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Combinatorial optimization applied to VLBI scheduling / A. Corbin in Journal of geodesy, vol 94 n°2 (February 2020)  

Public [article]  inJournal of geodesy > vol 94 n°2 (February 2020) Titre : Combinatorial optimization applied to VLBI scheduling Type de document : Article/Communication Auteurs : A. Corbin, Auteur ; B. Niedermann, Auteur ; Axel Nothnagel, Auteur ; et al., Auteur Année de publication : 2020 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] analyse combinatoire (maths) [Termes descripteurs IGN] données VGOS [Termes descripteurs IGN] interférométrie à très grande base [Termes descripteurs IGN] positionnement par ITGB [Termes descripteurs IGN] programmation linéaire [Termes descripteurs IGN] retard troposphérique zénithal [Termes descripteurs IGN] station VLBI [Termes descripteurs IGN] téléscope [Termes descripteurs IGN] temps universel coordonné Résumé : (auteur) Due to the advent of powerful solvers, today linear programming has seen many applications in production and routing. In this publication, we present mixed-integer linear programming as applied to scheduling geodetic very-long-baseline interferometry (VLBI) observations. The approach uses combinatorial optimization and formulates the scheduling task as a mixed-integer linear program. Within this new method, the schedule is considered as an entity containing all possible observations of an observing session at the same time, leading to a global optimum. In our example, the optimum is found by maximizing the sky coverage score. The sky coverage score is computed by a hierarchical partitioning of the local sky above each telescope into a number of cells. Each cell including at least one observation adds a certain gain to the score. The method is computationally expensive and this publication may be ahead of its time for large networks and large numbers of VLBI observations. However, considering that developments of solvers for combinatorial optimization are progressing rapidly and that computers increase in performance, the usefulness of this approach may come up again in some distant future. Nevertheless, readers may be prompted to look into these optimization methods already today seeing that they are available also in the geodetic literature. The validity of the concept and the applicability of the logic are demonstrated by evaluating test schedules for five 1-h, single-baseline Intensive VLBI sessions. Compared to schedules that were produced with the scheduling software sked, the number of observations per session is increased on average by three observations and the simulated precision of UT1-UTC is improved in four out of five cases (6 μs average improvement in quadrature). Moreover, a simplified and thus much faster version of the mixed-integer linear program has been developed for modern VLBI Global Observing System telescopes. Numéro de notice : A2020-153 Thématique : MATHEMATIQUE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-020-01348-w date de publication en ligne : 29/01/2020 En ligne : https://doi.org/10.1007/s00190-020-01348-w Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=94786 [article]

Spatiotemporal model for assessing the stability of urban human convergence and divergence patterns / Zhixiang Fang in International journal of geographical information science IJGIS, vol 31 n° 11-12 (November - December 2017)  

Public [article]  inInternational journal of geographical information science IJGIS > vol 31 n° 11-12 (November - December 2017) . - pp 2119 - 2141 Titre : Spatiotemporal model for assessing the stability of urban human convergence and divergence patterns Type de document : Article/Communication Auteurs : Zhixiang Fang, Auteur ; Xiping Yang, Auteur ; Yang Xu, Auteur ; et al., Auteur Année de publication : 2017 Article en page(s) : pp 2119 - 2141 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale [Termes descripteurs IGN] analyse combinatoire (maths) [Termes descripteurs IGN] analyse spatio-temporelle [Termes descripteurs IGN] échelle variable [Termes descripteurs IGN] géopositionnement [Termes descripteurs IGN] Kouangtoung (Chine) [Termes descripteurs IGN] mobilité urbaine [Termes descripteurs IGN] réseau de transport [Termes descripteurs IGN] téléphonie mobile [Termes descripteurs IGN] trace GPS [Termes descripteurs IGN] transport collectif Résumé : (Auteur) Understanding the stability of urban flows is critical for urban transportation, urban planning and public health. However, few studies have measured the stability of aggregate human convergence or divergence patterns. We propose a spatiotemporal model for assessing the stability of human convergence and divergence patterns. A mobile phone location data set obtained from Shenzhen, China, was used to assess the stability of daily human convergence and divergence patterns at three different spatial scales, i.e. points (cell phone towers), lines (bus lines) and areas (traffic analysis zones [TAZs]). Our analysis results demonstrated that the proposed model can identify points and bus lines with time-dependent variations in stability, which is useful for delineating TAZs for transportation planning, or adjusting bus timetables and routes to meet the needs of bus riders. Comparisons of the results obtained from the proposed model and the widely used entropy measure indicated that the proposed model is suitable for assessing the differences in stability for various types of spatial analysis units, e.g. cell phone towers. Therefore, the proposed model is a useful alternative approach of measuring spatiotemporal stability of aggregate human convergence and divergence patterns, which can be derived from the space–time trajectories of moving objects. Numéro de notice : A2017-698 Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/13658816.2017.1346256 En ligne : https://doi.org/10.1080/13658816.2017.1346256 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=88079 [article]

