Assessment of a photogrammetric approach for urban DSM extraction from tri-stereoscopic satellite imagery

Built-up environments are extremely complex for 3D surface modelling purposes. The main distortions that hamper 3D reconstruction from 2D imagery are image dissimilarities, concealed areas, shadows, height discontinuities and discrepancies between smooth terrain and man-made features. A methodology is proposed to improve automatic photogrammetric extraction of an urban surface model from high resolution satellite imagery with the emphasis on strategies to reduce the effects of the cited distortions and to make image matching more robust. Instead of a standard stereoscopic approach, a digital surface model is derived from tri-stereoscopic satellite imagery. This is based on an extensive multi-image matching strategy that fully benefits from the geometric and radiometric information contained in the three images. The bundled triplet consists of an IKONOS along-track pair and an additional near-nadir IKONOS image. For the tri-stereoscopic study a densely built-up area, extending from the centre of Istanbul to the urban fringe, is selected. The accuracy of the model extracted from the IKONOS triplet, as well as the model extracted from only the along-track stereopair, are assessed by comparison with 3D check points and 3D building vector data

A 3D Omnidirectional Sensor For Mobile Robot Applications

International audienc

Airborne photogrammetry and LIDAR for DSM extraction and 3D change detection over an urban area : a comparative study

A digital surface model (DSM) extracted from stereoscopic aerial images, acquired in March 2000, is compared with a DSM derived from airborne light detection and ranging (lidar) data collected in July 2009. Three densely built-up study areas in the city centre of Ghent, Belgium, are selected, each covering approximately 0.4 km(2). The surface models, generated from the two different 3D acquisition methods, are compared qualitatively and quantitatively as to what extent they are suitable in modelling an urban environment, in particular for the 3D reconstruction of buildings. Then the data sets, which are acquired at two different epochs t(1) and t(2), are investigated as to what extent 3D (building) changes can be detected and modelled over the time interval. A difference model, generated by pixel-wise subtracting of both DSMs, indicates changes in elevation. Filters are proposed to differentiate 'real' building changes from false alarms provoked by model noise, outliers, vegetation, etc. A final 3D building change model maps all destructed and newly constructed buildings within the time interval t(2) - t(1). Based on the change model, the surface and volume of the building changes can be quantified

New metric products, movies and 3D models from old stereopairs and their application to the in situ palaeontological site of Ambrona

[ES] Este artículo está basado en la información del siguiente proyecto:● LDGP_mem_006-1: "[S_Ambrona_Insitu] Levantamiento fotogramétrico del yacimiento paleontológico “Museo in situ” de Ambrona (Soria)", http://hdl.handle.net/10810/7353● LDGP_mem_006-1: "[S_Ambrona_Insitu] Levantamiento fotogramétrico del yacimiento paleontológico “Museo in situ” de Ambrona (Soria)", http://hdl.handle.net/10810/7353[EN] This paper is based on the information gathered in the following project:[EN] 3D modelling tools from photographic pictures have experienced significant improvements in the last years. One of the most outstanding changes is the spread of the photogrammetric systems based on algorithms referred to as Structure from Motion (SfM) in contrast with the traditional stereoscopic pairs. Nevertheless, the availability of important collections of stereoscopic registers collected during past decades invites us to explore the possibilities for re-using these photographs in order to generate new multimedia products, especially due to the fact that many of the documented elements have been largely altered or even disappeared. This article analyses an example of application to the re-use of a collection of photographs from the palaeontological site of Ambrona (Soria, Spain). More specifically, different pieces of software based on Structure from Motion (SfM) algorithms for the generation of 3D models with photographic textures are tested and some derived products such as orthoimages, video or applications of Augmented Reality (AR) are presented.[ES] Las herramientas de modelado 3D a partir de imágenes fotográficas han experimentado avances muy significativos en los últimos años. Uno de los más destacados corresponde a la generalización de los sistemas fotogramétricos basados en los algoritmos denominados Structure from Motion (SfM) sobre los proyectos de documentación tradicional basados en pares estereoscópicos. La existencia de importantes colecciones de registros estereoscópicos realizados durante las décadas anteriores invita a explorar las posibilidades de reutilización de estos registros para la obtención de productos multimedia actuales, máxime cuando algunos de los elementos documentados han sufrido grandes modificaciones o incluso desaparecido. En el presente artículo se analiza la reutilización de colecciones fotográficas de yacimientos paleontológicos mediante un ejemplo centrado en el yacimiento de Ambrona (Soria, España). En concreto, se contrastan varios programas basados en los algoritmos denominados Structure from Motion (SfM) para la generación del modelo 3D con textura y otros productos derivados como ortoimágenes, vídeos o aplicaciones de Realidad Aumentada (RA)

VBS RTK GPS-ASSISTED SELF-CALIBRATION BUNDLE ADJUSTMENT FOR AERIAL TRIANGULATION OF FIXED-WING UAS IMAGES FOR UPDATING TOPOGRAPHIC MAPS

Unmanned Aircraft Systems (UASs) can collect high resolution and high quality images for local mapping. If the highly accurate GPS flying trajectory of a UAS is collected, it can support bundle adjustment aerial triangulation (AT) of UAS images and reduce the demands on ground control points (GCPs). This study installs a Trimble BD970 GNSS OEM on a fixed-wing UAS for capturing highly accurate GPS data by using a Virtual Base Station (VBS) RTK GPS technique for AT. Meanwhile, the GPS antenna-camera offset is resolved by stripwise linear drift parameters introduced in GPS observation equations, while performing bundle adjustment for AT. Additionally, self-calibration bundle adjustment is used in VBS RTK GPS-assisted AT to solve incomplete camera parameters calibrated by a close-range photogrammetric approach. The results show that the AT accuracy of fixed-wing UAS images collected with a 24 mm focal-length Canon EOS 5D Mark II camera at a flying height of 550 m above ground level is 0.21 m in planimetry and 0.22 m in height using two cross strips with two full GCPs at each corner of the block. The RMSE of check points from stereoscopic viewing can reach 0.27 m in planimetry and 0.24 m in height. The test results show that the accuracy of VBS RTK GPS-assisted bundle adjustment with self-calibration for the AT of fixed-wing UAS image can be used for updating local 1/5000 topographic maps in Taiwan

