Integration of LiDAR and photogrammetric data for enhanced aerial triangulation and camera calibration

PhD ThesisThe integration of complementary airborne light detection and ranging (LiDAR) and photogrammetric data continues to receive attention from the relevant research communities. Such an approach requires the optimized registration of the two data types within a common coordinate reference frame and thus enables the cross-calibration of one information source against another. This research assumes airborne LiDAR as a reference dataset against which in-flight camera system calibration and validation can be performed. The novel methodology involves the production of dense photogrammetric point clouds derived using the simultaneous adjustment of GNSS/IMU data and a dense set of photogrammetric tie points. Quality of the generated photogrammetric dataset is further improved through introducing the self-calibration additional parameters in the combined adjustment. A robust least squares surface matching algorithm is then used to minimise the Euclidean distances between the two datasets. After successful matching, well distributed LiDAR-derived control points (LCPs) are automatically identified and extracted. Adjustment of the photogrammetric data is then repeated using extracted LCPs in a self-calibrating bundle adjustment. The research methodology was tested using two datasets acquired using different photogrammetric digital sensor systems, a Microsoft UltraCamX large format camera and an Applanix DSS322 medium format camera. Systematic sensitivity testing included the influence of the number and weighting of LCPs required to achieve optimised adjustment. For the UltraCamX block it was found that when the number of control points exceeded 80, the accuracy of the adjustment stabilized at c. 2 cm in all axes, regardless of point weighting. Results were also compared with those from reference calibration using surveyed ground control points in the test area, with good agreement found between the two. Similar results were obtained for the DSS322 block, with block accuracy stabilizing at 100 LCPs. Moreover, for the DSS322 camera, introducing self-calibration greatly improved the accuracy of aerial triangulation

Estudio y análisis geométrico de la cámara barredora ads40 en los procesos fotogramétricos

[ES] La reciente incorporación de los sensores de barrido de gran formato junto con su creciente uso en los proyectos fotogramétricos, debido al su elevado número de aplicaciones, ha fomentado el interés de la comunidad científica internacional por lograr un conocimiento profundo de este tipo de sensores. Las herramientas de los software fotogramétricos clásicos, utilizadas para las cámaras matriciales, deben adaptarse a la nueva y totalmente diferente filosofía de las cámaras de barrido, las cuales heredan el planteamiento de los sensores de barrido de teledetección con lo que este tipo de sensores supone una convergencia entre las disciplinas de teledetección y fotogrametría. Con el objetivo de contribuir al progreso de esta línea, esta Tesis recoge el funcionamiento de este tipo de sensores desde su calibración en laboratorio hasta la necesidad de autocalibración, así como los sistemas de coordenadas y modelos matemáticos inherentes a su funcionamiento, concretando en el funcionamiento de la segunda generación de Leica Geosystems, ADS40 SH52. Por otro lado se presentan los resultados obtenidos en el análisis geométrico de dicha cámara para diagnosticar su rendimiento en entornos reales, resultados provenientes de los procesos de aerotriangulación y autocalibración. Este análisis empírico se ha basado en el diseño de un campo de pruebas sobre la ciudad de Ávila, España, realizando dos vuelos a distinta altura y estableciendo una amplia red de puntos de apoyo y chequeo distribuidos homogéneamente sobre la superficie de vuelo. Estos puntos fueron medidos mediante técnicas topográficas para determinar la exactitud y fiabilidad de la cámara tras la aerotriangulación, resuelta a través de varios modelos matemáticos, y tras la autocalibración, utilizando los parámetros internos de la cámara: focal, punto principal, punto de mejor simetría y parámetros de distorsión radial. A través de estos test empíricos se aporta coherencia y estabilidad a la metodología establecida para actuar con este tipo de cámaras a fin de obtener mejoras en los tiempos y costes de producción, obteniendo la máxima precisión, tanto interna como externa, en el ajuste de haces.[EN]The recent development of the large format pushbroom sensors and its increasing role in the photogrammetric projects has opened a whole range of new applications and therefore, has fostered the international community concern to achieve a sound knowledge of these devices. The classic software tools, implemented for the frame cameras, need to be adapted to the new and different pushbroom approach, largely inherited from the remote sensing community. Consequently, a convergence between both disciplines is growing. With the aim of contributing to the progress of this trend, this document analyzes the working principles of these sensors, from the classical laboratory calibration approach up to the need of calibration in situ. To do so, the coordinate systems and the mathematical models are revised and specially, the second generation from Leica Geosystems, ADS40 SH52 is thoroughly explored. Besides this, the results from several procedures of aerial triangulation and self calibration to test the performance of these cameras in real environments are presented. This empirical analysis has relied on the design and development of a field test, close to the city of Avila, with a large and evenly distributed network of control and check points and on the execution of a two height flight with a cross strip configuration. The points were measured by means of geodetic techniques and have provided the necessary framework to assess the accuracy and reliability of several ways of computing the bundle adjustment. Aerial Triangulation was performed through a variety of functional models and the interior parameters – focal length, principal point, point of best symmetry and radial distortion parameters – were added to the best results achieved. By means of these empirical tests a coherent and stable insight of the pros and cons of the processing methodology concerning this type of sensors is acquired and thus, the understanding of the most profitable combination of performance and accuracy is improve

