Automatic Processing of Many Images for 2D/3D Modelling

The era of big data requires increasing automation for the analysis of huge information in a short time and this need becomes critical when dealing with geoinformation. This chapter describes the automatic geocoding of digital images based on high-end Photogrammetric and Remote Sensing methods. In particular, the so-called Structure-from-Motion (SfM) technique is developed to handle image data sets in close-range applications, and here, it is generalized to deal with multi-scale applications. Some examples are proposed with panoramic images for the measurement of indoor narrow spaces, with smartphone cameras and UAV for the 3D reconstruction of complex monuments, as well as with airborne and satellite images for the survey at the territorial scale

Global Trifocal Adjustment

In this paper we introduce a fast and robust structure-less alternative to full bundle adjustment. The method is based on optimizing algebraic errors for trilinear constraints from triplets of views. It is shown that the error generated by a triplet of views can be described by a fixed triangular matrix regardless of the number of feature correspondences between the views. The method has been evaluated on various real and synthetic datasets and shows good convergence properties with a large convergence basin and solutions that are close to the optimal solution. The method has been compared to Global Epipolar Adjustment, GEA, which is based on the bilinear constraint. It will be shown that the method can handle the degenerate configurations of GEA

Structure-From-Motion Photogrammetry to Support the Assessment of Collapse Risk in Alpine Glaciers

The application of Structure-from-Motion (SfM) Photogrammetry with ground-based and UAV camera stations may be exploited for modelling the topographic surface of Alpine glaciers. Multi-temporal repeated surveys lead to geometric models that may be applied to analyze the glacier retreat under global warming conditions. Thanks to the integration of point clouds obtained from ground-based and UAV imaging platforms, a complete 3D reconstruction also including vertical and sub-vertical surfaces may be achieved. These 3D models may be also exploited to understand the precursory signals of local collapse that might represent a risk for tourists and hikers visiting glaciers. In this paper a review on the application of SfM Photogrammetry in the field of glaciological studies is reported. The case of Forni Glacier in the Italian Alps is presented as emblematic study. Photogrammetric data sets obtained from measurement campaigns carried out in 2014, 2016, 2017 and 2018 have been processed using a common workflow. Attention is paid to a few crucial aspects, such as image orientation and calibration, dense surface matching, georeferencing and data fusion. In the end, the use of output point clouds to evaluate the risk of collapse in the Forni Glacier is addressed

Multi-image 3D reconstruction: A photogrammetric and structure from motion comparative analysis

Virtual Web Reconstruction of cultural heritage is one of the most interesting and innovative tool to preserve historical, architectural and artistic memory of many sites, particularly the ones prone to disappear, as well as to promote territories and tourism development. Recently, high-resolution 3D models are realized through improved technology and integration of survey techniques such as laser scanning and photogrammetry. However, the large and complex volume of 3D data makes difficult to access and handle them for either experts and citizens. In particular, the rendering of large 3D models may influence the performance of web publication and browsing. Considering this background, the goal of this paper is the comparison between the level of accuracy and realism of 3D models optimized using two different mesh simplification. The metric used is based on the Hausdorff distance which is a generic technique to define a distance between two nonempty sets, considering 3D scanner mesh as a reference in the measure. The “Casale di Pacciano” near Bisceglie (Apulia region, Italy), has been investigated as study case