Investigation of Fish-Eye Lenses for Small-UAV Aerial Photography

Abstract

Abstract-Aerial photography obtained by unmanned aerial vehicles (UAVs) is a rising market for their civil application. Small UAVs are believed to close gaps in niche markets, such as acquiring airborne image data for remote sensing purposes. Small UAVs can fly at low altitudes, in dangerous environments, and over long periods of time. However, their small lightweight construction leads to new problems, such as higher agility and more susceptibility to turbulence, which has a big impact on the quality of the data and their suitability for aerial photography. This paper investigates the use of fish-eye lenses to overcome field-of-view (FOV) issues for highly agile UAV platforms susceptible to turbulence. The fish-eye lens has the benefit of a large observation area (large FOV) and does not add additional weight to the aircraft, such as traditional mechanical stabilizing systems. We present the implementation of a fish-eye lens for aerial photography and mapping purposes, with potential use in remote sensing applications. We describe a detailed investigation from the fish-eye lens distortion to the registering of the images. Results of the process are presented using low-quality sensors typically found on small UAVs. The system was flown on a midsize platform (a more stable Cessna aircraft) and also on ARCAA's small (< 10 kg) UAV platform. The effectiveness of the approach is compared for the two sized platforms.

Radiometric and Geometric Analysis of Hyperspectral Imagery Acquired from an Unmanned Aerial Vehicle

“…Because the PIKA II records at a higher rate than the GPS/INS, an interpolation method is used in GeoReg to link the GPS and image data, resulting in georegistration errors. Incorporation of a fiber-optic gyroscope could improve results; however, as Gurtner et al [37] state, this would be counter to the low-cost nature of the intended approach.…”

Remote Sensing of Submerged Aquatic Vegetation in a Shallow Non-Turbid River Using an Unmanned Aerial Vehicle

“…However, wide-angle or fish-eye lenses are often needed to overcome the height and stability limitations of small UAV [41]. As a consequence, the GoPro wide-angle sensor provides information over a larger spatial area, with the drawback of added distortion on the edge of the image.…”

“…As a consequence, the GoPro wide-angle sensor provides information over a larger spatial area, with the drawback of added distortion on the edge of the image. Software subsequently can be used to remove distortion and correct the image back to a rectilinear lens projection [41]. The camera was mounted in a vertical position under the UAV; the only modification being drilling two small holes in a plastic mount to match the UAV thread pattern.…”

“…UAVs have been successfully applied for natural resource assessment, environmental monitoring, forest inventories, surveying, river corridor monitoring, plume tracking, wildlife management, avalanche patrols, and precision agriculture [33][34][35]37]; along with law enforcement, firefighting, border patrol, disaster relief, and search and rescue [40]. UAV use in mapping SAV for freshwater benthic ecology would also seem promising given widespread civilian and commercial use [33,35,41,42].…”

The Geometry and Usage of the Supplementary Fisheye Lenses in Smartphones

“…[53], authors have focused on dioptric systems to implement a robot surveillance application for fast and robust tracking of moving objects in dynamic, unknown environments. Another application that uses fisheye lens is a research that examines the use of fisheye lenses as optical sensors on unmanned aerial vehicle (UAV) platform in Queensland Technical University in Australia [54]. Grelsson [55] used a fisheye camera for horizon detection in aerial images.…”