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Snapshot and continuous points-based trajectory search / Shuyao Qi in Geoinformatica [en ligne], vol 21 n° 4 (October - December 2017)  

Public [article]  inGeoinformatica [en ligne] > vol 21 n° 4 (October - December 2017) . - pp 669 - 701 Titre : Snapshot and continuous points-based trajectory search Type de document : Article/Communication Auteurs : Shuyao Qi, Auteur ; Dimitri Sacharidis, Auteur ; Panagiotis Bouros, Auteur ; Nikos Mamoulis, Auteur Année de publication : 2017 Article en page(s) : pp 669 - 701 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse spatiale [Termes descripteurs IGN] analyse combinatoire (maths) [Termes descripteurs IGN] calcul d'itinéraire [Termes descripteurs IGN] distance [Termes descripteurs IGN] itinéraire voisin le plus proche [Termes descripteurs IGN] temps [Termes descripteurs IGN] temps instantané [Termes descripteurs IGN] théorie des possibilités Résumé : (Auteur) Trajectory data capture the traveling history of moving objects such as people or vehicles. With the proliferation of GPS and tracking technologies, huge volumes of trajectories are rapidly generated and collected. Under this, applications such as route recommendation and traveling behavior mining call for efficient trajectory retrieval. In this paper, we first focus on distance-to-points trajectory search; given a collection of trajectories and a set query points, the goal is to retrieve the top-k trajectories that pass as close as possible to all query points. We advance the state-of-the-art by combining existing approaches to a hybrid nearest neighbor-based method while also proposing an alternative, more efficient spatial range-based approach. Second, we investigate the continuous counterpart of distance-to-points trajectory search where the query is long-standing and the set of returned trajectories needs to be maintained whenever updates occur to the query and/or the data. Third, we propose and study two practical variants of distance-to-points trajectory search, which take into account the temporal characteristics of the searched trajectories. Through an extensive experimental analysis with real trajectory data, we show that our range-based approach outperforms previous methods by at least one order of magnitude for the snapshot and up to several times for the continuous version of the queries. Numéro de notice : A2017-600 Thématique : GEOMATIQUE Nature : Article DOI : 10.1007/s10707-016-0267-9 En ligne : https://doi.org/10.1007/s10707-016-0267-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=86908 [article]

BIM : New perspectives / Nigel Alexander in GEO: Geoconnexion international, vol 16 n° 3 (March 2017)

Public [article]  inGEO: Geoconnexion international > vol 16 n° 3 (March 2017) . - pp 36 - 38 Titre : BIM : New perspectives Type de document : Article/Communication Auteurs : Nigel Alexander, Auteur Année de publication : 2017 Article en page(s) : pp 36 - 38 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes descripteurs IGN] analyse combinatoire (maths) [Termes descripteurs IGN] modélisation 3D du bâti BIM [Termes descripteurs IGN] réalité virtuelle Résumé : (auteur) The combination of Building Information Modelling and virtual reality has the potential to transform architecture, planning and construction around the world, says Nigel Alexander. Numéro de notice : A2017-054 Thématique : IMAGERIE Nature : Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84250 [article]

A Computationally efficient algorithm for fusing multispectral and hyperspectral images / Raúl Guerra in IEEE Transactions on geoscience and remote sensing, vol 54 n° 10 (October 2016)  

