Oblique Multi-Camera Systems – Orientation and Dense Matching Issues

Abstract

ABS TRACT:The use of oblique imagery has become a standard for many civil and mapping applications, thanks to the development of airborne digital multi-camera systems, as proposed by many companies (Blomoblique, IGI, Leica, M idas, Pictometry, Vexcel/M icrosoft, VisionM ap, etc.). The indisputable virtue of oblique photography lies in its simplicity of interpretation and understanding for inexperienced users allowing their use of oblique images in very different applications, such as building detection and reconstruction, building structural damage classification, road land updating and administration services, etc. The paper reports an overview of the actual oblique commercial systems and presents a workflow for the automated orientation and dense matching of large image blocks. Perspectives, potentialities, pitfalls and suggestions for achieving satisfactory results are given. Tests performed on two datasets acquired with two multi-camera systems over urban areas are also reported.Figure 1: Large urban area pictured with an oblique multi-camera system. Once advanced image triangulation methods have retrieved interior and exterior parameters of the cameras, dense point clouds can be deriv ed for 3D city modelling, feature extraction and mapping purposes.

CHANGING THE PRODUCTION PIPELINE – USE OF OBLIQUE AERIAL CAMERAS FOR MAPPING PURPOSES

“…From an algorithmic point of view, this means coping with the well-known potential difficulties of DIM in oblique scenarios, i.e. large scale variations, multiple occlusions and severe illumination changes (Rupnik et al, 2014). Furthermore, the traditional 2.5D processing for DSM raster production from nadir images should be replaced by a more compelling modelling in "real" 3D space.…”

THE INFLUENCE OF FLIGHT PLANNING AND CAMERA ORIENTATION IN UAVs PHOTOGRAMMETRY. A TEST IN THE AREA OF ROCCA SAN SILVESTRO (LI), TUSCANY

“…The use of these acquisitions, where the lens axis of the camera is configured with a variable inclination, has a considerable impact in the generation of a 3D model from a photogrammetric survey, especially in case of complex objects or sites that present standing structures with a considerable height. As mentioned before, several researchers focussed their attention on the study of these specific images and in the optimization of the algorithms for the use of these "non-conventional" views (Gerke, 2009;Höhle, 2008;Remondino et al, 2016;Rupnik et al, 2014). Two previous experiences that were developed by the Geomatic group of the Politecnico di Torino were connected to the topic of oblique cameras utilization: one was conducted on the S. Maria Chapel, part of the Novalesa Abbey, and the other one on the Hercules Fountain in the gardens of Venaria Reale Chiabrando et al, 2016).…”

Reconstructing Buildings With Discontinuities and Roof Overhangs From Oblique Aerial Imagery

“…This will merely accommodate matching inaccuracies that for instance are caused by periodic patterns in the scene or sensor noise. However, the bilateral filter will not affect any positional noise that is introduced when the DSMs are triangulated and to which in particular the oblique views are prone because of their special characteristics (Rupnik et al, 2014). Therefore, after obtaining the 3D point clouds from the DSMs, another voxel-based filter must be executed to further reduce the noise level to be able to also model small building discontinuities later on.…”