Uav Photogrammetry With Oblique Images: First Analysis on Data Acquisition and Processing

Abstract

Commission I, WG I/VbKEY WORDS: UAV, Oblique Imagery, photogrammetry, SfM, point clouds, cultural heritage, architectural 3D models ABSTRACT:In recent years, many studies revealed the advantages of using airborne oblique images for obtaining improved 3D city models (e.g. including façades and building footprints). Expensive airborne cameras, installed on traditional aerial platforms, usually acquired the data. The purpose of this paper is to evaluate the possibility of acquire and use oblique images for the 3D reconstruction of a historical building, obtained by UAV (Unmanned Aerial Vehicle) and traditional COTS (Commercial Off-the-Shelf) digital cameras (more compact and lighter than generally used devices), for the realization of high-level-of-detail architectural survey. The critical issues of the acquisitions from a common UAV (flight planning strategies, ground control points, check points distribution and measurement, etc.) are described. Another important considered aspect was the evaluation of the possibility to use such systems as low cost methods for obtaining complete information from an aerial point of view in case of emergency problems or, as in the present paper, in the cultural heritage application field. The data processing was realized using SfM-based approach for point cloud generation: different dense image-matching algorithms implemented in some commercial and open source software were tested. The achieved results are analysed and the discrepancies from some reference LiDAR data are computed for a final evaluation.

Photogrammetric Modelling for Urban Medieval Site Mapping. A Case Study from Curtea de Argeş, Romania

“…All the UAv frames were imported into ContextCapture v4 by Bentley Systems, a dedicated UAV photogrammetric software (Nex, Remondino 2014, Aicardi et al 2016. The geotagged images were automatically aligned and adjusted with the help of GCPs collected on the field.…”

Uav Photgrammetric Workflows: A Best Practice Guideline

“…Special Task UAVs (combat/decoys systems) (Nex and Remondino, 2014) The dissertation of Eisenbeiss provides an alternate way in which UAVs can be classified, which is by being considered as unpowered or powered, as well as lighter than air or heavier than air (Eisenbeiß, 2009 (Eisenbeiß, 2009) From the literature explored throughout this review, in relation to variables such as low cost and usability, the most common platform used for aerial photogrammetry are rotary wing aircraft. Specifically, multi-rotors, which include quadcopters, hexacopters, and octocopters, were seen in the articles read (Aicardi et al, 2016;Bolognesi et al, 2015;Bolognesi et al, 2014;Faltýnová et al, 2016;Fiorillo et al, 2013;Hashim et al, 2012;Stek, 2016;Sun and Cao, 2015).…”

“…These are nadir (camera positioned vertically) and oblique (camera positioned on an angle). At first, UAV photogrammetry was used mostly with nadir images for the creation of Digital Terrain (or Surface) Models (Aicardi et al, 2016). This was because there was not enough information with these nadir images to successfully capture details of facades.…”

“…Automatic image acquisition can be done through software such as the Pix4D app, but is only useful for nadir images as the camera angle is not changed by the software. Additionally, flights are usually done in linear or circular patterns to capture information to ensure consistent overlap (Aicardi et al, 2016). …”

“…These involved: complimenting the initial survey by capturing inaccessible roof areas or facades over 4 floors (Faltýnová et al, 2016), or using the UAV to complete the survey in its entirety (Aicardi et al, 2016;Bolognesi et al, 2015;Xu et al, 2016). …”