extracted from the formed 3D models.

Antonis Antonopoulos, Sofia Antonopoulou
3D survey and BIM-ready modelling of a Greek Orthodox Church in Athens

This paper explores the application of two widely-used digital technologies, Structure-from-Motion (SfM) photogrammetry and Building Information Modelling (BIM), in the case of Byzantine ecclesiastical architecture. SfM photogrammetry was used for the 3D documentation of Agioi Anargyroi Greek Orthodox church in Athens, including exterior and internal spaces, using a combination of ground-based and aerial (UAVmounted) photography under rigorous survey control. The resulting point cloud dataset constitutes the primary survey record of the building in its current state (as-existing). Finally, a BIM-ready model of the existing structure was proposed as an alternative method for the production of coordinated 2D drawings and facilitating requirements of subsequent development of the project.

Thomas G. Mathia, Etienne Leprat, Serge Carras, Philippe Carval
3D topography measurements and characterizations of soft, living, flexible and deformable surfaces

One of the great difficulties to day in quality control and metrological highly fidelity characterisations is the case of soft and easy deformable surfaces like living bodies with history of morphology recorded (originally vegetal, animal, humane, etc) and “memory” materials like papers, human skin, varnishes, leathers, textiles, and others. one of the authors are involved since 1970’s with 3d roughness metrology, sensors, scanning components and driving systems, tactile, capacitive pneumatically assisted and optical measurement techniques. Dealing with surface texture characterisations and efforts of theirs standardisations some fundamental results will be presented and analytically evaluated. Dimensional measurements in manufacturing, metrology software and the comparing evaluation, as well as uncertainty, tolerance, testing, calibration and testing methods and total quality management constitutes essential problem. Critical analysis of different methods in domain of 3d texture characterisations is not reported commenting advantages and week points in context of quality control due to limited space in this paper. Some case studies in terms of education will be presented.

J. Escande, P. Gajan, A. Strzelecki
3D VELOCITY PROFILE RECONSTRUCTION OF GAS FLOW IN A PIPE WITH ULTRASONIC TOMOGRAPHY

Beyond possibilities of simple flowmeters, ultrasonic tomography allows to reconstitute the three-dimensional velocity field over a circular pipe cross section. The differences of transit times between transducers distributed around the pipe are used in an iterative algebraic reconstruction algorithm in order to reconstruct the three velocity components. This experimental method has been tested successfully to quantify the 3D velocity field of various flows (fully developed, asymmetric and swirling air flows).

Page 5 of 855 Results 41 - 50 of 8545