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Minimising systematic error surfaces in digital elevation models using oblique convergent imagery / R. Wackrow in Photogrammetric record, vol 26 n° 133 (March - May 2011)  

Public [article]  inPhotogrammetric record > vol 26 n° 133 (March - May 2011) . - pp 16 - 31 Titre : Minimising systematic error surfaces in digital elevation models using oblique convergent imagery Type de document : Article/Communication Auteurs : R. Wackrow, Auteur ; Jim H. Chandler, Auteur Année de publication : 2011 Article en page(s) : pp 16 - 31 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes descripteurs IGN] angle de visée [Termes descripteurs IGN] déformation de surface [Termes descripteurs IGN] erreur systématique [Termes descripteurs IGN] image oblique [Termes descripteurs IGN] inondation [Termes descripteurs IGN] modèle numérique de surface [Termes descripteurs IGN] photogrammétrie terrestre Résumé : (Auteur) There are increasing opportunities to use consumer-grade digital cameras, particularly if accurate spatial data can be captured. Research recently conducted at Loughborough University identified residual systematic error surfaces or domes discernible in digital elevation models (DEMs). These systematic effects are often associated with such cameras and are caused by slightly inaccurate estimated lens distortion parameters. A methodology that minimises the systematic error surfaces was therefore developed, using a mildly convergent image configuration in a vertical perspective. This methodology was tested through simulation and a series of practical tests. This paper investigates the potential of the convergent configuration to minimise the error surfaces, even if the geometrically more complex oblique perspective is used. Initially, simulated data was used to demonstrate that an oblique convergent image configuration can minimise remaining systematic error surfaces using various imaging angles. Additionally, practical tests using a laboratory testfield were conducted to verify results of the simulation. The need to develop a system to measure the topographic surface of a flooding river provided the opportunity to verify the findings of the simulation and laboratory test using real data. Results of the simulation process, the laboratory test and the practical test are reported in this paper and demonstrate that an oblique convergent image configuration eradicates the systematic error surfaces which result from inaccurate lens distortion parameters. This approach is significant because by removing the need for an accurate lens model it effectively improves the accuracies of digital surface representations derived using consumer-grade digital cameras. Carefully selected image configurations could therefore provide new opportunities for improving the quality of photogrammetrically acquired data. Numéro de notice : A2011-076 Thématique : IMAGERIE Nature : Article DOI : 10.1111/j.1477-9730.2011.00623.x date de publication en ligne : 16/03/2011 En ligne : https://doi.org/10.1111/j.1477-9730.2011.00623.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30857 [article]

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Incremental segmentation of lidar point clouds with an octree-structured voxel space / M. Wang in Photogrammetric record, vol 26 n° 133 (March - May 2011)  

Public [article]  inPhotogrammetric record > vol 26 n° 133 (March - May 2011) . - pp 32 - 57 Titre : Incremental segmentation of lidar point clouds with an octree-structured voxel space Type de document : Article/Communication Auteurs : M. Wang, Auteur ; Y.H. Tseng, Auteur Année de publication : 2011 Article en page(s) : pp 32 - 57 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie [Termes descripteurs IGN] coplanarité [Termes descripteurs IGN] données lidar [Termes descripteurs IGN] données localisées 3D [Termes descripteurs IGN] octree [Termes descripteurs IGN] reconstruction d'objet [Termes descripteurs IGN] segmentation [Termes descripteurs IGN] semis de points [Termes descripteurs IGN] voxel Résumé : (Auteur) Lidar (light detection and ranging) data implicitly contains abundant three-dimensional spatial information. The segmentation of lidar point clouds is the key procedure for transforming implicit spatial information into explicit spatial information. Common criteria used for point cloud segmentation are proximity and coherence of point distribution. An effective segmentation algorithm may apply various steps or combinations of criteria depending on the application. This paper proposes a four-step segmentation method for lidar point clouds to deliver incremental segmentation results. Segmentation results of each step can provide the fundamental data for the next step. In the first step, the input point cloud is organised into an octree-structured voxel space, in which the point neighbourhood is established. In the second step, connected voxels which are not empty are grouped to obtain grouped points based on proximity. The third step is a coplanar point segmentation based on both coherence and proximity, which was performed on each point group obtained in the second step. Finally, neighbouring coplanar point groups are merged into “co-surface” point groups based on the criteria of plane connection and intersection. This scheme enables an incremental retrieval and analysis of a large lidar data-set. Experimental results demonstrate the effectiveness of the segmentation algorithm in handling both airborne and terrestrial lidar data. It is anticipated that the incremental segmentation results will be useful for object modelling using lidar data. Numéro de notice : A2011-077 Thématique : IMAGERIE Nature : Article DOI : 10.1111/j.1477-9730.2011.00624.x date de publication en ligne : 16/03/2011 En ligne : https://doi.org/10.1111/j.1477-9730.2011.00624.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30858 [article]

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Indirect georeferencing of digital SLR [single-lens reflex] imagery using signalised lidar control points / E. Mitishita in Photogrammetric record, vol 26 n° 133 (March - May 2011)  

