Airborne Optical Sectioning for Nesting Observation

Abstract

We describe how a new and low-cost aerial scanning technique, airborne optical sectioning (AOS), can support ornithologists in nesting observation. After capturing thermal and color images during a seven minutes drone flight over a 40 × 12 m patch of the nesting site of Austria’s largest heron population, a total of 65 herons and 27 nests could be identified, classified, and localized in a sparse 3D reconstruction of the forest. AOS is a synthetic aperture imaging technique that removes occlusion caused by leaves and branches. It registers recorded images to a common 3D coordinate system to support the reconstruction and analysis of the entire forest volume, which is impossible with conventional 2D or 3D imaging techniques. The recorded data is published with open access.

Acceleration-Aware Path Planning with Waypoints

“…Objects of interest (people in search and rescue scenario) at a particular distance often remain occluded by the occluders (such as forests). Airborne optical sectioning (AOS) is a wide synthetic-aperture aerial imaging technique that applies camera drones for the real-time removal of occlusion caused by vegetation, such as forests [15,[17][18][19][20][21][22][23][24][25]. It has been demonstrated as a capable and effective tool in various applications (such as archaeology [17], wildlife observation [21], and search and rescue [15,24]).…”

“…Airborne optical sectioning (AOS) is a wide synthetic-aperture aerial imaging technique that applies camera drones for the real-time removal of occlusion caused by vegetation, such as forests [15,[17][18][19][20][21][22][23][24][25]. It has been demonstrated as a capable and effective tool in various applications (such as archaeology [17], wildlife observation [21], and search and rescue [15,24]). AOS' efficiency concerning the occlusion density, occluder sizes, number of integrated samples, and size of the synthetic aperture has been explained by employing a Drones 2021, 5, 143 2 of 18 randomly distributed statistical model [19,25].…”

“…(b) Wide synthetic aperture imaging principle with AOS for search and rescue purposes. Single images captured through a large scan are computationally integrated (registered to the ground surface and averaged) to remove occlusion [15,[17][18][19][20][21][22][23][24][25]. (c) Occlusion removal result with AOS: thermal signature of occluded people in single images is quite similar to that of trees.…”

Combined person classification with airborne optical sectioning

“…It acquires individual signals of multiple or a single moving small-aperture sensor to computationally combine them to improve, for instance, resolution, depth of field, frame rate, contrast, or signal-to-noise ratio. SA sensing has been utilized with diverse sensors in a wide range of applications, such as radar 1-3 (obtaining weather-independent images and reconstructing geospatial depth), radio telescopes 4,5 (observing large celestial phenomena in outer space), microscopes 6 (reconstructing a defocus-free 3D volume using interferometry), sonar 7-10 (generating high-resolution mappings of underwater objects and seafloors), ultrasound 11,12 (non-intrusive intravascular 3D imaging), laser 13,14 (earth observation utilizing shorter wavelengths using LiDAR), and optical imaging [15][16][17][18][19][20][21][22] (acquiring structured light fields with large camera arrays for various post-processing steps, such as refocusing, computation of virtual views with maximal synthetic apertures, and varying depth of field).Airborne optical sectioning (AOS) [23][24][25][26][27][28][29][30][31] is an effective wide-synthetic-aperture aerial imaging technique that can be deployed using camera drones. It allows virtual mimicking of a wide aperture optic of the shape and size of the scan area (possibly hundreds to thousands of square meters) that generates images of an extremely shallow depth of field above an occluding structure, such as a forest.…”

“…Airborne optical sectioning (AOS) [23][24][25][26][27][28][29][30][31] is an effective wide-synthetic-aperture aerial imaging technique that can be deployed using camera drones. It allows virtual mimicking of a wide aperture optic of the shape and size of the scan area (possibly hundreds to thousands of square meters) that generates images of an extremely shallow depth of field above an occluding structure, such as a forest.…”