Modélisation et développement d'une plateforme intelligente pour la capture d'images panoramiques cylindriques

In most robotic applications, vision systems can significantly improve the perception of the environment. The panoramic view has particular attractions because it allows omnidirectional perception. However, it is rarely used because the methods that provide panoramic views also have significant drawbacks. Most of these omnidirectional vision systems involve the combination of a matrix camera and a mirror, rotating matrix cameras or a wide angle lens. The major drawbacks of this type of sensors are in the great distortions of the images and the heterogeneity of the resolution. Some other methods, while providing homogeneous resolutions, also provide a huge data flow that is difficult to process in real time and are either too slow or lacking in precision. To address these problems, we propose a smart panoramic vision system that presents technological improvements over rotating linear sensor methods. It allows homogeneous 360 degree cylindrical imaging with a resolution of 6600 × 2048 pixels and a precision turntable to synchronize position with acquisition. We also propose a solution to the bandwidth problem with the implementation of a feature etractor that selects only the invariant feaures of the image in such a way that the camera produces a panoramic view at high speed while delivering only relevant information. A general geometric model has been developped has been developped to describe the image formation process and a caligration method specially designed for this kind of sensor is presented. Finally, localisation and structure from motion experiments are described to show a practical use of the system in SLAM applications.Dans la plupart des applications de robotique, un système de vision apporte une amélioration significative de la perception de l’environnement. La vision panoramique est particulièrement intéressante car elle rend possible une perception omnidirectionnelle. Elle est cependant rarement utilisée en pratique à cause des limitations technologiques découlant des méthodes la permettant. La grande majorité de ces méthodes associent des caméras, des miroirs, des grands angles et des systèmes rotatifs ensembles pour créer des champs de vision élargis. Les principaux défauts de ces méthodes sont les importantes distorsions des images et l’hétérogénéité de la résolution. Certaines autres méthodes permettant des résolutions homogènes, prodiguent un flot de données très important qui est difficile à traiter en temps réel et sont soit trop lents soit manquent de précision. Pour résoudre ces problèmes, nous proposons la réalisation d’une caméra panoramique intelligente qui présente plusieurs améliorations technologiques par rapport aux autres caméras linéaires rotatives. Cette caméra capture des panoramas cylindriques homogènes avec une résolution de 6600 × 2048 pixels. La synchronisation de la capture avec la position angulaire est possible grâce à une plateforme rotative de précision. Nous proposons aussi une solution au problème que pose le gros flot de données avec l’implémentation d’un extracteur de primitives qui sélectionne uniquement les primitives invariantes des images pour donner un système panoramique de vision qui ne transmet que les données pertinentes. Le système a été modélisé et une méthode de calibrage spécifiquement conçue pour les systèmes cylindriques rotatifs est présentée. Enfin, une application de localisation et de reconstruction 3D est décrite pour montrer une utilisation pratique dans une application de type Simultaneous Localization And Mapping ( SLAM )

Laboratory for Atmospheres 2009 Technical Highlights

The 2009 Technical Highlights describes the efforts of all members of the Laboratory for Atmospheres. Their dedication to advancing Earth Science through conducting research, developing and running models, designing instruments, managing projects, running field campaigns, and numerous other activities, is highlighted in this report

6th International Meeting on Retouching of Cultural Heritage, RECH6

RECH Biennial Meeting is one of the largest educational and scientific events in Retouching field, an ideal venue for conservators and scientists to present their research results about retouching. The main focus will be to promote the exchange of ideas, concepts, terminology, methods, techniques and materials applied during the retouching process in different areas of conservation: mural painting, easel painting, sculpture, graphic documentation, architecture, plasterwork, photography, contemporary art, among others. This Meeting aims to address retouching by encouraging papers that contribute to a deeper understanding of this final task of the conservation and restoration intervention. The main theme embraces the concepts of retouching, the criteria and limits in the retouching process, the bad retouching impact on heritage and their technical and scientific developments.This Meeting will discuss real-life approaches on retouching, focusing on practical solutions and on sharing experiencesColomina Subiela, A.; Doménech García, B.; Bailão, A. (2023). 6th International Meeting on Retouching of Cultural Heritage, RECH6. Editorial Universitat Politècnica de València. https://doi.org/10.4995/RECH6.2021.1601

5th International Conference. Youth in Conservation of Cultural Heritage YOCOCU. Book of abstracts.

Depto. de Mineralogía y PetrologíaFac. de Ciencias GeológicasTRUEYouth in Conservation of Cultural Heritage - YOCOCU EspañaMuseo Centro de Arte Reina Sofía MNCARSFundación Reina Sofíapu