Public [article]  inPhotogrammetric record > vol 26 n° 133 (March - May 2011) . - pp 58 - 72 Titre : Indirect georeferencing of digital SLR [single-lens reflex] imagery using signalised lidar control points Type de document : Article/Communication Auteurs : E. Mitishita, Auteur ; J. Cortes, Auteur ; J. Centeno, Auteur Année de publication : 2011 Article en page(s) : pp 58 - 72 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Photogrammétrie numérique [Termes descripteurs IGN] analyse comparative [Termes descripteurs IGN] compensation par faisceaux [Termes descripteurs IGN] données lidar [Termes descripteurs IGN] géoréférencement indirect [Termes descripteurs IGN] image numérique [Termes descripteurs IGN] point d'appui [Termes descripteurs IGN] positionnement par GPS Résumé : (Auteur) Photogrammetric and lidar data-sets have been used together in mapping procedures because of their complementary characteristics. However, to perform this integration both data-sets must be within a common reference frame. Although all lidar systems include a direct georeferencing procedure, the majority of low-cost photogrammetric systems do not have a facility for direct georeferencing of images even if the data-sets are captured simultaneously. In recent years, the high accuracy of the lidar data has enabled it to provide a source of photogrammetric control and thus to offer indirect georeferencing. This paper presents a methodology for the indirect georeferencing of digital SLR images using signalised lidar control points, together with the results obtained. The intensity image and raw lidar data-set were used to extract 3D coordinates of signalised control points. Two bundle adjustments of 21 images were performed. In the first case the coordinates of the control points were obtained by using GPS survey. In the second, they were extracted from a lidar data-set. The results obtained from these experiments confirm the feasibility of the proposed methodology Numéro de notice : A2011-078 Thématique : IMAGERIE Nature : Article DOI : 10.1111/j.1477-9730.2011.00621.x date de publication en ligne : 16/03/2011 En ligne : https://doi.org/10.1111/j.1477-9730.2011.00621.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30859 [article]

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Acquisition of the 3D boundary of the Triglav glacier from archived non-metric panoramic images / M. Triglav-Cekada in Photogrammetric record, vol 26 n° 133 (March - May 2011)  

Public [article]  inPhotogrammetric record > vol 26 n° 133 (March - May 2011) . - pp 111 - 129 Titre : Acquisition of the 3D boundary of the Triglav glacier from archived non-metric panoramic images Type de document : Article/Communication Auteurs : M. Triglav-Cekada, Auteur ; R. Radovanovic, Auteur ; D. Radovan, Auteur ; M. Gabrovec, Auteur ; Mojca Kosmatin-Fras, Auteur Année de publication : 2011 Article en page(s) : pp 111 - 129 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications photogrammétriques [Termes descripteurs IGN] alpes orientales [Termes descripteurs IGN] analyse diachronique [Termes descripteurs IGN] angle vertical [Termes descripteurs IGN] chambre non métrique [Termes descripteurs IGN] chambre panoramique [Termes descripteurs IGN] données localisées 3D [Termes descripteurs IGN] glacier [Termes descripteurs IGN] modèle numérique de surface [Termes descripteurs IGN] montagne [Termes descripteurs IGN] numérisation de photographie [Termes descripteurs IGN] photographie argentique [Termes descripteurs IGN] Slovénie [Termes descripteurs IGN] volume (grandeur) Résumé : (Auteur) A panoramic, non-metric, Horizont camera has been used for regular, monthly, close-range photography of the rapidly retreating Triglav glacier in Slovenia since 1976. The unfavourable geometry of the convergent images taken from the two camera stations has made any direct stereoscopic observation and recording impossible. The aim of this research was to define the most useful method for acquiring 3D data from these panoramic, convergent images. The Horizont camera was calibrated and three methods were then tested: the generation of pseudo-orthophotographs, the application of 2D clinometry and the interactive orientation of a detailed digital elevation model (DEM) on the images. The third turned out to be the only method suitable for determining the boundary of the Triglav glacier. The interactive orientation of a detailed DEM on the Horizont images is described in detail. The 3D glacier boundary can be acquired from individual Horizont images (camera stations A and B) enabling the computation of the glacier’s area and theoretical volume. By repeating the glacier boundary acquisition for different orientation parameters, the standard deviations of the glacier area and theoretical volume were computed. Because of the more precise average area and volume measurements achieved with the camera station B images, only these were chosen for the glacier disappearance study. Every third year between 1976 and 2005 the Horizont images were used to compute the changes in the area and volume of the glacier. The glacier area was found to have reduced to 8% of its earlier size, from 15 ha in 1976 to 1·2 ha in 2000. However, owing to harsher than average winters since then the decline in the glacier area was found to have slowed in the past decade (2000 to 2009). The glacier’s theoretical volume decreased roughly exponentially from 1976 to 2005 Numéro de notice : A2011-079 Thématique : IMAGERIE Nature : Article DOI : 10.1111/j.1477-9730.2011.00622.x date de publication en ligne : 16/03/2011 En ligne : https://doi.org/10.1111/j.1477-9730.2011.00622.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30860 [article]

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