Camera positioning for 3D panoramic image rendering

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University London.Virtual camera realisation and the proposition of trapezoidal camera architecture are the two broad contributions of this thesis. Firstly, multiple camera and their arrangement constitute a critical component which affect the integrity of visual content acquisition for multi-view video. Currently, linear, convergence, and divergence arrays are the prominent camera topologies adopted. However, the large number of cameras required and their synchronisation are two of prominent challenges usually encountered. The use of virtual cameras can significantly reduce the number of physical cameras used with respect to any of the known camera structures, hence adequately reducing some of the other implementation issues. This thesis explores to use image-based rendering with and without geometry in the implementations leading to the realisation of virtual cameras. The virtual camera implementation was carried out from the perspective of depth map (geometry) and use of multiple image samples (no geometry). Prior to the virtual camera realisation, the generation of depth map was investigated using region match measures widely known for solving image point correspondence problem. The constructed depth maps have been compare with the ones generated using the dynamic programming approach. In both the geometry and no geometry approaches, the virtual cameras lead to the rendering of views from a textured depth map, construction of 3D panoramic image of a scene by stitching multiple image samples and performing superposition on them, and computation of virtual scene from a stereo pair of panoramic images. The quality of these rendered images were assessed through the use of either objective or subjective analysis in Imatest software. Further more, metric reconstruction of a scene was performed by re-projection of the pixel points from multiple image samples with a single centre of projection. This was done using sparse bundle adjustment algorithm. The statistical summary obtained after the application of this algorithm provides a gauge for the efficiency of the optimisation step. The optimised data was then visualised in Meshlab software environment, hence providing the reconstructed scene. Secondly, with any of the well-established camera arrangements, all cameras are usually constrained to the same horizontal plane. Therefore, occlusion becomes an extremely challenging problem, and a robust camera set-up is required in order to resolve strongly the hidden part of any scene objects. To adequately meet the visibility condition for scene objects and given that occlusion of the same scene objects can occur, a multi-plane camera structure is highly desirable. Therefore, this thesis also explore trapezoidal camera structure for image acquisition. The approach here is to assess the feasibility and potential of several physical cameras of the same model being sparsely arranged on the edge of an efficient trapezoid graph. This is implemented both Matlab and Maya. The quality of the depth maps rendered in Matlab are better in Quality

A WORLDWIDE 3D GCP DATABASE INHERITED FROM 20 YEARS OF MASSIVE MULTI-SATELLITE OBSERVATIONS

Abstract. High location accuracy is a major requirement for satellite image users. Target performance is usually achieved thanks to either specific on-board satellite equipment or an auxiliary registration reference dataset. Both methods may be expensive and with certain limitations in terms of performance. The Institut national de l'information géographique et forestière (IGN) and Airbus Defence and Space (ADS) have worked together for almost 20 years, to build reference data for improving image location using multi-satellite observations. The first geometric foundation created has mainly used SPOT 5 High Resolution Stereoscopic (HRS) imagery, ancillary Ground Control Points (GCP) and Very High Resolution (VHR) imagery, providing a homogenous location accuracy of 10m CE90 almost all over the world in 2010.Space Reference Points (SRP) is a new worldwide 3D GCP database, built from a plethoric SPOT 6/7 multi-view archive, largely automatically processed, with cloud-based technologies. SRP aims at providing a systematic and reliable solution for image location (Unmanned Aerial Vehicle, VHR satellite imagery, High Altitudes Pseudo-Satellite…) and similar topics thanks to a high-density point distribution with a 3m CE90 accuracy.This paper describes the principle of SRP generation and presents the first validation results. A SPOT 6/7 smart image selection is performed to keep only relevant images for SRP purpose. The location of these SPOT 6/7 images is refined thanks to a spatiotriangulation on the worldwide geometric foundation, itself improved where needed. Points making up the future SRP database are afterward extracted thanks to classical feature detection algorithms and with respect to the expected density. Different filtering methods are applied to keep the best candidates. The last step of the processing chain is the formatting of the data to the delivery format, including metadata. An example of validation of SRP concept and specification on two tests sites (Spain and China) is then given. As a conclusion, the on-going production is shortly presented

ProSLAM: Graph SLAM from a Programmer's Perspective

In this paper we present ProSLAM, a lightweight stereo visual SLAM system designed with simplicity in mind. Our work stems from the experience gathered by the authors while teaching SLAM to students and aims at providing a highly modular system that can be easily implemented and understood. Rather than focusing on the well known mathematical aspects of Stereo Visual SLAM, in this work we highlight the data structures and the algorithmic aspects that one needs to tackle during the design of such a system. We implemented ProSLAM using the C++ programming language in combination with a minimal set of well known used external libraries. In addition to an open source implementation, we provide several code snippets that address the core aspects of our approach directly in this paper. The results of a thorough validation performed on standard benchmark datasets show that our approach achieves accuracy comparable to state of the art methods, while requiring substantially less computational resources.Comment: 8 pages, 8 figure