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Using optical projection in close-range photogrammetry for 6DOF sensor positioning / B. Zheng in Photogrammetric Engineering & Remote Sensing, PERS, vol 79 n° 1 (January 2013)  

Public [article]  inPhotogrammetric Engineering & Remote Sensing, PERS > vol 79 n° 1 (January 2013) . - pp 79 - 86 Titre : Using optical projection in close-range photogrammetry for 6DOF sensor positioning Type de document : Article/Communication Auteurs : B. Zheng, Auteur ; Y. Dong, Auteur ; A. Davies, Auteur ; B. Mullany, Auteur ; E. Morse, Auteur Année de publication : 2013 Article en page(s) : pp 79 - 86 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Photogrammétrie terrestre [Termes IGN] étalonnage d'instrument [Termes IGN] orientation du capteur [Termes IGN] photogrammétrie métrologique Résumé : (Auteur) A novel, low cost, non-contact, six degrees of freedom (DOF) measurement technique is proposed that enables real-time measurement of a small lightweight module's location. Straight forward applications of the proposed technique include robot calibration by installing the module to the end effector of a robot arm, and head-tracking in a typical virtual reality environment by attaching the module to a human head. The technique is based on a combination of photogrammetry and optical pattern projection. The module generates an optical pattern that is observable on the surrounding walls, and photogrammetry is used to measure the absolute coordinates of features in the projected optical pattern with respect to a defined global coordinate system. By combining these absolute coordinates with the known angular information of the optical projection beams, a minimization algorithm can be used to extract the absolute coordinates and angular orientation of the module itself. Experimental agreement of 1 to 5 parts in 103 was obtained by translating the module over 0.9 m and by rotating it through 60°. Numerical simulations were conducted to demonstrate that optimum design of the projected pattern gives a lower associated measurement uncertainty than is possible by direct photogrammetric measurement with traditional tie points. This paper documents the proof of principle and describes how the measurement can be further improved. Numéro de notice : A2013-007 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.14358/PERS.79.1.79 En ligne : https://doi.org/10.14358/PERS.79.1.79 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32145 [article]

Algorithms for constrained k-nearest neighbor queries over moving object trajectories / Yunjun Gao in Geoinformatica, vol 14 n° 2 (April 2010)  

Public [article]  inGeoinformatica > vol 14 n° 2 (April 2010) . - pp 241 - 276 Titre : Algorithms for constrained k-nearest neighbor queries over moving object trajectories Type de document : Article/Communication Auteurs : Yunjun Gao, Auteur ; B. Zheng, Auteur ; G. Chen, Auteur ; Qi Li, Auteur Année de publication : 2010 Article en page(s) : pp 241 - 276 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Bases de données localisées [Termes IGN] arbre-R [Termes IGN] base de données d'objets mobiles [Termes IGN] base de données spatiotemporelles [Termes IGN] classification barycentrique [Termes IGN] objet mobile [Termes IGN] processus spatial [Termes IGN] programmation par contraintes [Termes IGN] requête spatiale Résumé : (Auteur) An important query for spatio-temporal databases is to find nearest trajectories of moving objects. Existing work on this topic focuses on the closest trajectories in the whole data space. In this paper, we introduce and solve constrained k-nearest neighbor (CkNN) queries and historical continuous CkNN (HCCkNN) queries on R-tree-like structures storing historical information about moving object trajectories. Given a trajectory set D, a query object (point or trajectory) q, a temporal extent T, and a constrained region CR, (i) a CkNN query over trajectories retrieves from D within T, the k (? 1) trajectories that lie closest to q and intersect (or are enclosed by) CR; and (ii) an HCCkNN query on trajectories retrieves the constrained k nearest neighbors (CkNNs) of q at any time instance of T. We propose a suite of algorithms for processing CkNN queries and HCCkNN queries respectively, with different properties and advantages. In particular, we thoroughly investigate two types of CkNN queries, i.e., CkNNP and CkNNT, which are defined with respect to stationary query points and moving query trajectories, respectively; and two types of HCCkNN queries, namely, HCCkNNP and HCCkNNT, which are continuous counterparts of CkNNP and CkNNT, respectively. Our methods utilize an existing data-partitioning index for trajectory data (i.e., TB-tree) to achieve low I/O and CPU cost. Extensive experiments with both real and synthetic datasets demonstrate the performance of the proposed algorithms in terms of efficiency and scalability. Copyright Springer Numéro de notice : A2010-067 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE/INFORMATIQUE Nature : Article DOI : 10.1007/s10707-009-0084-5 Date de publication en ligne : 28/04/2009 En ligne : https://doi.org/10.1007/s10707-009-0084-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30263 [article]

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