Commission VI, WG VI/4 KEY WORDS : drone, metrology, bowl effect, drift, dyke, MicMac, 4D monitoring ABSTRACT:The photogrammetric treatment of images acquired on a linear axis is a problematic case. Such tricky configurations often leads to bended 3D models, described as a bowl effect, which requires ground measurements to be fixed. This article presents different solutions to overcome that problem. All solutions have been implemented into the free open-source photogrammetric suite MicMac. The article presents the lasts evolutions of MicMac's bundle adjustment core, as well as some extended calibration models and how they fit for the camera evaluated. The acquisition process is optimized by presenting how oblique images can improve the accuracy of the orientations, while the 3D models accuracies are assessed by producing a millimeter accurate ground truth from terrestrial photogrammetry.
With the development of unmanned aerial vehicles (UAVs) and global navigation satellite system (GNSS), the accurate camera positions at exposure can be known and the GNSS-assisted bundle block adjustment (BBA) approach is possible for integrated sensor orientation (ISO). This study employed ISO approach for camera pose determination with the objective of investigating the impact of a good sensor pre-calibration on a poor acquisition geometry. Within the presented works, several flights were conducted on a dike by a small UAV embedded with a metric camera and a GNSS receiver. The multi-lever-arm estimation within the BBA procedure makes it possible to merge image blocks of different configurations such as nadir and oblique images without physical constraints on camera and GNSS antenna positions. The merged image block achieves a better accuracy and the sensor self-calibrated well. The issued sensor calibration is then applied to a less preferable acquisition configuration and the accuracy is significantly improved. For a corridor acquisition scene of about 600 m, a centimetric accuracy is reached with one GCP. With the provided sensor pre-calibration, an accuracy of 3.9 normalcnormalm is achieved without any GCP.
ABSTRACT:Unmanned Aerial Vehicles (UAV) and photogrammetry are two fields that have been boosted these last years. Using aerial means, one can easily acquire aerial data and produce high resolution dense surface models, orthophotos,... IGN (the French Mapping Agency) and CNR (Compagnie Nationale du Rhône, which is the concessionary of the Rhône river and a hydraulic energy producer) have associated themselves on a thesis protect. The aim is to be able to monitor dykes from images acquired by UAV and take benefit from their convenience, targeting a centimetric accuracy on the Z-axis. This article presents our motivations and the problems we have faced in our first experiments. We also worked on a site covered by a terrestrial Lidar survey, and studied how minimizing the bundle adjustment residuals by using different calibrations would influence the quality of the computed models. Finally, we will introduce in a last part our last experiments to get a better understanding of poses estimation accuracy.
Abstract. Developers and operators of a full range of hydroelectricity structures (500 kms of dykes, 19 in-stream structures and 12 high-head installations) for over 100 years, CNR and SHEM are required to guarantee a constant monitoring of their infrastructure to ensure hydraulic safety, meet their regulatory requirements and to be prepared to new challenges: improved efficiencies, optimised monitoring of high risks areas and information sharing between the different operators.To reach a better surveillance and improve risk management, CNR and SHEM called upon the Advitam Group to set up, in less than 12 months, the innovative software solution 'ALOHA' for the inspections and monitoring of their structures to a better knowledge of risk.This monitoring is ensured by over 15,000 sensors, allowing an analysis of historic data spread over 30 years.ALOHA, a development based on the ScanPrint® web based software, allows the full range of operators to collect, visualise, analyse and edit all of the auscultation and monitoring data in an integrated platform. To respond to the specific needs of CNR and SHEM, innovative modules were developed for both in-office work and mobile tools. This article will detail the functional requirements of the CNR and SHEM, the solutions proposed by Advitam with the ALOHA system and the integration of the solution in the risk management. 35(6(17$7,21 2) 7+( &217(;7In the context of the advent of new technologies, in order to ensure the longevity of structures, and driven by exacting "safety" regulations, the surveillance tools for hydraulic structures need to undergo a transformation. The ALOHA project fits neatly in this scope, and within the ambition of the Engie Group.
Résumé. Pour connaître la débitance de ses barrages, la Compagnie Nationale du Rhône calcule les débits par une équation de débitance. Celle-ci est spécifique au type de vannes de l'ouvrage et est déterminée par des essais réalisés sur modèle physique au 1/35 ème . Le coefficient de débitance est modélisé pour chaque vanne par une équation unique, qui est ensuite implémentée dans l'automate de calcul du débit de l'ouvrage. L'objectif de l'étude est de quantifier les incertitudes associées au débit calculé sur l'ouvrage et de hiérarchiser les composantes d'incertitude afin d'identifier les améliorations à engager. L'estimation de l'incertitude est réalisée par application de la loi de composition des incertitudes-types et comparée aux résultats des propagations des densités de probabilité par simulations de Monte-Carlo. Le domaine d'intérêt comprend de multiples valeurs des variables principales (hauteurs d'eau en amont et en aval, ouverture de la vanne, etc.), avec quatre régimes d'écoulement. Pour 92,5 % des 50 000 configurations traitées, l'écart entre les deux méthodes est inférieur à 1 % ; les autres configurations, présentant des écarts plus importants, correspondent à un régime d'écoulement particulier dont l'équation est fortement non linéaire. L'étude montre les spécificités et difficultés de l'estimation des incertitudes par les méthodes de composition des incertitudes-types et par Monte-Carlo pour un domaine d'intérêt étendu, tant au niveau des calculs qu'au niveau de l'interprétation des résultats.
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