Abstract
Abstract. Fisheye camera installed on-board mass market UAS are becoming very popular and it is more and more frequent the use of such platforms for photogrammetric purposes. The interest of wide-angles images for 3D modelling is confirmed by the introduction of fisheye models in several commercial software packages. The paper exploits the different mathematical models implemented in the most famous commercial photogrammetric software packages, highlighting the different processing pipelines and analysing the achievable results in terms of checkpoint residuals, as well as the quality of the delivered 3D point clouds. A two-step approach based on the creation of undistorted images has been tested too. An experimental test has been carried out using a Parrot Bebop 2 UAS by performing a flight over an historical complex located near Piacenza (Northern Italy), which is characterized by the simultaneous presence of horizontal, vertical and oblique surfaces. Different flight configurations have been tested to evaluate the potentiality and possible drawbacks of the previously mentioned UAS platform. Results confirmed that the fisheye images acquired with the Parrot Bebop 2 are suitable for 3D modelling, ensuring accuracies of the photogrammetric blocks of the order of the GSD (about 0.05 m normal to the optic axis in case of a flight height equal to 35 m). The generated point clouds have been compared to a reference scan, acquired by means of a MS60 MultiStation, resulting in differences below 0.05 in all directions.
Highlights
The use of fisheye camera has becoming very popular because of their great advantages in terms of field of view, if compared to the one of rectilinear cameras, coupled with their low-cost market availability
Different fisheye mathematical models have been exploited, paying specific attention to those implemented in Pix4D Mapper Pro, Agisoft PhotoScan and to the new fisheye calibration and image correction functions embedded in Matlab 2017b
The residuals of the checkpoints are below the Ground Sample Distance (GSD) in all the directions, for all the tested flight configurations
Summary
The use of fisheye camera has becoming very popular because of their great advantages in terms of field of view, if compared to the one of rectilinear cameras, coupled with their low-cost market availability These systems were commercialized for entertainment purposes (e.g. photography, realization of personal or commercial videos), but recently they have been installed on several Unmanned Aerial Systems (UAS), which are more and more often used for photogrammetric purposes too. The presence of an oblique camera on-board represents a challenge for classical photogrammetric software packages, but it is very interesting because it allows overcoming the occlusion problems that are typical of nadir flights This task has been addressed by the Italian Society of Photogrammetry and Topography (SIFET) dedicating a benchmark to analyze the potential and critical aspects of the use of UAS oblique images.
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