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Multi-dimensional and multi-temporal motion estimation of a beam surface during dynamic testing using low-frame rate digital cameras / I. Detchev in Applied geomatics, vol 9 n° 3 (September 2017)  

Public [article]  inApplied geomatics > vol 9 n° 3 (September 2017) . - pp 127 - 141 Titre : Multi-dimensional and multi-temporal motion estimation of a beam surface during dynamic testing using low-frame rate digital cameras Type de document : Article/Communication Auteurs : I. Detchev, Auteur ; Derek Litchi, Auteur ; Ayman Habib, Auteur ; Mamdouh El-Badry, Auteur Année de publication : 2017 Article en page(s) : pp 127 - 141 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Photogrammétrie numérique [Termes IGN] ajustement de paramètres [Termes IGN] caméra numérique [Termes IGN] déviation de la verticale [Termes IGN] méthode des moindres carrés [Termes IGN] photogrammétrie métrologique Résumé : (Auteur) The combination of digital close-range photogrammetric systems and image processing techniques has been employed in structural health monitoring applications for more than 10 years. The use of off-the-shelf entry level digital single-lens reflex cameras has lately become a suitable choice even for applications requiring sub-millimetre- level precision especially when the involved devices need to be inexpensive. The drawback of such low-cost cameras is in the trade-off between spatial resolution, frame rate, and burst rate—at the highest available spatial resolution, a high frame rate is either not possible or it has a low burst rate. This may be problematic when monitoring a structural component during a dynamic/fatigue test. In order to estimate specimen motion in such a situation, this paper proposes an innovative sinusoidal fitting based on a least squares adjustment. This method simultaneously processes multiple bursts of data in order to synthetically increase the sampling frequency of the system. The input data for the adjustment comes from a full surface modelling procedure based on a newly proposed generalized 3D polynomial. The experimental results include a beam deformation test performed in a structures laboratory. The new sinusoidal fitting method effectively increased the system temporal resolution three-fold, which improved the precision of the derived parameters with up to two orders of magnitude. The root mean square error of the residuals were as good as 26 μm, and the one of the estimated amplitudes from the photogrammetric system versus a set of laser transducers used as control was as small as 43 μm. Numéro de notice : A2017-595 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1007/s12518-017-0184-0 Date de publication en ligne : 10/04/2017 En ligne : https://doi.org/10.1007/s12518-017-0184-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86803 [article]

Image matching and surface registration for 3D reconstruction of a scoliotic torso / I. Detchev in Geomatica, vol 65 n° 2 (June 2011)  

Public [article]  inGeomatica > vol 65 n° 2 (June 2011) . - pp 175 - 187 Titre : Image matching and surface registration for 3D reconstruction of a scoliotic torso Type de document : Article/Communication Auteurs : I. Detchev, Auteur ; A. Habib, Auteur ; Y. Chang, Auteur Année de publication : 2011 Article en page(s) : pp 175 - 187 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes IGN] analyse diachronique [Termes IGN] appariement d'images [Termes IGN] étalonnage d'instrument [Termes IGN] imagerie médicale [Termes IGN] médecine humaine [Termes IGN] photogrammétrie médicale [Termes IGN] précision submillimétrique [Termes IGN] reconstruction 3D [Termes IGN] surveillance sanitaire Résumé : (Auteur) The focus of this research is a hierarchical image matching strategy and a multiple surface registration technique for 3D reconstruction of a scoliotic torso. Scoliosis is a deformity of the human spine most commonly occurring in children. After being detected, periodic examinations via x-rays are traditionally used to measure its progression. However, due to the increased risk of cancer, non-invasive and radiation-free scoliosis detection and progression monitoring methodologies are being researched. For example, quantifying the scoliotic deformity through the torso surface is a valid alternative because of its high correlation with the internal spine curvature. This work proposes a low-cost, multi-camera photogrammetric system for semi-automated 3D reconstruction of a torso surface with a sub-millimetre level accuracy. The paper first describes the system design and calibration for optimal accuracy. It then covers the reconstruction and registration procedures giving insights into the hierarchical image matching strategy and the multiple surface registration technique. Final accuracy is evaluated through the goodness of fit between the reconstructed surface and a more accurate set of points measured by a coordinate measuring machine. Numéro de notice : A2011-542 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.5623/cig2011-026 En ligne : https://doi.org/10.5623/cig2011-026 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31436 [article]

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