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Spatial accuracy of UAV- derived orthoimagery and topography: Comparing photogrammetric models processed with direct geo-referencing and ground control points / Chris H. Hugenholtz in Geomatica, vol 70 n° 1 (March 2016)
[article]
Titre : Spatial accuracy of UAV- derived orthoimagery and topography: Comparing photogrammetric models processed with direct geo-referencing and ground control points Type de document : Article/Communication Auteurs : Chris H. Hugenholtz, Auteur ; Owen Brown, Auteur ; Jordan Walker, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 21 - 30 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques
[Termes IGN] acquisition de données
[Termes IGN] analyse comparative
[Termes IGN] capteur aérien
[Termes IGN] drone
[Termes IGN] géoréférencement direct
[Termes IGN] point d'appui
[Termes IGN] positionnement cinématique en temps réel
[Termes IGN] positionnement inertiel
[Termes IGN] positionnement par GNSS
[Termes IGN] positionnement par GPS
[Termes IGN] qualité des données
[Termes IGN] réalité de terrain
[Termes IGN] topographieRésumé : (auteur) Mapping with unmanned aerial vehicles (UAVs) typically involves the deployment of ground control points (GCPs) to georeference the images and topographic model. An alternative approach is direct georeferencing, whereby the onboard Global Navigation Satellite System (GNSS) and inertial measurement unit are used without GCPs to locate and orient the data. This study compares the spatial accuracy of these approaches using two nearly identical UAVs. The onboard GNSS is the one difference between them, as one vehicle uses a survey-grade GNSS/RTK receiver (RTK UAV), while the other uses a lower-grade GPS receiver (non-RTK UAV). Field testing was performed at a gravel pit, with all ground measurements and aerial surveying completed on the same day. Three sets of orthoimages and DSMs were produced for comparing spatial accuracies: two sets were created by direct georeferencing images from the RTK UAV and non-RTK UAV and one set was created by using GCPs during the external orientation of the non-RTK UAV images. Spatial accuracy was determined from the horizontal (X,Y) and vertical (Z) residuals and root-mean-square-errors (RMSE) relative to 17 horizontal and 180 vertical check points measured with a GNSS/RTK base station and rover. For the two direct georeferencing datasets, the horizontal and vertical accuracy improved substantially with the survey-grade GNSS/RTK receiver onboard the RTK UAV, effectively reducing the RMSE values in X, Y and Z by 1 to 2 orders of magnitude compared to the lower grade GPS receiver onboard the non-RTK UAV. Importantly, the horizontal accuracy of the RTK UAV data processed via direct georeferencing was equivalent to the horizontal accuracy of the non-RTK UAV data processed with GCPs, but the vertical error of the DSM from the RTK UAV data was 2 to 3 times greater than the DSM from the non-RTK data with GCPs. Overall, results suggest that direct georeferencing with the RTK UAV can achieve horizontal accuracy comparable to that obtained with a network of GCPs, but for topographic measurements requiring the highest achievable accuracy, researchers and practitioners should use GCPs. Numéro de notice : A2016-433 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article DOI : 10.5623/cig2016-102 En ligne : https://doi.org/10.5623/cig2016-102 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=81330
in Geomatica > vol 70 n° 1 (March 2016) . - pp 21 - 30[article]The use of laser scanning as a method for measuring stairways following an accident / M. Eyre in Survey review, vol 48 n° 347 (March 2016)
[article]
Titre : The use of laser scanning as a method for measuring stairways following an accident Type de document : Article/Communication Auteurs : M. Eyre, Auteur ; P. J. Foster, Auteur ; K. Hallas, Auteur ; R. Shaw, Auteur Année de publication : 2016 Article en page(s) : pp 121 - 129 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Topographie moderne
[Termes IGN] analyse spatiale
[Termes IGN] architecture
[Termes IGN] carte d'intérieur
[Termes IGN] dommage physique
[Termes IGN] inclinomètre (topographie)
[Termes IGN] lever des détails
[Termes IGN] reconstruction 3D
[Termes IGN] surveillance d'ouvrage
[Termes IGN] télémétrie laser terrestreRésumé : (auteur) Stairs present significant potential for harm to their users. A fall on stairs, particularly in descent, often leads to serious injury or even death. The authors have been involved in the investigation of many workplace stair accidents. Proper forensic investigation into the cause of a stair accident has often found the incident to be wholly or partly caused by poor stair design. In order to establish the relationship between the stair design and a given fall, an onsite survey has to be conducted, determining the rises and goings along with other key dimensions. The Health and Safety Laboratory (HSL), Buxton, UK, regularly undertake this type of survey using a digital inclinometer, a steel rule and a tape measure. Laser scanning is an emerging technique that is now accessible to the surveyor to complement or replace traditional approaches. The laser scanner