Public [article]  inIEEE Transactions on geoscience and remote sensing > vol 54 n° 10 (October 2016) . - pp 5712 - 5728 Titre : A Computationally efficient algorithm for fusing multispectral and hyperspectral images Type de document : Article/Communication Auteurs : Raúl Guerra, Auteur ; Sebastian Lopez, Auteur ; Roberto Sarmiento, Auteur Année de publication : 2016 Article en page(s) : pp 5712 - 5728 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image optique [Termes descripteurs IGN] algorithme de fusion [Termes descripteurs IGN] analyse combinatoire (maths) [Termes descripteurs IGN] fusion d'images [Termes descripteurs IGN] image hyperspectrale [Termes descripteurs IGN] image multibande [Termes descripteurs IGN] qualité d'image Résumé : (auteur) Remote sensing systems equipped with multispectral and hyperspectral sensors are able to capture images of the surface of the Earth at different wavelengths. In these systems, hyperspectral sensors typically provide images with a high spectral resolution but a reduced spatial resolution, while on the contrary, multispectral sensors are able to produce images with a rich spatial resolution but a poor spectral resolution. Due to this reason, different fusion algorithms have been proposed during the last years in order to obtain remotely sensed images with enriched spatial and spectral resolutions by wisely combining the data acquired for the same scene by multispectral and hyperspectral sensors. However, the algorithms so far proposed that are able to obtain fused images with a good spatial and spectral quality require a formidable amount of computationally complex operations that cannot be executed in parallel, which clearly prevent the utilization of these algorithms in applications under real-time constraints in which high-performance parallel-based computing systems are normally required for accelerating the overall process. On the other hand, there are other state-of-the-art algorithms that are capable of fusing these images with a lower computational effort but at the cost of decreasing the quality of the resultant fused image. In this paper, a new algorithm named computationally efficient algorithm for fusing multispectral and hyperspectral images (CoEf-MHI) is proposed in order to obtain a high-quality image from hyperspectral and multispectral images of the same scene with a low computational effort. The proposed CoEf-MHI algorithm is based on incorporating the spatial details of the multispectral image into the hyperspectral image, without introducing spectral distortions. To achieve this goal, the CoEf-MHI algorithm first spatially upsamples, by means of a bilinear interpolation, the input hyperspectral image to the spatial resolution of the input multispectral image, and then, it independently refines each pixel of the resulting image by linearly combining the multispectral and hyperspectral pixels in its neighborhood. The simulations performed in this work with different images demonstrate that our proposal is much more efficient than state-of-the-art approaches, being this efficiency understood as the ratio between the quality of the fused image and the computational effort required to obtain such image. Numéro de notice : A2016-860 Thématique : IMAGERIE Nature : Article nature-HAL : ArtAvecCL-RevueIntern En ligne : http://dx.doi.org/10.1109/TGRS.2016.2570433 Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=82889 [article]

SPAWNN: A toolkit for SPatial Analysis With Self-Organizing Neural Networks / Julian Hagenauer in Transactions in GIS, vol 20 n° 5 (October 2016)  

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Geographically weighted evidence combination approaches for combining discordant and inconsistent volunteered geographical information / Alexis Comber in Geoinformatica [en ligne], vol 20 n° 3 (July - September 2016)  

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Toward a generalizable image representation for large-scale change detection : application to generic damage analysis / Lionel Gueguen in IEEE Transactions on geoscience and remote sensing, vol 54 n° 6 (June 2016)  

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An enhanced algorithm to estimate BDS satellite’s differential code biases / Chuang Shi in Journal of geodesy, vol 90 n° 2 (February 2016)  

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Combining spaceborne SAR images with 3D point clouds for infrastructure monitoring applications / Andrei Anghel in ISPRS Journal of photogrammetry and remote sensing, vol 111 (January 2016)

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Simplifying photogrammetric analysis for assessment of large mammal mass : automated targeting and 3D model building / L. Catherine Bester in Photogrammetric record, vol 30 n° 150 (June - August 2015)  

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Méthode de factorisation progressive pour accroître l’abstraction d’un modèle de classes / André Miralles in Ingénierie des systèmes d'information, ISI : Revue des sciences et technologies de l'information, RSTI, vol 20 n° 2 (mars - avril 2015)  

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Calibration of area based diameter distribution with individual tree based diameter estimates using airborne laser scanning / Qing Xu in ISPRS Journal of photogrammetry and remote sensing, vol 93 (July 2014)

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Instantaneous BeiDou+GPS RTK positioning with high cut-off elevation angles / Peter J.G. Teunissen in Journal of geodesy, vol 88 n° 4 (April 2014)  

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Spatial and spectral image fusion using sparse matrix factorization / Bo Huang in IEEE Transactions on geoscience and remote sensing, vol 52 n° 3 (March 2014)  

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