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Object tracking with robotic total stations : current technologies and improvements based on image data / Matthias Ehrhart in Journal of applied geodesy, vol 11 n° 3 (September 2017)  

Public [article]  inJournal of applied geodesy > vol 11 n° 3 (September 2017) . - pp 131 - 142 Titre : Object tracking with robotic total stations : current technologies and improvements based on image data Type de document : Article/Communication Auteurs : Matthias Ehrhart, Auteur ; Werner Lienhart, Auteur Année de publication : 2017 Article en page(s) : pp 131 - 142 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Topographie [Termes IGN] instrumentation Leica [Termes IGN] instrumentation Topcon [Termes IGN] instrumentation Trimble [Termes IGN] positionnement par GNSS [Termes IGN] poursuite de cible [Termes IGN] prisme (optique) [Termes IGN] tachéomètre électronique robotisé [Termes IGN] vidéotachéomètre Résumé : (Auteur) The importance of automated prism tracking is increasingly triggered by the rising automation of total station measurements in machine control, monitoring and one-person operation. In this article we summarize and explain the different techniques that are used to coarsely search a prism, to precisely aim at a prism, and to identify whether the correct prism is tracked. Along with the state-of-the-art review, we discuss and experimentally evaluate possible improvements based on the image data of an additional wide-angle camera which is available for many total stations today. In cases in which the total station’s fine aiming module loses the prism, the tracked object may still be visible to the wide-angle camera because of its larger field of view. The theodolite angles towards the target can then be derived from its image coordinates which facilitates a fast reacquisition of the prism. In experimental measurements we demonstrate that our image-based approach for the coarse target search is 4 to 10-times faster than conventional approaches. Numéro de notice : A2017-568 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/jag-2016-0043 En ligne : https://doi.org/10.1515/jag-2016-0043 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86688 [article]

High frequent total station measurements for the monitoring of bridge vibrations / Werner Lienhart in Journal of applied geodesy, vol 11 n° 1 (March 2017)  

Public [article]  inJournal of applied geodesy > vol 11 n° 1 (March 2017) . - pp 1 - 8 Titre : High frequent total station measurements for the monitoring of bridge vibrations Type de document : Article/Communication Auteurs : Werner Lienhart, Auteur ; Matthias Ehrhart, Auteur ; Magdalena Grick, Auteur Année de publication : 2017 Article en page(s) : pp 1 - 8 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] pont [Termes IGN] surveillance d'ouvrage [Termes IGN] tachéomètre électronique [Termes IGN] topométrie de précision [Termes IGN] vidéotachéomètre Résumé : (Auteur) Robotic total stations (RTS) are frequently used for the measurement of temperature induced bridge deformations or during load testing of bridges. In experimental setups, total stations have also been used for the measurement of dynamic bridge deformations. However, with standard configurations the measurement rate is not constant and on average an update rate of 7–10Hz can be achieved. This is not sufficient for the vibration monitoring of bridges considering their natural frequencies which are also in the same range. In this paper, we present different approaches to overcome these problems. In the first two approaches we demonstrate how the measurement rate to prisms can be increased to 20Hz to determine vertical deformations of bridges. Critical aspects like the measurement resolution of the automated target tracking and the correct sequence of steering commands are discussed. In another approach we demonstrate how vertical bridge vibrations can be measured using an image assisted total station (IATS) and corresponding processing techniques. The advantage of image-based methods is that structural features of a bridge like bolts can be used as targets. Therefore, no expensive prisms have to be mounted and access to the bridge is not required. All approaches are verified by laboratory investigations and their suitability is proven in a field experiment on a 74m long footbridge. In this field experiment the natural frequencies derived from the total station measurements are compared to the results of accelerometer measurements. Numéro de notice : A2017-280 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1515/jag-2016-0028 En ligne : https://doi.org/10.1515/jag-2016-0028 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85313 [article]