and associated software produces a dense point survey in 3D, allowing dimensional analysis of the features. The authors used both traditional and laser scanning techniques to study the scenes of two fatal stair falls. The analysis presented allows the suitability of laser scanning for stair-fall investigation to be considered. Identification and classification of errors are needed in order to consider if the error is acceptable or can be mitigated. Laser scanners are impressive instruments providing data from which can be used to create a virtual 3D environment that can be used to reconstruct and explain an event and contributing factors. The use of both survey methods currently provides the investigator with complimentary data that allows accurate measurements to be presented in the context of the three-dimensional environment. Numéro de notice : A2016-048 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.1179/1752270615Y.0000000014 En ligne : https://doi.org/10.1179/1752270615Y.0000000014 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79642
in Survey review > vol 48 n° 347 (March 2016) . - pp 121 - 129[article]Contribution of mass density heterogeneities to the quasigeoid-to-geoid separation / Robert Tenzer in Journal of geodesy, vol 90 n° 1 (January 2016)
[article]
Titre : Contribution of mass density heterogeneities to the quasigeoid-to-geoid separation Type de document : Article/Communication Auteurs : Robert Tenzer, Auteur ; Christian Hirt, Auteur ; Pavel Novák, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 65-80 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] anomalie de pesanteur
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] harmonique sphérique
[Termes IGN] masse de la Terre
[Termes IGN] modèle de densité
[Termes IGN] quasi-géoïde
[Termes IGN] topographieRésumé : (auteur) The geoid-to-quasigeoid separation is often computed only approximately as a function of the simple planar Bouguer gravity anomaly and the height of the computation point while disregarding the contributions of terrain geometry and anomalous topographic density as well as the sub-geoid masses. In this study we demonstrate that these contributions are significant and, therefore, should be taken into consideration when investigating the relation between the normal and orthometric heights particularly in the mountainous, polar and geologically complex regions. These contributions are evaluated by applying the spectral expressions for gravimetric forward modelling and using the EIGEN-6C4 gravity model, the Earth2014 datasets of terrain, ice thickness and inland bathymetry and the CRUST1.0 sediment and (consolidated) crustal density data. Since the global crustal density models currently available (e.g. CRUST1.0) have a limited accuracy and resolution, the comparison of individual density contributions is—for consistency—realized with a limited spectral resolution up to a spherical harmonic degree 360 (or 180). The results reveal that the topographic contribution globally varies between −0.33 and 0.57 m, with maxima in Himalaya and Tibet. The contribution of ice considerably modifies the geoid-to-quasigeoid separation over large parts of Antarctica and Greenland, where it reaches ∼0.2 m. The contributions of sediments and bedrock are less pronounced, with the values typically varying only within a few centimetres. These results, however, have still possibly large uncertainties due to the lack of information on the actual sediment and bedrock density. The contribution of lakes is mostly negligible; its maxima over the Laurentian Great Lakes and the Baikal Lake reach only several millimetres. The contribution of the sub-geoid masses is significant. It is everywhere negative and reaches extreme values of −4.43 m. According to our estimates, the geoid-to-quasigeoid separation globally varies within −4.19 and 0.26 m while the corresponding values computed according to a classical definition are only negative and reach extreme values of −3.5 m. A comparison of these results reveals that inaccuracies caused by disregarding the terrain geometry and mass density heterogeneities distributed within the topography and below the geoid surface can reach ±2 m or more in the mountainous regions. Numéro de notice : A2016-019 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0858-5 Date de publication en ligne : 01/10/2015 En ligne : https://doi.org/10.1007/s00190-015-0858-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79466
in Journal of geodesy > vol 90 n° 1 (January 2016) . - pp 65-80[article]
Titre : Filtrage de Kalman à bruits corrélés pour le positionnement précis Type de document : Mémoire Auteurs : Ulrich Mambou Kuipou, Auteur Editeur : Le Mans : Ecole Supérieure des Géomètres et Topographes ESGT Année de publication : 2016 Importance : 75 p. Format : 21 x 30 cm Note générale : bibliographie
Mémoire présenté en vue d'obtenir le diplôme d'Ingénieur CNAM, Spécialité Géomètre et TopographeLangues : Français (fre) Descripteur : [Vedettes matières IGN] Traitement du signal
[Termes IGN] analyse de variance
[Termes IGN] auscultation topographique
[Termes IGN] bruit blanc
[Termes IGN] corrélation temporelle
[Termes IGN] estimateur
[Termes IGN] étalonnage des données
[Termes IGN] filtre de Kalman
[Termes IGN] méthode de Monte-Carlo par chaînes de Markov
[Termes IGN] méthode des moindres carrés
[Termes IGN] méthode du maximum de vraisemblance (estimation)
[Termes IGN] précision du positionnement
[Termes IGN] topométrie de précisionRésumé : (auteur) Le filtre de Kalman à bruits corrélés peut être considéré comme une alternative aux solutions de filtrage classique, car il améliore la précision du positionnement. Les applications de ce nouveau filtre seraient très intéressantes pour le couplage de mesures dans les domaines suivants : photogrammétrie, télédétection aérienne, bathymétrie et «mobile mapping». L’objectif visé par ce travail de fin d’études, est d’évaluer les performances du filtre de Kalman à bruits corrélés dans une expérience d’auscultation. Dans l’optique de mettre en évidence la puissance de ce filtre, il y a lieu d’estimer par le maximum de vraisemblance, d’une part la variance du modèle d’évolution et d’autre part la corrélation des modèles (même corrélation de bruits, pour les modèles d’évolution et d’observation) en fixant au préalable une structure de corrélation aux dits modèles. Note de contenu : Introduction
1- Expérience de Bogatin
2- Méthode de calibration et résultat du filtrage de Kalman
3- Bruits corrélés : estimation et filtrage de Kalman à bruits corrélés
4- Applications sur des données réellesNuméro de notice : 24612 Affiliation des auteurs : non IGN Thématique : MATHEMATIQUE/POSITIONNEMENT Nature : Mémoire ingénieur ESGT Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92178 Documents numériques
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Filtrage de Kalman à bruits ... - pdf auteurAdobe Acrobat PDF A function-based linear map symbol building and rendering method using shader language / Songshan Yue in International journal of geographical information science IJGIS, vol 30 n° 1-2 (January - February 2016)
[article]
Titre : A function-based linear map symbol building and rendering method using shader language Type de document : Article/Communication Auteurs : Songshan Yue, Auteur ; Jianshun Yang, Auteur ; Min Chen, Auteur ; et al., Auteur Année de publication : 2016 Article en page(s) : pp 143 - 167 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] communication cartographique
[Termes IGN] détail topographique
[Termes IGN] figuré linéaire
[Termes IGN] rendu réaliste
[Termes IGN] route
[Termes IGN] signe conventionnel
[Termes IGN] Styled Layer Descriptor
[Termes IGN] symbole graphique
[Termes IGN] visée oblique
[Vedettes matières IGN] CartologieRésumé : (auteur) Maps are widely used to visualize geo-information so that map users can develop related understandings about the real world. Such a process for communicating information is largely dependent on the rendering of map elements using different symbols (points and linear and area symbols). To meet the demand of more dynamic and comprehensive visualization in map rendering, it is essential to improve the rendering efficiency. This paper focuses on these research topics, especially the difficulty in constructing and drawing linear map symbols. By employing shader language, a function-based linear symbol building and rendering method is presented in this paper. The basic idea of this function-based method is to build a map-rendering solution that employs graphic processing unit (GPU) acceleration technology to improve the rendering efficiency. A ‘function’ is used to represent the algorithm that draws certain simple or complex linear map symbols. This function reflects the structure of a linear map symbol (describing the symbol construction information) and also the rendering process of the symbolized linear map elements (handled on a per-pixel basis by the shader program). Based on the Open Geospatial Consortium (OGC), Styled Layer Descriptor (SLD) specifications, four basic line types (i.e., solid lines, dashed lines, gradient color lines, and transition lines) are implemented in the proposed method, and the implementation of line markers, line joins and line caps is also discussed. Three experiments are conducted to demonstrate improvements in map rendering. The results show that a variety of linear map symbols can be constructed in a uniform way, which suggests that the proposed method addresses the difficulty in drawing linear map symbols. With this method, the efficiency of rendering linear map elements is substantially improved compared to using the graphics device interface plus (GDI+) and anti-grain geometry (AGG) methods; it also provides an applicable approach for developing map rendering systems. Using this function-based concept, the complexity of building linear map symbols and drawing linear map elements can be decreased. Numéro de notice : A2016-086 Affiliation des auteurs : non IGN Thématique : GEOMATIQUE Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/13658816.2015.1077964 En ligne : https://doi.org/10.1080/13658816.2015.1077964 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79871
in International journal of geographical information science IJGIS > vol 30 n° 1-2 (January - February 2016) . - pp 143 - 167[article]Réservation
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